[top]
000
FXUS63 KDMX 272357
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
555 PM CST FRI FEB 27 2009
.SHORT TERM.../TONIGHT THROUGH MON NIGHT/
MAIN CONCERN TONIGHT IS THE IMPENDING SYSTEM MOVING ACROSS NEBRASKA
AT THE MOMENT THAT WILL PUSH INTO FAR WESTERN IOWA THIS EVENING AND
INTO CENTRAL IOWA AFT ABOUT 02Z. THERE ARE A COUPLE OF CAVEATS TO
THE FORECAST FOR CENTRAL IOWA THAT DIFFER SOMEWHAT FROM FURTHER
WEST. PER FORECAST SOUNDINGS...OMA SATURATES THROUGH 700 MB RAPIDLY
LATE THIS AFTERNOON AND I EXPECT TO SEE SNOW DEVELOPING THIS EARLY
EVENING ON OUR DOORSTEP. HOWEVER...THE AIRMASS OVER CENTRAL IOWA IS
SOMEWHAT DRIER AND WILL TAKE A BIT MORE TIME TO SATURATE. MOISTURE
IN PLACE BY 03-06Z.
AS FOR DYNAMICS...WHATS INTERESTING ABOUT THIS IS THAT THERE IS LOW
LEVEL FRONTOGENETICAL FORCING BUT ALMOST NIL IN
THE MID LEVELS. LIFT ABOVE AND BELOW THE DENDRITIC LAYER EXISTS BUT
AT DIFFERENT TIMES AND OF MARGINAL INTENSITY AND THE LIFT REALLY
DOESN`T COME TOGETHER IN THE DENDRITIC LAYER EXCEPT FOR A NARROW
WINDOW BETWEEN 03Z AND 06Z. AGAIN...THESE PARAMETERS ARE BETTER TO
THE WEST. LOOKING AT SNOWFALL RATIOS THE COBB OUTPUT WAS A LITTLE
MORE BULLISH HERE AND THE SREF GENERALLY 15 TO 20:1 WITH THE HIGHER
RATIOS COMING IN A TIME WHEN SNOWFALL WONT GET GOING GOOD...IN THE
NORTHWEST. TAKING ALL THIS INTO CONSIDERATION...I BLENDED SNOWFALL
RATIOS BETWEEN SREF AND COBB OUTPUTS AND I ADJUSTED QPF TO ACCOUNT
FOR THE DRIER AIR INITIALLY. THIS RESULTED IN SOME ADJUSTMENT TO
SNOWFALL AMOUNTS. A NARROW BAND OF 3 TO 4 INCHES OCCURS OVER MY FAR
WESTERN BORDER AND A SNOW ADVISORY WILL BE ISSUED FOR THE 3-4 INCH
SNOW BAND. ELSEWHERE...SNOWFALL WILL BE IN THE 1-2 INCH RANGE WITH
BULK OF THE SNOWFALL OCCURRING FROM 03Z-09Z THEN PULLING OFF TO THE
SOUTHEAST. ALSO LOWERED TEMPS TONIGHT AS SOME PRETTY COLD AIR GETS
DRAWN DOWN ON THE BACK SIDE OF THIS FEATURE.
FORCING FROM SYSTEM TONIGHT SHOULD BE JUST EXITING SRN IA AROUND 12Z
WITH ANY ADDITIONAL ACCUMULATIONS LESS THAN AN INCH. SKIES SHOULD
THEN CLEAR LATER IN THE AFTERNOON IN DRY NW FLOW AS ELONGATED SFC
HIGH PRESSURE AREA SETTLES INTO MO VALLEY. THIS WILL RESULT IN FAIR
AND COOL WX THROUGH THE WEEKEND INTO EARLY NEXT WEEK.
AS HAS OFTEN BEEN THE CASE THIS SEASON...GFS HAS NOT CAPTURED
MAGNITUDE OF COLDER AIRMASS UPSTREAM SO HAVE LEANED TOWARD COOLER
NAM MOS THROUGH THE WEEKEND. THEN MODERATED IT TOWARD MORE OF A
BLEND INTO MON. ALSO CLIPPED A FEW DEGREES OFF SOUTHWESTERN
SECTIONS DUE TO PROJECTED SNOW COVER.
.LONG TERM.../TUE THROUGH FRI/
THIS PERIOD SHOULD BE RELATIVELY UNEVENTFUL AS WELL OUTSIDE OF
INCREASING PRECIP CHANCES TOWARDS DAYS SIX AND SEVEN. MODELS QUITE
SIMILAR WITH SAME GENERAL SCENARIOS SO WILL CONTINUE TO FOLLOW A
BLEND. FAIR WEATHER AND SEASONAL TEMPS TUE/WED WITH APPROACH OF
CENTRAL CONUS RIDGE. THE INCREASING WARM ADVECTION AND ULTIMATE
PASSAGE OF STRONGER SHORT WAVE AND SFC REFLECTION THU OR FRI WILL
BRING AT LEAST SOME SHOWERS BUT TIMING AND LOCATION OBVIOUSLY
DIFFICULT TO PIN DOWN AT THIS POINT...THUS ONLY CHANCE POPS. THERE
IS SOME HINT AT THUNDER POTENTIAL AS WELL...BUT CONFIDENCE NOT GREAT
ENOUGH TO INCLUDE AT THIS TIME. NO REAL DEVIATION FROM GUIDANCE
WITH WARMING TREND AND ABOVE NORMAL TEMPS BY THE END OF THE PERIOD.
&&
.AVIATION...28/00Z
STRONG S/WV DROPPING SEWD OUT OF SD WILL MOVE ACRS ERN KS BY 18Z.
IMPRESSIVE CLOUD AND SNOW SHIELD DROPPING SEWD AND WILL MAINLY
AFFECT KFOD-KDSM SWWD. DROPED TO IFR CONDS AT TIMES AT THESE
LOCATIONS. THE NERN TAFS WILL SEE LTL OR NO AFFECT FM THE SYS WITH
SOME LOW AND MID CLDS FOR A WHILE. SYS WILL MOVE OUT RPDLY WITH
CLRG SPRDG SEWD ACRS THE TAF SITES SAT MRNG...DECENT VFR CONDS BY
AFTN.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...WINTER WX ADVY 02Z-12Z
CRAWFORD-CARROLL-AUDUBON-GUTHRIE-CASS-ADIAR-MADISON-ADAMS-UNION-
CLARKE-TAYLOR-RINGGOLD-DECATUR
&&
$$
FAB/BSS/MS FEB 09
000
FXUS63 KDMX 272111
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
310 PM CST FRI FEB 27 2009
.SHORT TERM.../TONIGHT THROUGH MON NIGHT/
MAIN CONCERN TONIGHT IS THE IMPENDING SYSTEM MOVING ACROSS NEBRASKA
AT THE MOMENT THAT WILL PUSH INTO FAR WESTERN IOWA THIS EVENING AND
INTO CENTRAL IOWA AFT ABOUT 02Z. THERE ARE A COUPLE OF CAVEATS TO
THE FORECAST FOR CENTRAL IOWA THAT DIFFER SOMEWHAT FROM FURTHER
WEST. PER FORECAST SOUNDINGS...OMA SATURATES THROUGH 700 MB RAPIDLY
LATE THIS AFTERNOON AND I EXPECT TO SEE SNOW DEVELOPING THIS EARLY
EVENING ON OUR DOORSTEP. HOWEVER...THE AIRMASS OVER CENTRAL IOWA IS
SOMEWHAT DRIER AND WILL TAKE A BIT MORE TIME TO SATURATE. MOISTURE
IN PLACE BY 03-06Z.
AS FOR DYNAMICS...WHATS INTERESTING ABOUT THIS IS THAT THERE IS LOW
LEVEL FRONTOGENETICAL FORCING BUT ALMOST NIL IN
THE MID LEVELS. LIFT ABOVE AND BELOW THE DENDRITIC LAYER EXISTS BUT
AT DIFFERENT TIMES AND OF MARGINAL INTENSITY AND THE LIFT REALLY
DOESN`T COME TOGETHER IN THE DENDRITIC LAYER EXCEPT FOR A NARROW
WINDOW BETWEEN 03Z AND 06Z. AGAIN...THESE PARAMETERS ARE BETTER TO
THE WEST. LOOKING AT SNOWFALL RATIOS THE COBB OUTPUT WAS A LITTLE
MORE BULLISH HERE AND THE SREF GENERALLY 15 TO 20:1 WITH THE HIGHER
RATIOS COMING IN A TIME WHEN SNOWFALL WONT GET GOING GOOD...IN THE
NORTHWEST. TAKING ALL THIS INTO CONSIDERATION...I BLENDED SNOWFALL
RATIOS BETWEEN SREF AND COBB OUTPUTS AND I ADJUSTED QPF TO ACCOUNT
FOR THE DRIER AIR INITIALLY. THIS RESULTED IN SOME ADJUSTMENT TO
SNOWFALL AMOUNTS. A NARROW BAND OF 3 TO 4 INCHES OCCURS OVER MY FAR
WESTERN BORDER AND A SNOW ADVISORY WILL BE ISSUED FOR THE 3-4 INCH
SNOW BAND. ELSEWHERE...SNOWFALL WILL BE IN THE 1-2 INCH RANGE WITH
BULK OF THE SNOWFALL OCCURRING FROM 03Z-09Z THEN PULLING OFF TO THE
SOUTHEAST. ALSO LOWERED TEMPS TONIGHT AS SOME PRETTY COLD AIR GETS
DRAWN DOWN ON THE BACK SIDE OF THIS FEATURE.
FORCING FROM SYSTEM TONIGHT SHOULD BE JUST EXITING SRN IA AROUND 12Z
WITH ANY ADDITIONAL ACCUMULATIONS LESS THAN AN INCH. SKIES SHOULD
THEN CLEAR LATER IN THE AFTERNOON IN DRY NW FLOW AS ELONGATED SFC
HIGH PRESSURE AREA SETTLES INTO MO VALLEY. THIS WILL RESULT IN FAIR
AND COOL WX THROUGH THE WEEKEND INTO EARLY NEXT WEEK.
AS HAS OFTEN BEEN THE CASE THIS SEASON...GFS HAS NOT CAPTURED
MAGNITUDE OF COLDER AIRMASS UPSTREAM SO HAVE LEANED TOWARD COOLER
NAM MOS THROUGH THE WEEKEND. THEN MODERATED IT TOWARD MORE OF A
BLEND INTO MON. ALSO CLIPPED A FEW DEGREES OFF SOUTHWESTERN
SECTIONS DUE TO PROJECTED SNOW COVER.
.LONG TERM.../TUE THROUGH FRI/
THIS PERIOD SHOULD BE RELATIVELY UNEVENTFUL AS WELL OUTSIDE OF
INCREASING PRECIP CHANCES TOWARDS DAYS SIX AND SEVEN. MODELS QUITE
SIMILAR WITH SAME GENERAL SCENARIOS SO WILL CONTINUE TO FOLLOW A
BLEND. FAIR WEATHER AND SEASONAL TEMPS TUE/WED WITH APPROACH OF
CENTRAL CONUS RIDGE. THE INCREASING WARM ADVECTION AND ULTIMATE
PASSAGE OF STRONGER SHORT WAVE AND SFC REFLECTION THU OR FRI WILL
BRING AT LEAST SOME SHOWERS BUT TIMING AND LOCATION OBVIOUSLY
DIFFICULT TO PIN DOWN AT THIS POINT...THUS ONLY CHANCE POPS. THERE
IS SOME HINT AT THUNDER POTENTIAL AS WELL...BUT CONFIDENCE NOT GREAT
ENOUGH TO INCLUDE AT THIS TIME. NO REAL DEVIATION FROM GUIDANCE
WITH WARMING TREND AND ABOVE NORMAL TEMPS BY THE END OF THE PERIOD.
&&
.AVIATION...27/18Z
IMPRESSIVE SYSTEM PUSHING OUT OF THE HIGH PLAINS ALREADY SPREADING
SNOW ACROSS CENTRAL NEBRASKA. MODELS COMING INTO MORE AGREEMENT ON
THE TRACK OF THE HEAVIEST SNOW. THAT AREA BEING OVER WRN AND SW
IA. THE TAF SITES MOST AFFECTED WOULD BE KFOD AND KDSM BEING ON THE
FRINGE OF THE HEAVIER SNOW. SNOWFALL AMOUNTS ALONG THIS LINE AND
WEST WILL BE AROUND 2-3 INCHES. MVFR/IFR COND WILL OVERSPREAD
THE WRN HALF OF CENTRAL IOWA DURING THE EVENING WITH SNOW STARTING
BETWEEN 03-06Z. I EXPECT MVFR/IFR CONDITIONS TO OVERSPREAD ALL TAF
SITES AFT 06Z BUT SNOW SHOULD NOT BE PREVALENT N AND E OF A KMCW
KCNC LINE.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...WINTER WX ADVY 02Z-12Z
CRAWFORD-CARROLL-AUDUBON-GUTHRIE-CASS-ADIAR-MADISON-ADAMS-UNION-
CLARKE-TAYLOR-RINGGOLD-DECATUR
&&
$$
FAB/BSS
[top]
000
FXUS63 KDVN 272057 AAA
AFDDVN
AREA FORECAST DISCUSSION...UPDATED TO ADD HYDRO SECTION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CST FRI FEB 27 2009
.SYNOPSIS...
CANADIAN HIGH PRESSURE CENTERED OVER EASTERN ND WILL MOVE TO THE
GREAT LAKES BY SATURDAY. THIS WILL FEED DRIER NORTH TO NORTHEAST
WINDS INTO THE NORTHERN PORTIONS OF THE DVN CWA. MEANWHILE...UPPER
LEVEL LOW PRESSURE IN THE WESTERN HIGH PLAINS CURRENTLY SPREADING
LIGHT TO MODERATE SNOWS INTO WESTERN SD INTO NEB. THIS FEATURE TO
TRACK SOUTHWEST OF OUR REGION AS IT JOURNEY/S INTO THE LOWER
MISSISSIPPI VALLEY. THEN THE PERIOD FROM SATURDAY NIGHT THROUGH
WEDNESDAY LOOKS DRY WITH A GRADUAL WARMING TREND. THE NEXT STORM
SYSTEM TO POSSIBLY BRING MODERATE RAINS LATE NEXT WEEK.
