Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 042042
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
242 PM CST WED MAR 4 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 242 PM CST WED MAR 4 2015

SECONDARY COLD FRONT PUSHING THROUGH THE CWA WITH ANOTHER SURGE OF
ARCTIC AIR BEHIND IT. H85 TEMPS INTO THE TEENS BELOW ZERO CELSIUS BY
LATE TONIGHT. ARCTIC HIGH BUILDING INTO THE CWA TO BE CENTERED OVER
THE STATE BY 12Z. SKIES EXPECTED TO CLEAR THIS EVENING...WITH WINDS
DIMINISHING AS WELL. THEREFORE EXPECT TEMPS TO DROP OFF AND BECOME
QUITE COLD BY MORNING. SITES WITH A DECENT SNOWPACK EXPECTED TO BE
WELL BELOW ZERO...AND OTHERS WITH LITTLE OR NO SNOW AROUND ZERO OR
SLIGHTLY ABOVE. WIND CHILLS WILL FALL TO AROUND -15 TO -20 BY SUNRISE
THURSDAY MAINLY IN THE NORTH/EAST...BUT WIND SPEEDS ARE EXPECTED TO
BE VERY LIGHT THUS WILL REFRAIN FROM ISSUING ANY HEADLINE AT THIS
TIME.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 242 PM CST WED MAR 4 2015

MAIN CHALLENGES THROUGH THE EXTENDED WITH BE THE EXTENT OF THE
WARMING OVER THE NEXT SEVEN DAYS AS H500 ANCHOR LOW OVER EASTERN
CANADA BEGINS TO SHIFT EAST...ALLOWING FOR A RETURN OF ZONAL FLOW
AND PERSISTENT ADIABATIC WARMING ACROSS THE CENTRAL PLAINS. CONFIDENCE
TOWARD THE END OF THE PERIOD BEGINS TO DROP WHEN THE MODELS DIVERGE
ON SOLUTIONS.