&&
.SHORT TERM...TONIGHT AND SATURDAY...
CANADIAN HIGH PRESSURE OVER ND FEEDING DRIER AIR INTO OUR NORTHERN
CWA ON NORTH TO NORTHEAST WINDS. CLEARING LINE HAS PUSHED TO ABOUT
HIGHWAY 30 BUT HAS NEARLY STOPPED. AS THE HIGH SHIFTS INTO THE GREAT
LAKES AREA BY SATURDAY THE DRY FEED WILL CONTINUE. IN THE MEANTIME
UPPER LEVEL LOW PRESSURE CURRENTLY IN THE WESTERN HIGH PLAINS IS
SPREADING LIGHT TO MODERATE SNOWS ACROSS WESTERN SD AND MUCH OF NEB.
THIS LOW IS PROGGED BY THE GFS/ECMWF/UKMET TO TRACK INTO KS AND THEN
THE LOWER MISSISSIPPI VALLEY THROUGH SATURDAY. THIS SETS UP THE
CLASSIC BATTLE BETWEEN THE DRIER AIR FROM THE NORTH VS MOISTURE
ASSOCIATED WITH THE STORM SYSTEM TO THE SOUTHWEST. WILL CONTINUE THE
IDEA OF ONLY THE SOUTHWEST CWA HAVING A PERIOD OF LIGHT SNOW WITH
ACCUMULATIONS OF AN INCH OR LESS LATE TONIGHT INTO EARLY SATURDAY.
THIS WILL BE SOUTHWEST OF A LINE FROM VINTON TO FORT MADISON.
EVENTUALLY AS THE STORM SYSTEM DROPS SOUTH OF THE REGION AND THE
GREAT LAKES HIGH TAKES OVER...SKIES SHOULD BE GRADUALLY CLEARING
FROM THE NORTH IN THE AFTERNOON. HOWEVER...NORTH WINDS COMING OFF
THE FRESH 6 TO 10 INCH SNOW PACK ACROSS SOUTHERN MN TO CENTRAL WI
WILL KEEP OUR TEMPS CHILLY. IN FACT MAX TEMPS ON SATURDAY WILL BE
SOME 10 TO 15 DEGREES BELOW NORMAL FOR THE LAST DAY OF FEBRUARY.
..HAASE..
.LONG TERM...SATURDAY NIGHT THROUGH NEXT FRIDAY...
MARCH SET TO COME IN LIKE A LAMB AS SFC RIDGE AXIS SETTLES INTO
REGION SAT NGT INTO MON WITH CANADIAN HIGH BUILDING DOWN THROUGH THE
GREAT LAKES. RESULT WILL BE DRY WX WITH TEMPS NEAR TO BELOW NORMAL.
GFS AND ECMWF FOR PAST COUPLE OF RUNS HAVE BEEN SHOWING ENERGY
TOPPING ROCKIES UPPER RIDGE AND DIVING DOWN INTO GREAT LAKES ON
MON/MON EVE WITH SOME LIGHT QPF. BOTH MODELS HOWEVER DAMPEN FEATURE
AS IT ENCOUNTERS CONFLUENT FLOW AND THIS ALONG WITH DRY LOW LEVEL
NORTHEAST FETCH BENEATH GREAT LAKES HIGH WILL PRECLUDE ANY MENTION
OF PCPN MON PM/NGT. TEMPS MODERATE MID TO LATE NEXT WEEK IN ADVANCE
OF PACIFIC ENERGY. MODELS TO NO SURPRISE HAVE BEEN TRENDING SLOWER.
GULF WIDE OPEN FOR FEW DAYS TO ALLOW GOOD MOISTURE FEED FOR MODERATE
TO LOCALLY HEAVY PCPN EVENT THURS/THURS NGT. BAROCLINICITY AND JET
WITH TRACK OF SYSTEM THOUGH SUPPORT THIS BEING TO OUR NORTH WITH
LIGHT TO MODERATE AMOUNTS FOR THE CWA. WILL TAKE FEW MORE DAYS TO
PIN DOWN. IF SLOWING TREND CONTINUES WILL NEED TO EXPAND POPS INTO
FRI. ..MCCLURE..
&&
.AVIATION...
FROM ABOUT HIGHWAY 30 SOUTHWARD MVFR CIGS SHOULD CONTINUE THROUGH
TONIGHT. EXPECT A PERIOD OF LIGHT SNOW AFTER MIDNIGHT INTO EARLY
SATURDAY FOR AREAS WEST AND SOUTHWEST OF THE TAF SITES. KDBQ SHOULD
HAVE VFR CONDITIONS WITH ONLY SOME MID AND HIGH LEVEL CLOUDS. ON
SATURDAY AFTERNOON SKIES SHOULD GRADUALLY CLEAR FROM THE NORTH.
EXPECT NORTH TO NORTHEAST WINDS 10 TO 15 KNOTS TO CONTINUE THROUGH
SATURDAY.
..HAASE..
&&
.HYDROLOGY...
CANCELLED FLOOD WARNING FOR GREEN RIVER NEAR GENESEO. INTENSE NATURE
OF THE RAINFALL LAST NIGHT LEADING TO EARLIER CRESTS WITH LOWER
VOLUME NOTED THAN MODELED PER COORD WITH NCRFC. THIS LOWER VOLUME OF
WATER LIKELY TO HAVE IMPACTS ON PORTIONS OF ROCK RIVER WITH LOWER
CRESTS THAN CURRENTLY FCST.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
HAASE/MCCLURE
000
FXUS63 KDVN 272045
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 PM CST FRI FEB 27 2009
.SYNOPSIS...
CANADIAN HIGH PRESSURE CENTERED OVER EASTERN ND WILL MOVE TO THE
GREAT LAKES BY SATURDAY. THIS WILL FEED DRIER NORTH TO NORTHEAST
WINDS INTO THE NORTHERN PORTIONS OF THE DVN CWA. MEANWHILE...UPPER
LEVEL LOW PRESSURE IN THE WESTERN HIGH PLAINS CURRENTLY SPREADING
LIGHT TO MODERATE SNOWS INTO WESTERN SD INTO NEB. THIS FEATURE TO
TRACK SOUTHWEST OF OUR REGION AS IT JOURNEY/S INTO THE LOWER
MISSISSIPPI VALLEY. THEN THE PERIOD FROM SATURDAY NIGHT THROUGH
WEDNESDAY LOOKS DRY WITH A GRADUAL WARMING TREND. THE NEXT STORM
SYSTEM TO POSSIBLY BRING MODERATE RAINS LATE NEXT WEEK.
&&
.SHORT TERM...TONIGHT AND SATURDAY...
CANADIAN HIGH PRESSURE OVER ND FEEDING DRIER AIR INTO OUR NORTHERN
CWA ON NORTH TO NORTHEAST WINDS. CLEARING LINE HAS PUSHED TO ABOUT
HIGHWAY 30 BUT HAS NEARLY STOPPED. AS THE HIGH SHIFTS INTO THE GREAT
LAKES AREA BY SATURDAY THE DRY FEED WILL CONTINUE. IN THE MEANTIME
UPPER LEVEL LOW PRESSURE CURRENTLY IN THE WESTERN HIGH PLAINS IS
SPREADING LIGHT TO MODERATE SNOWS ACROSS WESTERN SD AND MUCH OF NEB.
THIS LOW IS PROGGED BY THE GFS/ECMWF/UKMET TO TRACK INTO KS AND THEN
THE LOWER MISSISSIPPI VALLEY THROUGH SATURDAY. THIS SETS UP THE
CLASSIC BATTLE BETWEEN THE DRIER AIR FROM THE NORTH VS MOISTURE
ASSOCIATED WITH THE STORM SYSTEM TO THE SOUTHWEST. WILL CONTINUE THE
IDEA OF ONLY THE SOUTHWEST CWA HAVING A PERIOD OF LIGHT SNOW WITH
ACCUMULATIONS OF AN INCH OR LESS LATE TONIGHT INTO EARLY SATURDAY.
THIS WILL BE SOUTHWEST OF A LINE FROM VINTON TO FORT MADISON.
EVENTUALLY AS THE STORM SYSTEM DROPS SOUTH OF THE REGION AND THE
GREAT LAKES HIGH TAKES OVER...SKIES SHOULD BE GRADUALLY CLEARING
FROM THE NORTH IN THE AFTERNOON. HOWEVER...NORTH WINDS COMING OFF
THE FRESH 6 TO 10 INCH SNOW PACK ACROSS SOUTHERN MN TO CENTRAL WI
WILL KEEP OUR TEMPS CHILLY. IN FACT MAX TEMPS ON SATURDAY WILL BE
SOME 10 TO 15 DEGREES BELOW NORMAL FOR THE LAST DAY OF FEBRUARY.
..HAASE..
.LONG TERM...SATURDAY NIGHT THROUGH NEXT FRIDAY...
MARCH SET TO COME IN LIKE A LAMB AS SFC RIDGE AXIS SETTLES INTO
REGION SAT NGT INTO MON WITH CANADIAN HIGH BUILDING DOWN THROUGH THE
GREAT LAKES. RESULT WILL BE DRY WX WITH TEMPS NEAR TO BELOW NORMAL.
GFS AND ECMWF FOR PAST COUPLE OF RUNS HAVE BEEN SHOWING ENERGY
TOPPING ROCKIES UPPER RIDGE AND DIVING DOWN INTO GREAT LAKES ON
MON/MON EVE WITH SOME LIGHT QPF. BOTH MODELS HOWEVER DAMPEN FEATURE
AS IT ENCOUNTERS CONFLUENT FLOW AND THIS ALONG WITH DRY LOW LEVEL
NORTHEAST FETCH BENEATH GREAT LAKES HIGH WILL PRECLUDE ANY MENTION
OF PCPN MON PM/NGT. TEMPS MODERATE MID TO LATE NEXT WEEK IN ADVANCE
OF PACIFIC ENERGY. MODELS TO NO SURPRISE HAVE BEEN TRENDING SLOWER.
GULF WIDE OPEN FOR FEW DAYS TO ALLOW GOOD MOISTURE FEED FOR MODERATE
TO LOCALLY HEAVY PCPN EVENT THURS/THURS NGT. BAROCLINICITY AND JET
WITH TRACK OF SYSTEM THOUGH SUPPORT THIS BEING TO OUR NORTH WITH
LIGHT TO MODERATE AMOUNTS FOR THE CWA. WILL TAKE FEW MORE DAYS TO
PIN DOWN. IF SLOWING TREND CONTINUES WILL NEED TO EXPAND POPS INTO
FRI. ..MCCLURE..
&&
.AVIATION...
FROM ABOUT HIGHWAY 30 SOUTHWARD MVFR CIGS SHOULD CONTINUE THROUGH
TONIGHT. EXPECT A PERIOD OF LIGHT SNOW AFTER MIDNIGHT INTO EARLY
SATURDAY FOR AREAS WEST AND SOUTHWEST OF THE TAF SITES. KDBQ SHOULD
HAVE VFR CONDITIONS WITH ONLY SOME MID AND HIGH LEVEL CLOUDS. ON
SATURDAY AFTERNOON SKIES SHOULD GRADUALLY CLEAR FROM THE NORTH.
EXPECT NORTH TO NORTHEAST WINDS 10 TO 15 KNOTS TO CONTINUE THROUGH
SATURDAY.
..HAASE..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
HAASE/MCCLURE
000
FXUS63 KDMX 271807 AAB
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1147 AM CST FRI FEB 27 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM.../TODAY/
A LARGE AREA OF SURFACE HIGH PRESSURE WILL SLIDE FROM SOUTHERN
CANADA INTO NORTHERN MINNESOTA TODAY...BRINGING OUR WINDS AROUND TO
NORTHEAST BY THIS EVENING WITH ONLY SLOWLY DIMINISHING SPEEDS. THIS
WILL ALSO KEEP COLD AIR PUSHING IN FROM THE NORTH AND HOLD DOWN MAX
TEMPS. WIDESPREAD LOW CLOUDS AND SCATTERED FLURRIES EARLY THIS
MORNING SHOULD GRADUALLY CLEAR FROM NORTHWEST TO SOUTHEAST DURING
THE MORNING HOURS AS SUBSIDENCE AND DRIER AIR FROM THE HIGH TO THE
NORTH WORK THEIR WAY IN. MEANWHILE...A VIGOROUS MID-LEVEL SYSTEM
OVER THE NORTHERN ROCKIES AND PACIFIC NORTHWEST WILL MOVE QUICKLY
INTO THE GREAT PLAINS BY LATE THIS AFTERNOON...SPREADING SNOW ACROSS
MUCH OF SOUTH DAKOTA AND NEBRASKA...WITH THE SNOW APPROACHING OR
JUST ENTERING OUR FAR WESTERN COUNTIES BY 00Z.
.LONG TERM.../TONIGHT THROUGH THU/
PRIMARY FORECAST ISSUE DURING THE PERIOD WILL BE THE SYSTEM TONIGHT.
IMPRESSIVE LOOKING IMPULSE WITH SEVERAL EMBEDDED SHORTWAVES OVER
WYOMING AND IDAHO EARLY THIS MORNING WILL ARRIVE BY THIS EVENING.
SNOW WILL DEVELOP OVER THE SOUTHWESTERN HALF OF THE FORECAST AREA
THIS EVENING THEN WILL DROP SOUTH INTO MISSOURI BY SATURDAY MORNING.
SEEING SEVERAL NEGATIVES WITH THIS SYSTEM THAT COULD LIMIT SNOWFALL
AMOUNTS. FIRST...VERY DRY LOW LEVEL AIR IS DIPPING SOUTH IN THE WAKE
OF THE PREVIOUS SYSTEM AND THE DRY AIR IS FAIRLY DEEP...EXTENDING UP
TO AT LEAST 800 MB. THE INITIAL 2 TO 3 HOURS OF FORCING LIKELY WILL
BE SPENT SATURATING THE COLUMN OVER THE SOUTHWEST AND THE DRY AIR
MAY NOT BE OVERCOME AT ALL OVER THE NORTHEAST. SECOND...THIS SYSTEM
WILL NEED TO RELY ON PACIFIC MOISTURE THAT IS TAGGING ALONG WITH THE
GULF BEING CUT OFF FROM THE PREVIOUS SYSTEM AND THIS WILL FURTHER
COMPLICATE TIMELINESS OF SATURATION. THIRD...THE MAJORITY OF THE
FORCING IS IN THE -20C TO -30C REGION WHICH SUGGESTS PLATES AND
COLUMNS AS THE PRIMARY SNOW CRYSTAL. FINALLY...THE PRIMARY QG
FORCING REMAINS TO THE WEST AND ACROSS EASTERN NEBRASKA. WITH THE
ABOVE SAID...EVENT SHOULD BE SUB ADVISORY CRITERIA FOR MUCH OF THE
AREA WITH MAINLY 1 TO 3 INCHES OVER SOUTHWEST HALF AND AN INCH OR
LESS NORTHEAST.
THE SNOW WILL END EARLY SATURDAY OVER THE SOUTH THEN EXPECT A COOL
AND DRY REMAINDER OF THE WEEKEND. ARCTIC AIR IS JUST OFF TO THE
NORTH AND WILL AFFECT TEMPERATURES ESPECIALLY OVER THE NORTH WHERE
HIGHS WILL STRUGGLE TO GET ABOVE 20 BOTH DAYS. HIGH PRESSURE WILL
SHIFT EAST OF THE AREA BY MONDAY WITH RETURN FLOW DEVELOPING. HIGHS
IN THE 30S AND 40S WILL BE COMMON FOR THE EARLY PORTION OF THE WEEK.
&&
.AVIATION...27/18Z
IMPRESSIVE SYSTEM PUSHING OUT OF THE HIGH PLAINS ALREADY SPREADING
SNOW ACROSS CENTRAL NEBRASKA. MODELS COMING INTO MORE AGREEMENT ON
THE TRACK OF THE HEAVIEST SNOW. THAT AREA BEING OVER WRN AND SW
IA. THE TAF SITES MOST AFFECTED WOULD BE KFOD AND KDSM BEING ON THE
FRINGE OF THE HEAVIER SNOW. SNOWFALL AMOUNTS ALONG THIS LINE AND
WEST WILL BE AROUND 2-3 INCHES. MVFR/IFR COND WILL OVERSPREAD
THE WRN HALF OF CENTRAL IOWA DURING THE EVENING WITH SNOW STARTING
BETWEEN 03-06Z. I EXPECT MVFR/IFR CONDITIONS TO OVERSPREAD ALL TAF
SITES AFT 06Z BUT SNOW SHOULD NOT BE PREVALENT N AND E OF A KMCW
KCNC LINE.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/AVIATION...FAB
LONG TERM...DONAVON
000
FXUS63 KDVN 271714 AAA
AFDDVN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1114 AM CST FRI FEB 27 2009
.UPDATE...
CLEARING LINE THAT HAD BEEN DROPPING SOUTHWARD ACROSS OUR NORTHERN
CWA HAS NEARLY GROUND TO A HALT NEAR HIGHWAY 30. WITH UPPER AIR
ANALYSIS INDICATING COLD AIR ADVECTION AND A NORTHEAST SURFACE WIND
IT WILL BE TOUGH TO ERODE THE CLOUDS ANY FURTHER. HAVE ALSO LOWERED
MAX TEMPS FOR TODAY. UPPER LEVEL LOW IN THE NORTHERN ROCKIES PROGGED
TO DIVE SOUTHEAST INTO THE CENTRAL PLAINS AND THEN LOWER MISSISSIPPI
VALLEY THROUGH SATURDAY. OUR FAR SOUTHWEST CWA MAY GET GRAZED BY AN
AREA OF LIGHT SNOW ASSOCIATED WITH THIS SYSTEM. UPDATED GRIDS/ZFP
HAVE ALREADY BEEN SENT.
&&
.AVIATION...
MVFR CIGS EXPECTED REMAINDER OF TODAY AND TONIGHT AT KCID/KMLI/KBRL.
KDBQ WILL HAVE SKC THIS AFTERNOON WITH INCREASING MID AND HIGH LEVEL
CLOUDS OVERNIGHT. NORTH TO NORTHEAST WINDS 10-15 KNOTS.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
HAASE
000
FXUS63 KDMX 271130 AAA
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
530 AM CST FRI FEB 27 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM.../TODAY/
A LARGE AREA OF SURFACE HIGH PRESSURE WILL SLIDE FROM SOUTHERN
CANADA INTO NORTHERN MINNESOTA TODAY...BRINGING OUR WINDS AROUND TO
NORTHEAST BY THIS EVENING WITH ONLY SLOWLY DIMINISHING SPEEDS. THIS
WILL ALSO KEEP COLD AIR PUSHING IN FROM THE NORTH AND HOLD DOWN MAX
TEMPS. WIDESPREAD LOW CLOUDS AND SCATTERED FLURRIES EARLY THIS
MORNING SHOULD GRADUALLY CLEAR FROM NORTHWEST TO SOUTHEAST DURING
THE MORNING HOURS AS SUBSIDENCE AND DRIER AIR FROM THE HIGH TO THE
NORTH WORK THEIR WAY IN. MEANWHILE...A VIGOROUS MID-LEVEL SYSTEM
OVER THE NORTHERN ROCKIES AND PACIFIC NORTHWEST WILL MOVE QUICKLY
INTO THE GREAT PLAINS BY LATE THIS AFTERNOON...SPREADING SNOW ACROSS
MUCH OF SOUTH DAKOTA AND NEBRASKA...WITH THE SNOW APPROACHING OR
JUST ENTERING OUR FAR WESTERN COUNTIES BY 00Z.
.LONG TERM.../TONIGHT THROUGH THU/
PRIMARY FORECAST ISSUE DURING THE PERIOD WILL BE THE SYSTEM TONIGHT.
IMPRESSIVE LOOKING IMPULSE WITH SEVERAL EMBEDDED SHORTWAVES OVER
WYOMING AND IDAHO EARLY THIS MORNING WILL ARRIVE BY THIS EVENING.
SNOW WILL DEVELOP OVER THE SOUTHWESTERN HALF OF THE FORECAST AREA
THIS EVENING THEN WILL DROP SOUTH INTO MISSOURI BY SATURDAY MORNING.
SEEING SEVERAL NEGATIVES WITH THIS SYSTEM THAT COULD LIMIT SNOWFALL
AMOUNTS. FIRST...VERY DRY LOW LEVEL AIR IS DIPPING SOUTH IN THE WAKE
OF THE PREVIOUS SYSTEM AND THE DRY AIR IS FAIRLY DEEP...EXTENDING UP
TO AT LEAST 800 MB. THE INITIAL 2 TO 3 HOURS OF FORCING LIKELY WILL
BE SPENT SATURATING THE COLUMN OVER THE SOUTHWEST AND THE DRY AIR
MAY NOT BE OVERCOME AT ALL OVER THE NORTHEAST. SECOND...THIS SYSTEM
WILL NEED TO RELY ON PACIFIC MOISTURE THAT IS TAGGING ALONG WITH THE
GULF BEING CUT OFF FROM THE PREVIOUS SYSTEM AND THIS WILL FURTHER
COMPLICATE TIMELINESS OF SATURATION. THIRD...THE MAJORITY OF THE
FORCING IS IN THE -20C TO -30C REGION WHICH SUGGESTS PLATES AND
COLUMNS AS THE PRIMARY SNOW CRYSTAL. FINALLY...THE PRIMARY QG
FORCING REMAINS TO THE WEST AND ACROSS EASTERN NEBRASKA. WITH THE
ABOVE SAID...EVENT SHOULD BE SUB ADVISORY CRITERIA FOR MUCH OF THE
AREA WITH MAINLY 1 TO 3 INCHES OVER SOUTHWEST HALF AND AN INCH OR
LESS NORTHEAST.
THE SNOW WILL END EARLY SATURDAY OVER THE SOUTH THEN EXPECT A COOL
AND DRY REMAINDER OF THE WEEKEND. ARCTIC AIR IS JUST OFF TO THE
NORTH AND WILL AFFECT TEMPERATURES ESPECIALLY OVER THE NORTH WHERE
HIGHS WILL STRUGGLE TO GET ABOVE 20 BOTH DAYS. HIGH PRESSURE WILL
SHIFT EAST OF THE AREA BY MONDAY WITH RETURN FLOW DEVELOPING. HIGHS
IN THE 30S AND 40S WILL BE COMMON FOR THE EARLY PORTION OF THE WEEK.
&&
.AVIATION...27/12Z
LOW CLOUDS COVER MOST OF IOWA EARLY THIS MORNING...PRODUCING
PREVAILING MVFR CIGS AND ISOLATED FLURRIES ACROSS THE TAF
SITES...WITH BRIEF LOCAL IFR CIGS POSSIBLE AT KFOD AND KMCW IN THE
NEXT COUPLE OF HOURS. THE LOW CLOUDS WILL GRADUALLY CLEAR OUT FROM
NORTH TO SOUTH THIS MORNING...WITH VFR CONDITIONS PREVAILING AT MOST
LOCATIONS BY 16Z. NORTHERLY WINDS WILL ALSO BE SLOW TO DIMINISH
DURING THIS TIME. AS SURFACE HIGH PRESSURE MOVES INTO NORTHERN
MINNESOTA WINDS WILL TURN TO NORTHEAST AND DECREASE FURTHER THIS
AFTERNOON. AN APPROACHING MID-LEVEL STORM SYSTEM WILL BRING MVFR
CIGS BACK TO THE AREA FROM THE WEST THIS EVENING...AND SPREAD SNOW
MAINLY ACROSS THE SOUTHERN SITES TONIGHT.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/AVIATION...LEE
LONG TERM...DONAVON
000
FXUS63 KDMX 270920
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
320 AM CST FRI FEB 27 2009
.SHORT TERM.../TODAY/
A LARGE AREA OF SURFACE HIGH PRESSURE WILL SLIDE FROM SOUTHERN
CANADA INTO NORTHERN MINNESOTA TODAY...BRINGING OUR WINDS AROUND TO
NORTHEAST BY THIS EVENING WITH ONLY SLOWLY DIMINISHING SPEEDS. THIS
WILL ALSO KEEP COLD AIR PUSHING IN FROM THE NORTH AND HOLD DOWN MAX
TEMPS. WIDESPREAD LOW CLOUDS AND SCATTERED FLURRIES EARLY THIS
MORNING SHOULD GRADUALLY CLEAR FROM NORTHWEST TO SOUTHEAST DURING
THE MORNING HOURS AS SUBSIDENCE AND DRIER AIR FROM THE HIGH TO THE
NORTH WORK THEIR WAY IN. MEANWHILE...A VIGOROUS MID-LEVEL SYSTEM
OVER THE NORTHERN ROCKIES AND PACIFIC NORTHWEST WILL MOVE QUICKLY
INTO THE GREAT PLAINS BY LATE THIS AFTERNOON...SPREADING SNOW ACROSS
MUCH OF SOUTH DAKOTA AND NEBRASKA...WITH THE SNOW APPROACHING OR
JUST ENTERING OUR FAR WESTERN COUNTIES BY 00Z.
.LONG TERM.../TONIGHT THROUGH THU/
PRIMARY FORECAST ISSUE DURING THE PERIOD WILL BE THE SYSTEM TONIGHT.
IMPRESSIVE LOOKING IMPULSE WITH SEVERAL EMBEDDED SHORTWAVES OVER
WYOMING AND IDAHO EARLY THIS MORNING WILL ARRIVE BY THIS EVENING.
SNOW WILL DEVELOP OVER THE SOUTHWESTERN HALF OF THE FORECAST AREA
THIS EVENING THEN WILL DROP SOUTH INTO MISSOURI BY SATURDAY MORNING.
SEEING SEVERAL NEGATIVES WITH THIS SYSTEM THAT COULD LIMIT SNOWFALL
AMOUNTS. FIRST...VERY DRY LOW LEVEL AIR IS DIPPING SOUTH IN THE WAKE
OF THE PREVIOUS SYSTEM AND THE DRY AIR IS FAIRLY DEEP...EXTENDING UP
TO AT LEAST 800 MB. THE INITIAL 2 TO 3 HOURS OF FORCING LIKELY WILL
BE SPENT SATURATING THE COLUMN OVER THE SOUTHWEST AND THE DRY AIR
MAY NOT BE OVERCOME AT ALL OVER THE NORTHEAST. SECOND...THIS SYSTEM
WILL NEED TO RELY ON PACIFIC MOISTURE THAT IS TAGGING ALONG WITH THE
GULF BEING CUT OFF FROM THE PREVIOUS SYSTEM AND THIS WILL FURTHER
COMPLICATE TIMELINESS OF SATURATION. THIRD...THE MAJORITY OF THE
FORCING IS IN THE -20C TO -30C REGION WHICH SUGGESTS PLATES AND
COLUMNS AS THE PRIMARY SNOW CRYSTAL. FINALLY...THE PRIMARY QG
FORCING REMAINS TO THE WEST AND ACROSS EASTERN NEBRASKA. WITH THE
ABOVE SAID...EVENT SHOULD BE SUB ADVISORY CRITERIA FOR MUCH OF THE
AREA WITH MAINLY 1 TO 3 INCHES OVER SOUTHWEST HALF AND AN INCH OR
LESS NORTHEAST.
THE SNOW WILL END EARLY SATURDAY OVER THE SOUTH THEN EXPECT A COOL
AND DRY REMAINDER OF THE WEEKEND. ARCTIC AIR IS JUST OFF TO THE
NORTH AND WILL AFFECT TEMPERATURES ESPECIALLY OVER THE NORTH WHERE
HIGHS WILL STRUGGLE TO GET ABOVE 20 BOTH DAYS. HIGH PRESSURE WILL
SHIFT EAST OF THE AREA BY MONDAY WITH RETURN FLOW DEVELOPING. HIGHS
IN THE 30S AND 40S WILL BE COMMON FOR THE EARLY PORTION OF THE WEEK.