TONIGHTS SIGNIFICANT COLD AIRMASS WITH H850 TEMPS AS LOW AS -25C
OVER MUCH OF THE NORTHERN PLAINS THIS MORNING/EASTERN GREAT LAKES BY
12Z THURS WILL MOVE EAST AS THE STRONG SHORTWAVE/JET ENERGY SOUTH OF
IOWA TODAY LIFTS THE EASTERN CANADA WAVE INTO NORTHERN QUEBEC. THIS
WILL ALLOW FOR A MORE WNW TRAJECTORY OF COLD AIR MASSES/SHORT WAVES
ACROSS SOUTHERN CANADA...SHIFTING THE STORM TRACK NORTH AND EAST OF
THE AREA RATHER THAN SOUTH/SOUTHEAST INTO THE NORTHERN PLAINS/GREAT
LAKES. WITH SOUTHWEST FLOW ALOFT TOMORROW...H850 TEMPS RECOVER
FROM -16C AT 12Z TO -12C BY 00Z FRIDAY. SOUTHEAST SFC FLOW WILL
NOT REALIZE THE ENTIRE COLUMNS WARMING...SO HIGHS WILL ONLY REACH
THE TEENS TO UPPER 20S...WITH THE COOLEST READINGS NORTHEAST. SOME
MID LEVEL CLOUDS WILL ALSO BRUSH NORTHEAST IOWA HELPING TO KEEP
TEMPS LOWER THERE AS WELL. BY THURSDAY NIGHT/FRIDAY STRONGER
SOUTHERLY FLOW WILL RETURN WITH ANOTHER PUSH OF WARM AIR
ADVECTION. FRIDAY AFTERNOON H850 TEMPS WILL RANGE FROM NEAR 0C
NORTHEAST TO +3C IN THE SOUTHWEST. THIS WOULD NORMALLY PRODUCE
HIGHS IN THE MID 30S TO AROUND 50F OVER THE SAME H850 RANGE...AND
HAVE BUMPED HIGHS A DEGREE OR TWO HIGHER MOST AREAS. THE ONLY
DETERRENT TO WARMER TEMPS MAY BE THE RESIDUAL SNOW COVER ACROSS
IOWA...KANSAS...AND MISSOURI. THIS MAY HOLD TEMPS BACK...ESPECIALLY
NORTHEAST. MODEL GUIDANCE IS ALL OVER THE BOARD THE NEXT FEW DAYS
FOR TEMPS...WITH THE EURO MUCH WARMER THAN THE GFS/NAM. FOR NOW...
WILL USE A BLEND FOR THE FIRST FEW DAYS OF THE EXTENDED GIVEN THE
SOUNDINGS ARENT COMPLETELY MIXED AND DONT REALIZE THE ENTIRE
COLUMN WARMING AND THERE IS SOME ADDITIONAL SNOW TO MELT. BY
FRIDAY NIGHT ANOTHER COLD FRONT WILL SLIDE SOUTHEAST AND BRIEFLY
CAP ANY POTENTIAL WARMING ON SATURDAY. HOWEVER...THE FAST MOVING
FLOW REMAINS IN PLACE AND WE WILL SEE ANOTHER AIRMASS WITH MILDER
READINGS SUNDAY. FURTHER WARMING WILL OCCUR MONDAY AND TUESDAY
WITH YET ANOTHER SHORTWAVE TRACKING ALONG THE US_CAN BORDER
MONDAY INTO TUESDAY. THOUGH WE CONTINUE TO SEE WEAK FRONTAL
BOUNDARIES OSCILLATING SOUTH/RETREATING NORTH OVER IOWA THROUGH
THE END OF THE PERIOD...THE OVERALL TREND IS FOR WARMING THICKNESS
AND HEIGHTS ALOFT AS H500 RIDGING REPLACES THE PERSISTENT H500 LOW
OVER THE EASTERN CONUS OF THE PAST COUPLE OF WEEKS. THUS...WILL
CONTINUE TO SEE MILD WEATHER AND ABOVE NORMAL FOR A CHANGE. THE
MODELS DIVERGE AFTER WEDNESDAY WITH THE EVOLUTION OF THE
SOUTHWESTERN UPPER LEVEL SYSTEM LATE IN THE PERIOD. THE GFS
ATTEMPTS TO BRING THE SYSTEM EAST INTO THE CENTRAL PLAINS BY 00Z
THURSDAY WHILE THE 00 AND 12Z EURO/GEM CONTINUE TO HOLD THE SYSTEM
BACK OVER THE SOUTHWEST US FOR A FEW DAYS LONGER. GFS IS BIASED
TOO FAST AND WILL DELAY ANY PRECIP IN THE EXTENDED AT THAT TIME
AND KEEP TEMPERATURES MILDER OVER THE REGION. OVERALL HIGHS WILL
BE QUITE MILD FROM MONDAY THROUGH THURSDAY WITH READINGS IN THE
50S TO 60S AT TIMES. THE WARMEST DAYS APPEAR TO BE WEDNESDAY AND
THURSDAY WITH HIGHS IN THE 50S TO 60S ACROSS THE REGION.

&&

.AVIATION...04/18Z
ISSUED AT 1151 AM CST WED MAR 4 2015

SECONDARY COLD FRONT TO DROP THROUGH THE CWA THIS AFTERNOON INTO
EARLY EVENING...EXPECT SOME CLOUDS ALONG THE FRONT AND GUSTY
WINDS. MAY SEE SOME FLURRIES DEVELOP AS WELL...BUT HAVE REFRAINED
FROM MENTIONING IN THE TAF AT THIS TIME. CLOUDS WITH THE FRONTAL
PASSAGE WILL BE IN THE SCT-BKN025-035 RANGE. OTHERWISE CLEAR
CONDITIONS ARE EXPECTED LATE TONIGHT INTO THURSDAY WITH DECREASING
WINDS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BEERENDS
LONG TERM...REV
AVIATION...BEERENDS


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