&&
.AVIATION...27/06Z
MUCH OF THE FREEZING PRECIPITATION HAS ENDED...WITH SCATTERED
FLURRIES STILL IMPACTING SOME OF THE TAF SITES. A FEW MVFR VSBYS
REPORTED ACROSS NORTHERN IOWA WITH THE LIGHT SNOW/FLURRIES SO HAVE
SOME TEMPO GROUPS TO COVER THAT. OTHERWISE IFR/MVFR CIGS TO
GRADUALLY LIFT TO MVFR/VFR BY FRIDAY MORNING. ANOTHER SYSTEM TO DROP
THROUGH THE AREA FRIDAY NIGHT BRINGING LOW CLOUDS AND LIGHT SNOW TO
MAINLY THE WESTERN TAF SITES AT KFOD AND KDSM. STRONG AND GUSTY
NORTH WINDS...TO SHIFT MORE TO THE NORTHEAST FRIDAY AND DIMINISH BY
THROUGHOUT THE DAY FRIDAY.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/AVIATION...LEE/MJA
LONG TERM...DONAVON
000
FXUS63 KDVN 270905
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 AM CST FRI FEB 27 2009
.SYNOPSIS...
HIGH PRESSURE WILL QUICKLY MOVE ACROSS THE AREA TODAY BRINGING QUIET
BUT COLDER CONDITIONS TO THE AREA. TONIGHT INTO SATURDAY AN UPPER
LEVEL DISTURBANCE WILL MOVE THROUGH THE REGION BRINGING SOME SNOW TO
THE AREA. AFTER THIS DISTURBANCE EXITS THE AREA SATURDAY EVENING...
AN EXTENDED PERIOD OF QUIET WEATHER IS EXPECTED ACROSS THE MIDWEST.
LATE NEXT WEEK THERE ARE INDICATIONS THAT ANOTHER STORM SYSTEM WILL
AFFECT THE MIDWEST.
&&
.SHORT TERM...TODAY AND TONIGHT...
STORM SYSTEM EXITING THE AREA WITH A DECAYING DEFORMATION ZONE
MOVING ACROSS THE CWFA. RADAR RETURNS/SFC OBS INDICATE WHAT IS
PROBABLY FLURRIES. MODELS ARE NOT HANDLING THE LOW LEVEL MOISTURE
WELL AT ALL BUT INTERNAL SIGNALS INDICATE MOST PRECIP SHOULD BE DONE
BY 12Z. VARIOUS TOOLS SUGGEST THERE MIGHT BE SOME ISOLD FLURRIES
EAST OF THE MISSISSIPPI THROUGH 14Z. AS FOR THE CLOUDS...WILL GO
WITH THE IDEA OF A SLOW CLEARING DURING THE MORNING WITH SOME
SUNSHINE IN THE AFTERNOON. CONFIDENCE ON THIS IS NOT HIGH.
TEMPERATURES TO BE TRICKY AS THE LOW CLOUDS ARE HELPING TO KEEP
OVERNIGHT TEMPERATURES UP. SO...MAX TEMPERATURES FOR TODAY MAY NEED
TO BE ADJUSTED UPWARD.
TONIGHT...THE BETTER FORCING AND LOWER CONDENSATION PRESSURE
DEFICITS REMAIN WEST OF THE CWFA THROUGH 06Z. AFTER 06Z...
CONDENSATION PRESSURE DEFICITS DO LOWER BUT THE FORCING IS NOT
OVERLY GREAT. SO...WILL CONTINUE WITH POPS BUT PLACE THEM WHERE THE
LOWER CONDENSATION PRESSURE DEFICITS AND BETTER LOW LEVEL
CONVERGENCE IS LOCATED. SNOWFALL AMOUNTS SHOULD BE AN INCH OR
LESS. ...08...
.LONG TERM...SATURDAY THROUGH NEXT THURSDAY...
...DRY CONDITIONS THROUGH TUESDAY WITH WARMING TREND NEXT WEEK...
INITIALIZATION GOOD WITH VERIFICATION AT 06Z SUGGESTING BLEND OF GFS
AND HI-RES ECMWF WITH GOOD CONSISTENCY. QUIET NORTHWEST FLOW TO
TRANSITION TO ZONAL FLOW WITH SIGNIFICANT WEST COAST TROUGH BY MID
WEEK.
SATURDAY...TRIMMED POPS AS FORCING FROM UPPER LOW IN PACIFIC
NORTHWEST TO PASS MOSTLY TO SOUTH OF FORECAST REGION. DURING MORNING
ENOUGH MOISTURE AVAILABLE FOR SCATTERED FLURRIES SOUTH OF I-80
SUGGESTED. AT 850/700 MB LEVELS...ENOUGH CONVERGENCE FOR POSSIBLY
SOME LIGHT SNOW ALONG IA/MO BORDER AND HAVE 30-40 POPS WITH DUSTING
TO FEW TENTHS OF AN INCH OF SNOW FOR NE MISSOURI COUNTIES. LATE
FEBRUARY SUNSHINE AND CLEARING SKIES SUPPORT LARGE DIURNAL TRENDS FOR
HIGHS TO REACH NEAR FREEZING MOST LOCATIONS...STILL 10 DEGREES BELOW
NORMAL.
SATURDAY NIGHT THROUGH TUESDAY NIGHT...MOSTLY CLEAR SKIES WITH
CANADIAN HIGH PRESSURE TO SUPPORT COLD NIGHTS AND LARGE DIURNAL
RANGES INTO MONDAY. MINS INTO MONDAY MORNING MAY NEED TRIMMING
ANOTHER FEW MORE DEGREES WITH LIGHT WINDS AND CLEAR SKIES SUPPORTING
MAX RADIATIONAL COOLING CONDITIONS. HIGHS MONDAY AND ESPECIALLY
TUESDAY AS HIGH PRESSURE MOVES EAST. LOW LEVEL THERMAL FIELDS AND
EARLY MARCH SUN SUPPORTS WARMING MAY BE STRONGER FOR LATER SHIFTS TO
CONSIDER BUMPING TEMPERATURES BY UP TO 5 DEGREES ON TUESDAY.
WEDNESDAY AND THURSDAY...NO CHANGES MADE WITH PACIFIC ENERGY TO
APPROACH CENTRAL US SUGGESTING CHANCE POPS OF RAIN WITH ABOVE NORMAL
TEMPERATURES. MAGNITUDE OF THIS SYSTEM SHOULD BE CLARIFIED NEXT 36-
48 HOURS. LIGHT TO MODERATE PRECIPITATION AMOUNTS SUGGESTED ATTM
BASED ON MODEST UPPER JET STREAK VELOCITY STRUCTURES. ..NICHOLS..
&&
.AVIATION...
CONDITIONS SLOWLY IMPROVING WITH MOST CIGS AROUND 1KFT. CIGS TO HOLD
IN THE 1-2KFT RANGE TO AROUND 18Z WHEN THE LOW LEVEL CLOUDS SHOULD
BREAK UP WITH VFR CONDITIONS IN THE AFTERNOON AND EVENING. SOME
ISOLD --SN MAY BE SEEN UNTIL 14Z FROM THE MISSISSIPPI RIVER ON EAST.
UPPER LEVEL DISTURBANCE ARRIVES LATE TONIGHT. FORCING IS NOT GREAT
BUT THERE SHOULD BE SOME -SN. BEST GUESS RIGHT NOW IS CIGS DROPPING
TO AROUND 1KFT AT KBRL WITH 3-5SM. KCID/KMLI/KDBQ TO BE AFFECTED
LESS BUT SHOULD SEE CIGS OF 2-3KFT. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
000
FXUS63 KDMX 270548
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1150 PM CST THU FEB 26 2009
.UPDATED FOR THE 06Z AVIATION DISCUSSION...
.FORECAST UPDATE...
MUCH OF THE FREEZING DRIZZLE HAS ENDED...WITH SOME FLURRIES STILL
MOVING THROUGH THE CWA. LOW CLOUDS CONTINUE ALONG WITH STRONG AND
GUSTY NORTHWEST WINDS. UPDATED THE FORECAST TO CLEAN UP THE WORDING
AND ADD IN FLURRIES FOR THE REMAINDER OF THE NIGHT.
.SHORT TERM.../TONIGHT THROUGH SUN NIGHT/
MAIN FORECAST CONCERN IS WINDS AND PRECIP CHANCES DURING THE EVENING
HOURS. SURFACE LOW QUICKLY PUSHING EASTWARD WITH SHORTWAVE LOCATED
OVER THE DAKOTAS AS SEEN ON WATER VAPOR. ONCE SW MOVES THROUGH
BETWEEN 03-06Z FRIDAY...NNW WINDS LOOK TO INCREASE ACROSS CWA. MAY
SEE A FEW FLURRIES WITH CAA TONIGHT AND POTENTIALLY DURING THE
OVERNIGHT HOURS. A WEAK TROWAL SETS UP ON THE BACKSIDE OF THE LOW
AND KEPT IN SNOW CHANCES ACROSS THE NORTHEAST. SHARP GRADIENT WITH
850MB WINDS 30-40KTS WHICH MAY MIX DOWN TO SURFACE THROUGH 12Z
FRIDAY BEFORE DIMINISHING SLIGHTLY.
NEXT SYSTEM OF CONCERN NOW APPROACHING THE BITTERROOTS AND WILL DROP
INTO THE MO VALLEY LATE FRI. MODELS AND ENSEMBLES ARE QUITE SIMILAR
WITH THE TRACK...HOWEVER NAM IS AT LEAST SIX HOURS SLOWER THAN
CONSENSUS SO IT WILL BE IGNORED FOR NOW LEANING HEAVILY TOWARD THE
GFS. AS HAS BEEN CONSISTENT WITH THE PAST FEW SYSTEMS...DENDRITIC
GROWTH ZONE /DGZ/ IS H6/H7 OR 290-300K WITH SNOW MOVING MAINLY
ACROSS SWRN HALF OF IA. GFS COBB SNOW RATIOS ARE WELL INTO THE
TEENS AND EVEN GETTING INTO THE LOWER 20S AT TIMES. THIS SEEMS TO
BE A RESULT OF DGZ DEPTH RATHER THAN ANYTHING ELSE. QG
FORCING...MODEL OMEGA AND MOISTURE TRANSPORT ALL LOOK MODERATE AT
BEST WITH MOISTURE TRANSPORT ESPECIALLY ON THE LOW SIDE. HIGHER
RATIOS MAY BE A RESULT OF DGZ DEPTH INCREASING AS COLD AIR MOVES IN
AND SLIDES ISOTHERMAL LAYER TOWARD -12C. WITH SIX TO NINE HOURS OF
LIGHT-MODERATE SNOW EXPECTED...AN ADVY EVENT SEEMS LIKELY WITH 2-4
INCH ACCUMS ALONG AND SW OF SPW-IFA-OOA LINE. ISOLATED 5 INCH
AMOUNTS POSSIBLY SW. NO REAL DEVIATIONS FROM GUIDANCE FOR
TEMPS...ALTHOUGH DID TRIM A FEW EXTRA DEGREES SW HALF SAT NIGHT AND
SUN DUE TO LIKELY SNOW COVER.
.LONG TERM.../MON THROUGH THU/
THIS PERIOD LOOKS RELATIVELY UNEVENTFUL WITH ONLY CONCERN POSSIBLE
SYSTEM AROUND DAYS SIX OR SEVEN. ERN ROCKIES LONG WAVE RIDGE WILL
KEEP FAIR WEATHER AND SEASONAL TEMPERATURES IN PLACE THROUGH
MIDWEEK. 00Z MODELS WERE MAINLY DRY...HOWEVER 12Z GFS/ECMWF ARE
TRENDING TOWARD PRECIP AS WEAK SHORT WAVES TOP RIDGE IN WARM
ADVECTION REGIME. MAY HAVE TO INTRODUCE POPS A BIT EARLIER IF THESE
TRENDS CONTINUE. MODELS WERE IN FAIRLY GOOD AGREEMENT UP TO THIS
POINT BUT DIVERGE SOMEWHAT BY WED WITH ECMWF MORE AGGRESSIVE
BRINGING SHORT WAVE INTO MO VALLEY. ALTHOUGH SCENARIOS ARE
DIFFERENT...BOTH MODELS SUGGEST PRECIP BY WED/THU SO HAVE ADDED
CHANCES POPS.
&&
.AVIATION...27/06Z
MUCH OF THE FREEZING PRECIPITATION HAS ENDED...WITH SCATTERED
FLURRIES STILL IMPACTING SOME OF THE TAF SITES. A FEW MVFR VSBYS
REPORTED ACROSS NORTHERN IOWA WITH THE LIGHT SNOW/FLURRIES SO HAVE
SOME TEMPO GROUPS TO COVER THAT. OTHERWISE IFR/MVFR CIGS TO
GRADUALLY LIFT TO MVFR/VFR BY FRIDAY MORNING. ANOTHER SYSTEM TO DROP
THROUGH THE AREA FRIDAY NIGHT BRINGING LOW CLOUDS AND LIGHT SNOW TO
MAINLY THE WESTERN TAF SITES AT KFOD AND KDSM. STRONG AND GUSTY
NORTH WINDS...TO SHIFT MORE TO THE NORTHEAST FRIDAY AND DIMINISH BY
THROUGHOUT THE DAY FRIDAY.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
KLP/BSS/MJA
000
FXUS63 KDMX 262340
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
540 PM CST THU FEB 26 2009
.UPDATED FOR THE 00Z AVIATION DISCUSSION...
.SHORT TERM.../TONIGHT THROUGH SUN NIGHT/
MAIN FORECAST CONCERN IS WINDS AND PRECIP CHANCES DURING THE EVENING
HOURS. SURFACE LOW QUICKLY PUSHING EASTWARD WITH SHORTWAVE LOCATED
OVER THE DAKOTAS AS SEEN ON WATER VAPOR. ONCE SW MOVES THROUGH
BETWEEN 03-06Z FRIDAY...NNW WINDS LOOK TO INCREASE ACROSS CWA. MAY
SEE A FEW FLURRIES WITH CAA TONIGHT AND POTENTIALLY DURING THE
OVERNIGHT HOURS. A WEAK TROWAL SETS UP ON THE BACKSIDE OF THE LOW
AND KEPT IN SNOW CHANCES ACROSS THE NORTHEAST. SHARP GRADIENT WITH
850MB WINDS 30-40KTS WHICH MAY MIX DOWN TO SURFACE THROUGH 12Z
FRIDAY BEFORE DIMINISHING SLIGHTLY.
NEXT SYSTEM OF CONCERN NOW APPROACHING THE BITTERROOTS AND WILL DROP
INTO THE MO VALLEY LATE FRI. MODELS AND ENSEMBLES ARE QUITE SIMILAR
WITH THE TRACK...HOWEVER NAM IS AT LEAST SIX HOURS SLOWER THAN
CONSENSUS SO IT WILL BE IGNORED FOR NOW LEANING HEAVILY TOWARD THE
GFS. AS HAS BEEN CONSISTENT WITH THE PAST FEW SYSTEMS...DENDRITIC
GROWTH ZONE /DGZ/ IS H6/H7 OR 290-300K WITH SNOW MOVING MAINLY
ACROSS SWRN HALF OF IA. GFS COBB SNOW RATIOS ARE WELL INTO THE
TEENS AND EVEN GETTING INTO THE LOWER 20S AT TIMES. THIS SEEMS TO
BE A RESULT OF DGZ DEPTH RATHER THAN ANYTHING ELSE. QG
FORCING...MODEL OMEGA AND MOISTURE TRANSPORT ALL LOOK MODERATE AT
BEST WITH MOISTURE TRANSPORT ESPECIALLY ON THE LOW SIDE. HIGHER
RATIOS MAY BE A RESULT OF DGZ DEPTH INCREASING AS COLD AIR MOVES IN
AND SLIDES ISOTHERMAL LAYER TOWARD -12C. WITH SIX TO NINE HOURS OF
LIGHT-MODERATE SNOW EXPECTED...AN ADVY EVENT SEEMS LIKELY WITH 2-4
INCH ACCUMS ALONG AND SW OF SPW-IFA-OOA LINE. ISOLATED 5 INCH
AMOUNTS POSSIBLY SW. NO REAL DEVIATIONS FROM GUIDANCE FOR
TEMPS...ALTHOUGH DID TRIM A FEW EXTRA DEGREES SW HALF SAT NIGHT AND
SUN DUE TO LIKELY SNOW COVER.
.LONG TERM.../MON THROUGH THU/
THIS PERIOD LOOKS RELATIVELY UNEVENTFUL WITH ONLY CONCERN POSSIBLE
SYSTEM AROUND DAYS SIX OR SEVEN. ERN ROCKIES LONG WAVE RIDGE WILL
KEEP FAIR WEATHER AND SEASONAL TEMPERATURES IN PLACE THROUGH
MIDWEEK. 00Z MODELS WERE MAINLY DRY...HOWEVER 12Z GFS/ECMWF ARE
TRENDING TOWARD PRECIP AS WEAK SHORT WAVES TOP RIDGE IN WARM
ADVECTION REGIME. MAY HAVE TO INTRODUCE POPS A BIT EARLIER IF THESE
TRENDS CONTINUE. MODELS WERE IN FAIRLY GOOD AGREEMENT UP TO THIS
POINT BUT DIVERGE SOMEWHAT BY WED WITH ECMWF MORE AGGRESSIVE
BRINGING SHORT WAVE INTO MO VALLEY. ALTHOUGH SCENARIOS ARE
DIFFERENT...BOTH MODELS SUGGEST PRECIP BY WED/THU SO HAVE ADDED
CHANCES POPS.
&&
.AVIATION...27/00Z
PRECIPITATION CONTINUES TO BE AN ISSUE AS AN AREA OF VERY LIGHT
FREEZING DRIZZLE/RAIN CONTINUES TO MOVE ACROSS THE NORTHERN PORTION
OF THE CWA ALONG WITH SOME IFR/LIFR CIGS AND IFR VSBYS. EXPECT
ENOUGH COLD AIR OVER THE NEXT FEW HOURS THAT FZRA SHOULD MIX IN WITH
SLEET AND SNOW...AND TAPER OFF BY LATE EVENING. MAY SEE A BRIEF
PERIOD OF FZDZ OR SN AT KDSM/KOTM BY MID EVENING...BUT MOST OF THE
PRECIP SHOULD STAY CONFINED TO THE NORTHERN HALF OF THE CWA.
OTHERWISE STRONG AND GUSTY NORTHWEST WINDS EXPECTED TO CONTINUE
THROUGH THE NIGHT...WITH CIGS REMAINING INTO THE IFR/MVFR RANGE
THROUGH THE TAF PERIOD.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
KLP/BSS/MJA
000
FXUS63 KDMX 262142
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
341 PM CST THU FEB 26 2009
.SHORT TERM.../TONIGHT THROUGH SUN NIGHT/
MAIN FORECAST CONCERN IS WINDS AND PRECIP CHANCES DURING THE EVENING
HOURS. SURFACE LOW QUICKLY PUSHING EASTWARD WITH SHORTWAVE LOCATED
OVER THE DAKOTAS AS SEEN ON WATER VAPOR. ONCE SW MOVES THROUGH
BETWEEN 03-06Z FRIDAY...NNW WINDS LOOK TO INCREASE ACROSS CWA. MAY
SEE A FEW FLURRIES WITH CAA TONIGHT AND POTENTIALLY DURING THE
OVERNIGHT HOURS. A WEAK TROWAL SETS UP ON THE BACKSIDE OF THE LOW
AND KEPT IN SNOW CHANCES ACROSS THE NORTHEAST. SHARP GRADIENT WITH
850MB WINDS 30-40KTS WHICH MAY MIX DOWN TO SURFACE THROUGH 12Z
FRIDAY BEFORE DIMINISHING SLIGHTLY.
NEXT SYSTEM OF CONCERN NOW APPROACHING THE BITTERROOTS AND WILL DROP
INTO THE MO VALLEY LATE FRI. MODELS AND ENSEMBLES ARE QUITE SIMILAR
WITH THE TRACK...HOWEVER NAM IS AT LEAST SIX HOURS SLOWER THAN
CONSENSUS SO IT WILL BE IGNORED FOR NOW LEANING HEAVILY TOWARD THE
GFS. AS HAS BEEN CONSISTENT WITH THE PAST FEW SYSTEMS...DENDRITIC
GROWTH ZONE /DGZ/ IS H6/H7 OR 290-300K WITH SNOW MOVING MAINLY
ACROSS SWRN HALF OF IA. GFS COBB SNOW RATIOS ARE WELL INTO THE
TEENS AND EVEN GETTING INTO THE LOWER 20S AT TIMES. THIS SEEMS TO
BE A RESULT OF DGZ DEPTH RATHER THAN ANYTHING ELSE. QG
FORCING...MODEL OMEGA AND MOISTURE TRANSPORT ALL LOOK MODERATE AT
BEST WITH MOISTURE TRANSPORT ESPECIALLY ON THE LOW SIDE. HIGHER
RATIOS MAY BE A RESULT OF DGZ DEPTH INCREASING AS COLD AIR MOVES IN
AND SLIDES ISOTHERMAL LAYER TOWARD -12C. WITH SIX TO NINE HOURS OF
LIGHT-MODERATE SNOW EXPECTED...AN ADVY EVENT SEEMS LIKELY WITH 2-4
INCH ACCUMS ALONG AND SW OF SPW-IFA-OOA LINE. ISOLATED 5 INCH
AMOUNTS POSSIBLY SW. NO REAL DEVIATIONS FROM GUIDANCE FOR
TEMPS...ALTHOUGH DID TRIM A FEW EXTRA DEGREES SW HALF SAT NIGHT AND
SUN DUE TO LIKELY SNOW COVER.
.LONG TERM.../MON THROUGH THU/
THIS PERIOD LOOKS RELATIVELY UNEVENTFUL WITH ONLY CONCERN POSSIBLE
SYSTEM AROUND DAYS SIX OR SEVEN. ERN ROCKIES LONG WAVE RIDGE WILL
KEEP FAIR WEATHER AND SEASONAL TEMPERATURES IN PLACE THROUGH
MIDWEEK. 00Z MODELS WERE MAINLY DRY...HOWEVER 12Z GFS/ECMWF ARE
TRENDING TOWARD PRECIP AS WEAK SHORT WAVES TOP RIDGE IN WARM
ADVECTION REGIME. MAY HAVE TO INTRODUCE POPS A BIT EARLIER IF THESE
TRENDS CONTINUE. MODELS WERE IN FAIRLY GOOD AGREEMENT UP TO THIS
POINT BUT DIVERGE SOMEWHAT BY WED WITH ECMWF MORE AGGRESSIVE
BRINGING SHORT WAVE INTO MO VALLEY. ALTHOUGH SCENARIOS ARE
DIFFERENT...BOTH MODELS SUGGEST PRECIP BY WED/THU SO HAVE ADDED
CHANCES POPS.
&&
.AVIATION...26/18Z
FORECAST CONCERNS ARE PRECIP TYPE AND IFR/LIFR CONDITIONS THROUGH
TONIGHT...THEN STRONG WINDS LATE TONIGHT THROUGH FRIDAY MORNING.
MCW...FOD...AND ALO SHOULD SEE A CHANGE OVER TO FZRA AND SLEET
DURING THE FIRST 6 HOURS OF TAF PERIOD. SO EXPECTING A WINTRY COMBO
THROUGH 00Z/01Z TONIGHT FOR THE NORTHERN THREE TAF SITES WITH WARM
AIR ALOFT. WINDS LOOKS TO SWITCH TO NORTH NORTHEAST BY 21Z IN DSM
AND ALO. THUNDERSTORMS ARE POSSIBLE AT DSM AND OTM THROUGH 00Z
FRIDAY. RAIN HAS BEEN QUICK BUT HEAVY. STRONG PRESSURE GRADIENT SETS
UP BEHIND LOW AND HAVE REFLECTED STRONG WINDS IN ALL TAFS THROUGH
FRIDAY MORNING. IFR CIGS AND VIS SHOULD PERSIST THIS AFTERNOON AND
EVENING FOR OTM AND DES.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
KLP/BSS
000
FXUS63 KDVN 262114 CCA
AFDDVN
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
303 PM CST THU FEB 26 2009
.DISCUSSION...
ELEVATED CONVECTION BLOSSOMING AS SYNOPTIC SCALE LIFT RAMPING UP WITH
APPROACH OF LOW AMPLITUDE SHORTWAVE TROUGH AND LEFT FRONT QUAD OF
JET. 20Z MSAS SFC ANALYSIS PLACES LOW BETWEEN KTNU AND KIOW WITH
3 HR PRESSURE FALL BULLSEYE OF 6-7 MBS FAR NORTHEAST IA...NORTHERN IL
AND SOUTHERN WI SUPPORTING E/NE MOVEMENT OF LOW. COLD FRONT TRAILS
BACK THROUGH SOUTH CENTRAL IA AND NORTHWEST MO. PCPN SHUTS DOWN
QUICKLY JUST BEHIND COLD FRONT. REGIONAL RADARS SHOW MAIN DEFORMATION
ZONE WELL NORTH EXTENDING FROM CENTRAL MN INTO THE EASTERN DAKOTAS.
LIFT FROM SHORTWAVE TROUGH AND JET STREAK UNDERCUTTING SYSTEM TO
DIMINISH QUICKLY LATE AFTN INTO EARLY EVE FROM WEST TO EAST WHILE
COLD FRONT PASSES. CWA WILL DODGE BRUNT OF WINTERY SIDE OF SYSTEM
AS PCPN LOOKS TO DIMINISH BEFORE COLD AIR DEEPENS. HOWEVER... FCST
SOUNDINGS SUPPORT IF ANY PCPN POST FRONTAL IT WOULD BE DRIZZLE AND
POSSIBLY FREEZING DRIZZLE DEPENDING ON TEMPS. HAVE NOT SEEN ANY
REPORTS BUT CIGS QUITE LOW WEST AND WOULD NOT BE SURPRISED TO SEE
THUS WILL ADD TO FCST TNGT... MAINLY THIS EVE. OTHER ITEM TO WATCH
IS DEFORMATION ZONE WELL TO OUR NORTH. MODELS SUGGEST THIS MAY BRUSH
NORTH 1/2 LATE EVE INTO THE OVERNIGHT... AND WILL CARRY SOME POPS
FOR THIS.
COLDER/BLUSTERY FOR FRI AS WEAK RIDGING BUILDS IN BEHIND DEPARTING
STORM SYSTEM.
FOCUS THEN QUICKLY TURNS TO NEXT SYSTEM... POTENT CLOSED LOW DIVING
E/SE THROUGH PACIFIC NORTHWEST EARLY THIS AFTN. THIS SYSTEM TO
BE SHUTTLED JUST TO OUR SOUTHWEST FRI NIGHT-SAT AM BRING SNOW TO
SOUTHWEST 1/3-1/2 WHERE VARIOUS METHODS SUPPORT 1-3 INCHES WITH THE
POTENTIAL FOR ISOLD 4 INCH AMOUNTS EXTREME SOUTHWEST CWA. GREAT LAKES
SFC RIDGE TO THEN SETTLE IN FOR LATTER HALF OF WEEKEND WITH DRY WX
AND TEMPS BELOW NORMAL. BEYOND...OVERALL SUGGESTION OF SEMI ZONAL
FLOW DEVELOPING WITH TEMPS MODERATING. ANOTHER SYSTEM APPEARS SLATED
TO ARRIVE BY WED-THURS WITH GULF OPEN FOR POTENTIALLY MODERATE TO
LOCALLY HEAVY PCPN EVENT.
&&
.AVIATION...
IFR..AND AREAS OF LIFR...CONDITIONS DUE TO FOG AND WIDESPREAD SHOWERS
AND THUNDERSTORMS WILL IMPROVE THIS EVENING AS A LOW PRESSURE SYSTEM
SLIDES THROUGH THE REGION. WINDS WILL VEER AROUND TO THE NORTHWEST
AND INCREASE TO 15 TO 25 KTS AT ALL SITES THIS EVENING AS THE SYSTEM
MOVES THROUGH. THERE MAY BE AN HOUR OR TWO OF 20 TO NEAR 30 KT WINDS
FOLLOWING THE SYSTEMS COLD FRONTAL PASSAGE THIS EVENING.
THUNDERSTORMS WILL SWEEP EAST OF THE AREA BY 01Z...POSSIBLY FOLLOWED
BY A PERIOD OF LIGHT MIXED FREEZING PRECIPITATION THIS EVENING...
WHICH HAS BEEN INCLUDED IN THE FORECASTS. THE DRIER AIR WILL LIFT
CIGS INTO MVFR RANGE AT MOST SITES BY MIDNIGHT...WITH MVFR GIVING
WAY TO VFR TOWARD NOON ON FRI. ..SHEETS..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
MCCLURE/SHEETS
000
FXUS63 KDVN 262105
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
303 PM CST THU FEB 26 2009
.DISCUSSION...
ELEVATED CONVECTION BLOSSOMING AS SYNOPTIC SCALE LIFT RAMPING UP WITH
APPROACH OF LOW AMPLITUDE SHORTWAVE TROUGH AND LEFT FRONT QUAD OF
JET. 20Z MSAS SFC ANALYSIS PLACES LOW BETWEEN KTNU AND KIOW WITH
3 HR PRESSURE FALL BULLSEYE OF 6-7 MBS FAR NORTHEAST IA...NORTHERN IL
AND SOUTHERN WI SUPPORTING E/NE MOVEMENT OF LOW. COLD FRONT TRAILS
BACK THROUGH SOUTH CENTRAL IA AND NORTHWEST MO. PCPN SHUTS DOWN
QUICKLY JUST BEHIND COLD FRONT. REGIONAL RADARS SHOW MAIN DEFORMATION
ZONE WELL NORTH EXTENDING FROM CENTRAL MN INTO THE EASTERN DAKOTAS.
LIFT FROM SHORTWAVE TROUGH AND JET STREAK UNDERCUTTING SYSTEM TO
DIMINISH QUICKLY LATE AFTN INTO EARLY EVE FROM WEST TO EAST WHILE
COLD FRONT PASSES. CWA WILL DODGE BRUNT OF WINTERY SIDE OF SYSTEM
AS PCPN LOOKS TO DIMINISH BEFORE COLD AIR DEEPENS. HOWEVER... FCST
SOUNDINGS SUPPORT IF ANY PCPN POST FRONTAL IT WOULD BE DRIZZLE AND
POSSIBLY FREEZING DRIZZLE DEPENDING ON TEMPS. HAVE NOT SEEN ANY
REPORTS BUT CIGS QUITE LOW WEST AND WOULD NOT BE SURPRISED TO SEE
THUS WILL ADD TO FCST TNGT... MAINLY THIS EVE. OTHER ITEM TO WATCH
IS DEFORMATION ZONE WELL TO OUR NORTH...BUT MODELS SUGGEST THIS
WILL STAY NORTH WHICH IS SUPPORTED BY RECENT RADAR TRENDS... THUS WILL
NOT CARRY ANY POPS AFT 06Z. THOUGH MAY SEE SOME LINGERING DZ/FZDZ
WITH POSSIBLY FEW FLURRIES FAR NORTH.
COLDER/BLUSTERY FOR FRI AS WEAK RIDGING BUILDS IN BEHIND DEPARTING
STORM SYSTEM.
FOCUS THEN QUICKLY TURNS TO NEXT SYSTEM... POTENT CLOSED LOW DIVING
E/SE THROUGH PACIFIC NORTHWEST EARLY THIS AFTN. THIS SYSTEM TO
BE SHUTTLED JUST TO OUR SOUTHWEST FRI NIGHT-SAT AM BRING SNOW TO
SOUTHWEST 1/3-1/2 WHERE VARIOUS METHODS SUPPORT 1-3 INCHES WITH THE
POTENTIAL FOR ISOLD 4 INCH AMOUNTS EXTREME SOUTHWEST CWA. GREAT LAKES
SFC RIDGE TO THEN SETTLE IN FOR LATTER HALF OF WEEKEND WITH DRY WX
AND TEMPS BELOW NORMAL. BEYOND...OVERALL SUGGESTION OF SEMI ZONAL
FLOW DEVELOPING WITH TEMPS MODERATING. ANOTHER SYSTEM APPEARS SLATED
TO ARRIVE BY WED-THURS WITH GULF OPEN FOR POTENTIALLY MODERATE TO
LOCALLY HEAVY PCPN EVENT.
&&
.AVIATION...
IFR..AND AREAS OF LIFR...CONDITIONS DUE TO FOG AND WIDESPREAD SHOWERS
AND THUNDERSTORMS WILL IMPROVE THIS EVENING AS A LOW PRESSURE SYSTEM
SLIDES THROUGH THE REGION. WINDS WILL VEER AROUND TO THE NORTHWEST
AND INCREASE TO 15 TO 25 KTS AT ALL SITES THIS EVENING AS THE SYSTEM
MOVES THROUGH. THERE MAY BE AN HOUR OR TWO OF 20 TO NEAR 30 KT WINDS
FOLLOWING THE SYSTEMS COLD FRONTAL PASSAGE THIS EVENING.
THUNDERSTORMS WILL SWEEP EAST OF THE AREA BY 01Z...POSSIBLY FOLLOWED
BY A PERIOD OF LIGHT MIXED FREEZING PRECIPITATION THIS EVENING...
WHICH HAS BEEN INCLUDED IN THE FORECASTS. THE DRIER AIR WILL LIFT
CIGS INTO MVFR RANGE AT MOST SITES BY MIDNIGHT...WITH MVFR GIVING
WAY TO VFR TOWARD NOON ON FRI. ..SHEETS..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
MCCLURE/SHEETS
000
FXUS63 KDMX 261802 AAB
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1200 PM CST THU FEB 26 2009
...UPDATED AVIATION DISCUSSION 26/18Z.
.SHORT TERM...(TODAY)
VERY COMPLEX FORECAST FOR TODAY WITH FREEZING RAIN ACROSS THE
WEST AND NORTH THIS MORNING EVENTUALLY SWITCHING OVER TO SNOW FAR
NORTH THIS AFTERNOON WITH AN EVENTUAL TRANSITION TO A MIX AND THEN
SNOW LATER TODAY. MODIFICATIONS FROM PREVIOUS PACKAGE INCLUDE
ADDING ANOTHER 3 COUNTIES TO THE ADVISORY FROM STORY EAST TO TAMA
COUNTIES...BUMPING UP SNOWFALL TOTALS ACROSS THE FAR NORTH AND
ALSO ADJUSTING THE AMOUNT OF EXPECTED ICE. AT THIS TIME...STILL
LOOKS LIKE BETWEEN .20 AND .30 OVERALL...BUT COMPLICATING THE
MATTER IS THE FACT THAT CONVECTION HAS ALREADY COMMENCED TO OUR
WEST WITH BUFKIT SOUNDINGS SHOWING INSTABILITY FARTHER NORTH INTO
THE COLDER AIR TODAY. THIS WOULD MEAN POSSIBLE THUNDER SLEET OR
THUNDER FREEZING RAIN OVER SOME AREAS THIS MORNING ESPECIALLY.
SO...WILL NEED TO BE KEEPING A CLOSE WATCH TODAY TO MONITOR IF
ANYTHING CHANGES. HAVE ADVISORY NOW BASICALLY ALONG AND NORTH OF
US 30 WITH WARNING AREAS REMAINING THE SAME. COLDER AIR TO FILTER
IN DURING THE AFTERNOON...BULK OF MOISTURE TRANSPORT SHIFTS TO THE
EAST SO EVEN AS CHANGEOVER OCCURS CENTRAL AND SOUTH...BULK OF
EXPECTED QPF TO ALREADY HAVE MOVED AWAY.
.LONG TERM...(TONIGHT-WED)
A STRONG 700 MB DRY PUNCH WILL MOVE OVER IOWA BY THIS EVENING
HOWEVER THE LOW LEVELS WILL REMAIN SATURATED BELOW THE DRY AIR
WITH SOME LIFT NEAR THE FRONTAL BOUNDARY AS IT MOVES SOUTHEAST.
THE DRY AIR ALOFT WILL RESULT IN NO ICE INTRODUCTION WITH ANY
PRECIPITATION ON THE COLD SIDE OF THE BOUNDARY BEING MAINLY LIGHT
FREEZING RAIN OR FREEZING DRIZZLE. THE PRECIPITATION WILL END FROM
WEST TO EAST BY 06Z.
A RELATIVELY COOL DAY IS ON TAP FOR FRIDAY WITH HIGHS ONLY
REACHING INTO THE MID TEENS OVER THE NORTH AS THE COLD AIR OVER
THE NORTHERN PLAINS DIPS SOUTH IN THE WAKE OF TODAYS SYSTEM.
ANOTHER STRONG SHORT WAVE WILL ARRIVE FRIDAY NIGHT AND WILL BRING
A ROUND OF LIGHT SNOW TO THE REGION. AT THIS TIME...SNOW
ACCUMULATIONS OF 1 TO 3 INCHES LOOK POSSIBLE. HIGHER AMOUNTS WOULD
BE POSSIBLE IF THE SYSTEM SLOWS DOWN AS IT PASSES THROUGH THE
STATE...HOWEVER THE GULF WILL BE CLOSED SO THE SYSTEM WILL ONLY
HAVE PACIFIC MOISTURE THAT HAS TAGGED ALONG FOR THE RIDE TO WORK
WITH AND WILL LIMIT OVERALL TOTALS. THE SNOW WILL BE ENDING
SATURDAY MORNING THEN THE REMAINDER OF THE WEEKEND WILL REMAIN
COOL AND DRY. BEYOND THAT A GRADUAL WARMING TREND IS ANTICIPATED
FOR THE BEGINNING OF NEXT WEEK.
.AVIATION...26/18Z
FORECAST CONCERNS ARE PRECIP TYPE AND IFR/LIFR CONDITIONS THROUGH
TONIGHT...THEN STRONG WINDS LATE TONIGHT THROUGH FRIDAY MORNING.
MCW...FOD...AND ALO SHOULD SEE A CHANGE OVER TO FZRA AND SLEET
DURING THE FIRST 6 HOURS OF TAF PERIOD. SO EXPECTING A WINTRY COMBO
THROUGH 00Z/01Z TONIGHT FOR THE NORTHERN THREE TAF SITES WITH WARM
AIR ALOFT. WINDS LOOKS TO SWITCH TO NORTH NORTHEAST BY 21Z IN DSM
AND ALO. THUNDERSTORMS ARE POSSIBLE AT DSM AND OTM THROUGH 00Z
FRIDAY. RAIN HAS BEEN QUICK BUT HEAVY. STRONG PRESSURE GRADIENT SETS
UP BEHIND LOW AND HAVE REFELCTED STRONG WINDS IN ALL TAFS THROUGH
FRIDAY MORNING. IFR CIGS AND VIS SHOULD PERSIST THIS AFTERNOON AND
EVENING FOR OTM AND DES.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR CERRO GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-
WINNEBAGO-WORTH.
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-FRANKLIN-
GREENE-GRUNDY-HAMILTON-HARDIN-HUMBOLDT-MARSHALL-POCAHONTAS-STORY-
TAMA-WEBSTER-WRIGHT.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
CARROLL-CRAWFORD-SAC.
&&
$$
SHORT TERM...REV
AVIATION...KLP
LONG TERM...DONAVON
000
FXUS63 KDVN 261644
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1044 AM CST THU FEB 26 2009
.UPDATE...
WIDESPREAD DENSE FOG HAS OVERSPREAD THE SOUTHERN THIRD OF THE CWFA
IN THE LOW LEVEL CONVERGENCE AHEAD OF THE WARM FRONT. AT
15Z...SURFACE ANALYSIS INDICATED THIS FRONT REACHING FROM THE
DEVELOPING LOW NEAR KICT ACROSS NRN MO TO NEAR KUIN. SCATTERED
SHOWERS AND THUNDERSTORMS WHERE OCCURRING IN THE ELEVATED WARM
AIR ADVECTION AND H8 SPEED CONVERGENCE ALONG AND WELL NORTH OF
THIS BOUNDARY THIS MORNING. STORMS ROOTED CLOSER TO THE BOUNDARY
HAVE PRODUCED PRIMARILY SMALL HAIL ACCORDING TO UPSTREAM STORM
REPORTS. ELEVATED CORES BEGINNING TO STRENGTHEN OVER DVN CWFA IN
THE SOUTH...WHILE IN THE NORTH SOME ENHANCED REFLECTIVITY LIKELY
INDICATING SLEET ALONG HWY 20 CORRIDOR INCLUDING DBQ AREA.
DENSE FOG WILL LIKELY CONTINUE TO EXPAND W AND N THIS MORNING AS
THE FRONT APPROACHES AND WITH WIDESPREAD 1/4SM VISIBILITIES...HAVE
ISSUED AN ADVISORY. THE FAR SOUTH SHOULD SEE RAPID IMPROVEMENT
ONCE THE BOUNDARY PUSHES THROUGH. SPC HAS EXPANDED THE SLIGHT RISK
NORTH TO I-80 CORRIDOR AND WILL HAVE TO MONITOR APPROACHING STORMS
IN THIS AREA THIS AFTERNOON FOR PRIMARY THREAT OF 1 INCH HAIL. HAVE
UPDATED THE HAZARDOUS WEATHER OUTLOOK TO HIGHLIGHT THIS THREAT.
&&
.AVIATION...
WIDESPREAD IFR CONDITIONS WILL PREVAIL TODAY DUE TO FOG AND LOW
CIGS. DENSE FOG WILL KEEP CONDITIONS IN LIFR AT BRL THROUGH
NOON...AND POSSIBLY IMPACT MLI AND CID THROUGH EARLY AFTERNOON.
ISOLATED SHOWERS AND THUNDERSTORMS WILL BECOME MORE NUMEROUS THIS
AFTERNOON. WITH LOW PROBABILITY OF IMPACTING FORECAST SITES...WILL
CONTINUE TO HANDLE THUNDERSTORM THREAT WITH CB MENTION AND VCTS.
WINTER STORM SYSTEM WILL SWEEP A COLD FRONT THROUGH TONIGHT...
CHANGING PRECIPITATION THREAT FROM RAIN TO POSSIBLY SOME FREEZING
PRECIPITATION BEFORE CHANGEOVER TO SNOW LATE TONIGHT. WITH THE
FRONTAL PASSAGE...DRIER AIR WILL IMPROVE CIGS AND VISBYS WELL INTO
MVFR CRITERIA FRI MORNING. THIS WILL ALSO BRING A WIND SHIFT TO NW
WITH SPEEDS OF 15 TO 25 KTS.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...DENSE FOG ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR DES MOINES-
HENRY IA-JEFFERSON-LOUISA-MUSCATINE-SCOTT-WASHINGTON.
DENSE FOG ADVISORY UNTIL 1 PM CST THIS AFTERNOON FOR LEE-VAN
BUREN.
IL...DENSE FOG ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR BUREAU-
HENDERSON-HENRY IL-MERCER-PUTNAM-ROCK ISLAND-WARREN-
WHITESIDE.
DENSE FOG ADVISORY UNTIL 1 PM CST THIS AFTERNOON FOR HANCOCK-
MCDONOUGH.
MO...DENSE FOG ADVISORY UNTIL 1 PM CST THIS AFTERNOON FOR CLARK-
SCOTLAND.
&&
$$
SHEETS
000
FXUS63 KDMX 261121 AAA
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
522 AM CST THU FEB 26 2009
.AVIATION DISCUSSION 26/12Z.
.SHORT TERM...(TODAY)
VERY COMPLEX FORECAST FOR TODAY WITH FREEZING RAIN ACROSS THE
WEST AND NORTH THIS MORNING EVENTUALLY SWITCHING OVER TO SNOW FAR
NORTH THIS AFTERNOON WITH AN EVENTUAL TRANSITION TO A MIX AND THEN
SNOW LATER TODAY. MODIFICATIONS FROM PREVIOUS PACKAGE INCLUDE
ADDING ANOTHER 3 COUNTIES TO THE ADVISORY FROM STORY EAST TO TAMA
COUNTIES...BUMPING UP SNOWFALL TOTALS ACROSS THE FAR NORTH AND
ALSO ADJUSTING THE AMOUNT OF EXPECTED ICE. AT THIS TIME...STILL
LOOKS LIKE BETWEEN .20 AND .30 OVERALL...BUT COMPLICATING THE
MATTER IS THE FACT THAT CONVECTION HAS ALREADY COMMENCED TO OUR
WEST WITH BUFKIT SOUNDINGS SHOWING INSTABILITY FARTHER NORTH INTO
THE COLDER AIR TODAY. THIS WOULD MEAN POSSIBLE THUNDER SLEET OR
THUNDER FREEZING RAIN OVER SOME AREAS THIS MORNING ESPECIALLY.
SO...WILL NEED TO BE KEEPING A CLOSE WATCH TODAY TO MONITOR IF
ANYTHING CHANGES. HAVE ADVISORY NOW BASICALLY ALONG AND NORTH OF
US 30 WITH WARNING AREAS REMAINING THE SAME. COLDER AIR TO FILTER
IN DURING THE AFTERNOON...BULK OF MOISTURE TRANSPORT SHIFTS TO THE
EAST SO EVEN AS CHANGEOVER OCCURS CENTRAL AND SOUTH...BULK OF
EXPECTED QPF TO ALREADY HAVE MOVED AWAY.
.LONG TERM...(TONIGHT-WED)
A STRONG 700 MB DRY PUNCH WILL MOVE OVER IOWA BY THIS EVENING
HOWEVER THE LOW LEVELS WILL REMAIN SATURATED BELOW THE DRY AIR
WITH SOME LIFT NEAR THE FRONTAL BOUNDARY AS IT MOVES SOUTHEAST.
THE DRY AIR ALOFT WILL RESULT IN NO ICE INTRODUCTION WITH ANY
PRECIPITATION ON THE COLD SIDE OF THE BOUNDARY BEING MAINLY LIGHT
FREEZING RAIN OR FREEZING DRIZZLE. THE PRECIPITATION WILL END FROM
WEST TO EAST BY 06Z.
A RELATIVELY COOL DAY IS ON TAP FOR FRIDAY WITH HIGHS ONLY
REACHING INTO THE MID TEENS OVER THE NORTH AS THE COLD AIR OVER
THE NORTHERN PLAINS DIPS SOUTH IN THE WAKE OF TODAYS SYSTEM.
ANOTHER STRONG SHORT WAVE WILL ARRIVE FRIDAY NIGHT AND WILL BRING
A ROUND OF LIGHT SNOW TO THE REGION. AT THIS TIME...SNOW
ACCUMULATIONS OF 1 TO 3 INCHES LOOK POSSIBLE. HIGHER AMOUNTS WOULD
BE POSSIBLE IF THE SYSTEM SLOWS DOWN AS IT PASSES THROUGH THE
STATE...HOWEVER THE GULF WILL BE CLOSED SO THE SYSTEM WILL ONLY
HAVE PACIFIC MOISTURE THAT HAS TAGGED ALONG FOR THE RIDE TO WORK
WITH AND WILL LIMIT OVERALL TOTALS. THE SNOW WILL BE ENDING
SATURDAY MORNING THEN THE REMAINDER OF THE WEEKEND WILL REMAIN
COOL AND DRY. BEYOND THAT A GRADUAL WARMING TREND IS ANTICIPATED
FOR THE BEGINNING OF NEXT WEEK.
.AVIATION...26/12Z
FORECAST CURRENTLY LOOKS ON TRACK...THOUGH NOT VERY AVIATION
FRIENDLY. HAVE STRONG WARM AIR MOVING INTO REGION ALOFT AND AREAS OF
CONVECTION ALREADY FIRING WEST...WITH SLEET AND FREEZING RAIN
POSSIBLE WITH CONVECTION AS THIS AREA MOVES EAST. WILL SEE PSBL
THUNDER/CB NEAR KFOD ~15Z WITH KALO LATER IN THE MORNING. NORTH TAF
SITES SUBJECT TO ZR AND LATER SN/PL. KDSM AND KOTM MAINLY RAIN AND
POSSIBLE THUNDER BEFORE CHANGEOVER LATE AFTERNOON OR EARLY THE 27TH
TO A COMBINATION OF FZRA/-PL/-SN. CIGS COME DOWN TO IFR AFT 15Z.
KMCW MAY SEE BRIEF PERIOD OF 1/2 SN SHORTLY AFT 18Z LASTING A FEW
HOURS. SYSTEM TO PULL OUT EARLY THIS EVENING WITH RESIDUAL FZDZ OR
-SN COMBINED WITH NORTH WINDS TO 24KT AND GUSTS TO ~25 TO 35 KTS AFT
00Z DIMINISHING SOMEWHAT OVERNIGHT./REV
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR CERRO GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-
WINNEBAGO-WORTH.
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-FRANKLIN-
GREENE-GRUNDY-HAMILTON-HARDIN-HUMBOLDT-MARSHALL-POCAHONTAS-STORY-
TAMA-WEBSTER-WRIGHT.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
CARROLL-CRAWFORD-SAC.
&&
$$
SHORT TERM...REV
AVIATION...REV
LONG TERM...DONAVON
000
FXUS63 KDVN 260942
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 AM CST THU FEB 26 2009
.SYNOPSIS...
VERY INTERESTING DEVELOPING WEATHER ACROSS THE MIDWEST THIS MORNING.
THERE IS FINALLY A STRENGTHENING SURFACE LOW BEGINNING TO COME OUT
OF EASTERN COLORADO...WITH A WARM FRONT BOUNDARY EXTENDING FROM IT
EAST ACROSS KANSAS AND NORTHERN MISSOURI TO CENTRAL ILLINOIS.
ALOFT...ON SATELLITE IMAGERY THERE IS AN IMPRESSIVE SHORTWAVE MOVING
ACROSS THE DAKOTAS...ASSOCIATED WITH A 500MB SHORTWAVE. AT 850MB
THERE IS A VERY NICE...BUT SOMEWHAT DIFFUSE AS OF 00Z BAROCLINIC
ZONE EXTENDING FROM SOUTH DAKOTA WITH THE SHORTWAVE EAST-SOUTHEAST
ACROSS IOWA AND INTO NORTHERN ILLINOIS. THESE FEATURES ARE GOING TO
BE THE MAIN FEATURES TO WATCH IN THE NEXT 24 HOURS AS THEY TRANSLATE
ACROSS THE FORECAST AREA.
&&
.SHORT TERM...TODAY AND TONIGHT...
VERY COMPLICATED FORECAST THIS MORNING...WITH PRECIPITATION
BEGINNING TO DEVELOP VERY CLOSE TO WHERE THE MODELS INDICATE THE
925MB BOUNDARY IS. SO FAR THIS ACTIVITY IS VERY SCATTERED IN
NATURE...BUT THIS SHOULD INTENSIFY AND FILL IN DURING THE NEXT 6
HOURS AS THE UPPER LEVEL SHORT WAVE MOVES TOWARDS THE AREA...AND IT
SHOULD ALSO SLOWLY SHIFT NORTH AS THIS BOUNDARY ALSO RESPONDS TO THE
APPROACH OF THE SHORTWAVE AND MOVES NORTH. THE SURFACE LOW WILL
RIPPLE NORTHEAST ALONG THE SURFACE BOUNDARY...LIFTING IT NORTHEAST
AND IT SHOULD MOVE THROUGH THE SOUTHEAST CORNER OF THE FORECAST AREA
AND INTO NORTHERN ILLINOIS BY THIS EVENING. MODELS HAVE FINALLY
COME INTO VERY CLOSE AGREEMENT ON THIS...AND HAVE RATHER HIGH
CONFIDENCE. WHAT IS STILL IN QUESTION IS THE PRECIPITATION TYPE
THIS MORNING...AND WHERE THE HEAVY PRECIPITATION BAND WILL BE. THIS
MORNING THE MAIN QUESTION IS WHETHER THE PRECIPITATION WILL MOVE IN
BEFORE THE TEMPERATURES WARM UP OUT OF THE EARLY MORNING MINS.
CURRENTLY TEMPERATURES ARE DOWN VERY CLOSE TO FREEZING...AND IF
PRECIPITATION WAS ONGOING NOW WE WOULD BE HAVING ICING OCCURRING
OVER THE NORTHERN HALF OF THE FORECAST AREA. HOWEVER...AS THE WARM
FRONT PUSHES NORTH TEMPERATURES WILL RISE...AND AM RATHER CONFIDENT
THAT AFTER 15Z THIS MORNING...ALL RISK OF FREEZING RAIN WILL HAVE
SHIFTED NORTH OF THE FORECAST AREA. SINCE I DO NOT THINK THAT WE
WILL HAVE MORE THAN SCATTERED FREEZING RAIN SHOWERS FOR A VERY BRIEF
PERIOD THIS MORNING...HAVE DECIDED TO HANDLE THIS WITH SPECIAL
WEATHER STATEMENTS RATHER THAN AN ACTUAL ADVISORY. ALSO TODAY...WE
WILL HAVE THUNDER CHANCES FOR THE ENTIRE CWA...THOUGH THE NORTHERN
THIRD OR SO MAY ONLY EXPERIENCE RAIN WITH EMBEDDED THUNDER...AND AS
YOU GET SOUTH WE MAY SEE MORE DISCRETE CONVECTIVE CELLS. IN
FACT...WE ARE IN A SLIGHT RISK OF SEVERE STORMS IN THE FAR
SOUTHEASTERN COUNTIES...LIKELY DUE TO THE VERY LOW FREEZING LEVEL
AND STEEP MID LEVEL LAPSE RATES INDICATING A LARGE HAIL THREAT.
TONIGHT WE BEGIN TO GET BACK INTO PRECIPITATION TYPE CONCERNS AS THE
CONVECTIVE PRECIPITATION SHIFTS EAST...THE COLD AIR DUMPS BACK INTO
HERE FROM THE NORTHWEST. AT THIS TIME THE MODELS ARE TRYING TO
UNDERCUT THE WARM AIR WITH COLD...CREATING A THREAT FOR FREEZING
RAIN THIS EVENING BEFORE THE PRECIPITATION SWITCHES OVER TO ALL SNOW.
AM NOT TOTALLY CONVINCED OF THIS LIKELIHOOD...AND HAVE MENTIONED A
RAIN OR FREEZING RAIN THREAT ONLY IN THE NORTHWEST THIS EVENING.
THIS CONCERN WILL NEED TO BE RE-EVALUATED LATER TODAY AS MORE DATA
COMES IN. OTHERWISE...I HAVE ALL SNOW MENTIONED AFTER MIDNIGHT. AS
THE BEST LIFT MOVES OFF RAPIDLY TO THE EAST AFTER MIDNIGHT...AND WE
LOSE THE MID LEVEL MOISTURE...AM CONCERNED THAT WE MAY SEE ONLY SOME
FREEZING DRIZZLE AFTER MIDNIGHT...BUT AM HOPING THAT THE MOISTURE
WILL BE DEEP ENOUGH FOR SNOW INSTEAD. EITHER WAY...SNOW AMOUNTS
WILL BE QUITE LOW...LIKELY NO MORE THAN A QUARTER INCH. THE MAIN
DEFORMATION ZONE WILL BE OFF TO OUR NORTHEAST. ..LE..
.LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY...
EXPECT A TEMPORARY BOUT OF RIDGING IN THE WAKE OF DEPARTING
EASTERN GRT LKS STORMS SYSTEM FRI...WITH THE EXTENT OF LLVL CAA
SUPPORTING THE COOLER HIGHS ADVERTISED BY THE MAV EXCEPT IN THE
FAR SOUTHEASTERN CWA. THEN ATTENTION TURNS TO THE NEXT WAVE OF
CONSEQUENCE...A RATHER VIGOROUS ONE SEEN CURRENTLY ON W/V IMAGERY
SWIRLING ITS WAY ONTO THE WA COAST. THIS FEATURE IS PROGGED TO GET
SWEPT UP IN BROAD WEST-NORTHWEST SPLIT FLOW PATTERN ACRS THE CONUS
AND GET SHUNTED DOWN RIGHT OVER THE DVN CWA BY MIDDAY SAT...OR DIG
OFF TO THE SOUTHWEST. FORCING AND SATURATION PROGS BY BOTH THE 00Z
RUN NAM AND GFS SUGGEST THAT 1-3 INCHES OF SNOW COULD GET WRUNG OUT
BY THIS FEATURE ACRS THE SOUTHWEST THIRD TO HALF OF THE DVN CWA
FROM 06Z-18Z SAT...TAKING INTO ACCOUNT 15:1 SLR/S. GARCIA METHOD
USING THE 290K SFC ALSO SUPPORTS THESE KIND OF LIGHT SNOW AMOUNTS.
THE NEW 00Z ECMWF DIGS THE WAVE FURTHER TO THE SOUTHWEST AND ONLY
CLIPS THE FAR SOUTHWEST 2-5 COUNTIES OF THE CWA WITH AN INCH OR SO
SAT MORNING. THE WAVE LOOKS TO BE A STRONG ONE ON THE W/V IMAGERY...
BUT THE QUESTION IS IF THERE IS ENOUGH MOISTURE FOR IT TO WORK WITH
TO PRODUCE MORE SNOW THAN CURRENTLY EXPECTED IN THE NW FLOW PATTERN.
FOR NOW...WILL UP THE CHC POPS IN THE WEST AND SOUTHWEST AFTER 06Z
SAT THROUGH 12Z SAT...AND LOW TO MODERATE CHC POPS CWA-WIDE FOR SAT.
REINFORCING SFC RIDGE WILL THEN LOOK TO SLIDE DOWN ACRS THE UPPER
MIDWEST AND WESTERN GRT LKS SAT NIGHT INTO SUNDAY FOR A FAIR BUT COOL
WX REGIME TO ROUND OUT THE WEEKEND. SINGLE DIGIT LOW TEMPS POSSIBLE
AGAIN FOR THE NORTHERN CWA SAT NIGHT...AND MUCH MORE OF THE CWA
ESPECIALLY WITH ANY KIND OF NEW LIGHT SNOW COVER SUNDAY NIGHT WITH
RIDGE AXIS ALMOST OVERHEAD. RETURN FLOW STILL ON TARGET TO BRING
THERMAL MODERATION PROBABLY BACK INTO THE 40S FOR EARLY NEXT WEEK.
..12..
&&
.AVIATION...
CURRENT VFR CIGS WITH MVFR VSBYS WILL SLOWLY DETERIORATE THIS
MORNING...SO THAT BY MID-DAY THE TAF LOCATIONS WILL SEE IFR CIGS AND
VSBYS IN RAIN AND THUNDERSTORMS. STRONGEST STORMS WILL PRODUCE LIFR
CONDITIONS. A BRIEF PERIOD OF FREEZING RAIN IS POSSIBLE THIS MORNING
AT KDBQ AND KCID BEFORE TEMPS WARM AND IT TURNS TO ALL RAIN. TONIGHT
THE THREAT OF ICING RETURNS AS COLD AIR MOVES IN...BUT SHOULD BE ALL
SNOW AROUND MIDNIGHT...STILL IN IFR CONDITIONS. WE MAY RISE INTO MVFR
CONDITIONS AFTER MIDNIGHT TONIGHT. ..LE..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
LE/12
000
FXUS63 KDMX 260933
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
333 AM CST THU FEB 26 2009
.SHORT TERM...(TODAY)
VERY COMPLEX FORECAST FOR TODAY WITH FREEZING RAIN ACROSS THE
WEST AND NORTH THIS MORNING EVENTUALLY SWITCHING OVER TO SNOW FAR
NORTH THIS AFTERNOON WITH AN EVENTUAL TRANSITION TO A MIX AND THEN
SNOW LATER TODAY. MODIFICATIONS FROM PREVIOUS PACKAGE INCLUDE
ADDING ANOTHER 3 COUNTIES TO THE ADVISORY FROM STORY EAST TO TAMA
COUNTIES...BUMPING UP SNOWFALL TOTALS ACROSS THE FAR NORTH AND
ALSO ADJUSTING THE AMOUNT OF EXPECTED ICE. AT THIS TIME...STILL
LOOKS LIKE BETWEEN .20 AND .30 OVERALL...BUT COMPLICATING THE
MATTER IS THE FACT THAT CONVECTION HAS ALREADY COMMENCED TO OUR
WEST WITH BUFKIT SOUNDINGS SHOWING INSTABILITY FARTHER NORTH INTO
THE COLDER AIR TODAY. THIS WOULD MEAN POSSIBLE THUNDER SLEET OR
THUNDER FREEZING RAIN OVER SOME AREAS THIS MORNING ESPECIALLY.
SO...WILL NEED TO BE KEEPING A CLOSE WATCH TODAY TO MONITOR IF
ANYTHING CHANGES. HAVE ADVISORY NOW BASICALLY ALONG AND NORTH OF
US 30 WITH WARNING AREAS REMAINING THE SAME. COLDER AIR TO FILTER
IN DURING THE AFTERNOON...BULK OF MOISTURE TRANSPORT SHIFTS TO THE
EAST SO EVEN AS CHANGEOVER OCCURS CENTRAL AND SOUTH...BULK OF
EXPECTED QPF TO ALREADY HAVE MOVED AWAY.
.LONG TERM...(TONIGHT-WED)
A STRONG 700 MB DRY PUNCH WILL MOVE OVER IOWA BY THIS EVENING
HOWEVER THE LOW LEVELS WILL REMAIN SATURATED BELOW THE DRY AIR
WITH SOME LIFT NEAR THE FRONTAL BOUNDARY AS IT MOVES SOUTHEAST.
THE DRY AIR ALOFT WILL RESULT IN NO ICE INTRODUCTION WITH ANY
PRECIPITATION ON THE COLD SIDE OF THE BOUNDARY BEING MAINLY LIGHT
FREEZING RAIN OR FREEZING DRIZZLE. THE PRECIPITATION WILL END FROM
WEST TO EAST BY 06Z.
A RELATIVELY COOL DAY IS ON TAP FOR FRIDAY WITH HIGHS ONLY
REACHING INTO THE MID TEENS OVER THE NORTH AS THE COLD AIR OVER
THE NORTHERN PLAINS DIPS SOUTH IN THE WAKE OF TODAYS SYSTEM.
ANOTHER STRONG SHORT WAVE WILL ARRIVE FRIDAY NIGHT AND WILL BRING
A ROUND OF LIGHT SNOW TO THE REGION. AT THIS TIME...SNOW
ACCUMULATIONS OF 1 TO 3 INCHES LOOK POSSIBLE. HIGHER AMOUNTS WOULD
BE POSSIBLE IF THE SYSTEM SLOWS DOWN AS IT PASSES THROUGH THE
STATE...HOWEVER THE GULF WILL BE CLOSED SO THE SYSTEM WILL ONLY
HAVE PACIFIC MOISTURE THAT HAS TAGGED ALONG FOR THE RIDE TO WORK
WITH AND WILL LIMIT OVERALL TOTALS. THE SNOW WILL BE ENDING
SATURDAY MORNING THEN THE REMAINDER OF THE WEEKEND WILL REMAIN
COOL AND DRY. BEYOND THAT A GRADUAL WARMING TREND IS ANTICIPATED
FOR THE BEGINNING OF NEXT WEEK.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR CERRO GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-
WINNEBAGO-WORTH.
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM CST THIS
AFTERNOON FOR BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-FRANKLIN-
GREENE-GRUNDY-HAMILTON-HARDIN-HUMBOLDT-MARSHALL-POCAHONTAS-STORY-
TAMA-WEBSTER-WRIGHT.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR
CARROLL-CRAWFORD-SAC.
&&
$$
SHORT TERM/AVIATION...REV/MJA
LONG TERM...DONAVON
000
FXUS63 KDMX 260529
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1130 PM CST WED FEB 25 2009
.UPDATED FOR THE 06Z AVIATION DISCUSSION...
.DISCUSSION...
STRONG STORM SYSTEM TAKING SHAPE TONIGHT OVER THE PLAINS WILL BEGIN
TO AFFECT CENTRAL IOWA MAINLY AFT 09Z. CLOUDS WILL BEGIN TO
INCREASE THIS EVENING WITH LOWER STRATUS MOVING IN AFT 06Z. THE ONE
CAVEAT INITIALLY IS A DRIER EASTERLY FLOW OVER CENTRAL IOWA THAT
WILL HAMPER SATURATION DURING THE OVERNIGHT. BY 12Z HOWEVER THE WIND
BECOMES MORE SOUTHERLY AS AN INVERTED TROUGH DEVELOPS TO THE SOUTH
AND WEST. WE SATURATE FAIRLY QUICKLY BY THEN BUT THAT IS NEAR THE
END OF THE FIRST PERIOD. OUR FAR WESTERN COUNTIES HOWEVER WILL
SATURATE A COUPLE HOURS EARLIER SO BETWEEN 09Z AND 12Z I EXPECT
PRECIP CHANCES TO INCREASE. SOUNDINGS INDICATE LIMITED MOISTURE AND
VERY SHALLOW AT THAT BUT SOME INSTABILITY WITH MU CAPES 300-400
J/KG. ISOLATED THUNDER IS WORTH A MENTION GIVEN THE AMOUNT OF LIFT
IN THE SOUTHWEST. TEMPS WILL BE TRICKY GIVEN THE AMOUNT OF COLD AIR
COMING DOWN. FOR NOW I KEPT THE NORTH BELOW FREEZING AND SOUTH OF
HIGHWAY 30 FLIRTING WITH FREEZING TO THE I-80 CORRIDOR. SOUTH OF
I-80 TEMPS WILL BE ABOVE FREEZING.
COMPLICATED WX STTN WITH SYS DVLP ON THU. IT WILL BE CLOSE ON THE
RN/FZRN AREA AND HAVE MOST CONCERN REGARDING THE FZRN. THE AREA A
FEW GUD ANALOG CASES...3/17/84...2/10/00 AND 3/8/03 FOR
EXAMPLE...BUT THERE IS A FAIR SPREAD ON THEM AS WELL. CUR PSN OF
THE WATCH AREA LKS REASONABLE AND WILL HOLD OFF ON UPGRADING ATTM AS
THE CRITICAL THING WILL BE THE QPF AMT. MDLS ARE GETTING MORE
CONSISTENT WITH QPF AMTS AND WILL NEED TO SEE JUST HOW MUCH FALLS IN
AQ FORM. R/S LN WL BE PRETTY SHARP AND ALNG THE BRDR. WILL GO WITH
CLOSE TO 4 INCHES ALONG THE MN LINE AND DON`T FEEL THERE WILL BE A
GREAT AMT OF FZRN IN THAT AREA...BUT A DIF STORY SOUTH. WILL SEE AT
LEAST A TENTH OR TO SOUTH OF THE AREA FM W CNTRL TWD N CNTRL
IA...BUT NOT A GREAT DEAL OF IP AND SN IN THOSE AREAS. FEEL WE ARE
LOOKING MORE TWD A HI END ADVY FOR NOW. RAIN AND TSRA TO THE S WITH
DECENT INSTABILITY SHWN BY THE SHOWALTER AND TQ INDICES. TEMPS WILL
BE STDY OR FALLING THU AFTN WITH READINGS FALLING A BIT BLO NORMAL
FOR MJUCH OF THE REST OF FCST PD. NEXT SYS ADVTZD TO MOVE THRU FRI
NGT INTO ERY SAT. FEEL ECMWF A BIT TOO FAR SOUTHWEST AND OPTED FOR
A COMPROMISE BETN THE GFS AND GEM SOLNS. NOT A BIG SYS WITH SNOW
FALL IN THE 1-2 INCH RANGE EXPECTED.
&&
.AVIATION...26/06Z
FORECAST HAS NOT BECOME MUCH CLEARER WITH THE AMOUNT OF COLD AIR
ASSOCIATED WITH THIS SYSTEM MOVING THROUGH THURSDAY STILL GOING TO
PRESENT A TRICKY PRECIPITATION TYPE FORECAST. FOR NOW LOOKS LIKE
KFOD...WILL SEE MOSTLY FZRA TRANSITIONING TO LIGHT SN OR PL. KALO
WILL SEE -RA CHANGING TO FZRA...THEN TO PL OR SN. FURTHER NORTH AT
KMCW...EXPECT FZRA TO CHANGE TO PL AND FINALLY SN INTO THE AFTERNOON
HOURS. EXPECT VSBYS TO DROP THE MOST AT KMCW WITH THE POSSIBILITY
FOR HEAVY SNOW. OTHERWISE SURFACE TEMPERATURES TO STAY WARM ENOUGH
FOR RAIN AT BOTH KDSM AND KOTM THROUGHOUT MUCH OF THURSDAY...WITH
THE CHANCE FOR THUNDERS STILL PRESENT. SOME MIXED PRECIP POSSIBLE AT
THE SOUTHERN SITES AS PRECIPITATION TAPERS OFF THURSDAY NIGHT. CIGS
TO GRADUALLY BECOME IFR/LIFR WITH THE ONSET OF PRECIPITATION BY
THURSDAY MORNING. ISSUE TOWARD THURSDAY EVENING ALSO WITH FREEZING
DRIZZLE WHICH COULD IMPACT ALL TAF SITES.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 AM TO 6 PM CST THURSDAY FOR CERRO
GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-WINNEBAGO-WORTH.
WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST THURSDAY FOR BLACK
HAWK-BOONE-BREMER-BUTLER-CALHOUN-FRANKLIN-GREENE-GRUNDY-HAMILTON-
HARDIN-HUMBOLDT-POCAHONTAS-WEBSTER-WRIGHT.
WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM CST THURSDAY FOR
CARROLL-CRAWFORD-SAC.
&&
$$
SHORT TERM...FAB
LONG TERM...MS FEB 09
AVIATION...MJA
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