Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 291730
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1230 PM CDT WED APR 29 2015

...UPDATED AVIATION...

.SHORT TERM /TODAY/...
ISSUED AT 309 AM CDT WED APR 29 2015

YET ANOTHER PLEASANT AND ABOVE NORMAL DAY IN STORE FOR CENTRAL
IOWA. DEPARTING MOISTURE STARVED SHORTWAVE WILL CLEAR THE STATE BY
12Z THIS MORNING. THE FORECAST AREA REMAINS WITHIN WEAK NORTHERLY
FLOW THROUGHOUT THE DAY BUT THERE IS ENOUGH MIXING THAT DEVELOPS
LATER THIS MORNING AND INTO THE AFTERNOON TO GO ABOVE MAJORITY OF
GUIDANCE FOR HIGHS TODAY. THE ADJMAV MOS SEEMED TO DO THE BEST WRT
TO MAX TEMPS TUESDAY AND IS AGAIN THE WARMEST FOR TODAY AND LEANED
TOWARDS THAT MODEL SOLUTION AS THE NAM/ECMWF/SREF AND RAW GFS ARE
TOO COOL FOR HIGHS TODAY. THIS RESULTED IN RAISING TEMPS 1-3
DEGREES ACROSS MUCH OF THE FORECAST AREA. THERE LOOKS TO BE SOME
FAIR-WEATHER CU TO DEVELOP TODAY...MAINLY IN THE SOUTHERN PORTIONS
OF THE STATE...BUT SHOULD NOT BE THICK OR WIDESPREAD ENOUGH TO
HOLD TEMPS DOWN. DID HOWEVER INCREASE SKY COVER TO MENTION MOSTLY
SUNNY.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 309 AM CDT WED APR 29 2015

NOT MUCH CHANGE FROM PREVIOUS FORECAST. THROUGH THURSDAY CONDITIONS
WILL REMAIN DRY. MODELS CONTINUE TO DIFFER ON DETAILS FOR THURSDAY
WITH THE GFS STILL THE ODD MODEL OUT. A BACKDOOR COLD FRONT WILL
MOVE SOUTH THROUGH THE REGION TODAY...SHOWING UP NICELY AT H850 AND
ALSO THICKNESS GRADIENT BACKING INTO EASTERN AND CENTRAL IOWA
THROUGH THE NEXT 24 HOURS. THE NAM/EURO/GEM CONTINUE TO EMPHASIZE
THE WESTWARD EXPANSION OF THE COOLER AIRMASS WHILE THE GFS QUICKLY
BEGINS TO SHOVE THE ENTIRE AIRMASS EAST BY 18Z THURSDAY WARMING H850
TEMPS 2C MORE BY 00Z COMPARED TO THE OTHER MODELS. GREAT LAKES HIGHS
TEND TO BE DIFFICULT TO DISLODGE AND WITH THE EXPANSIVE HIGH
AMPLITUDE RIDGE OVER THE WESTERN PLAINS...AM DOUBTFUL ABOUT THE GFS
SOLUTION. HAVE AGAIN LOWERED TEMPERATURES THURSDAY BUT MAINLY FOR
THE METRO...KEEPING AFTERNOON HIGH THERE IN THE LOWER 70S WITH 60S
ELSEWHERE. LIGHT WINDS AND LITTLE MIXING WITH POTENTIAL FOR CU
DURING THE DAY ALL POINT TO A PLEASANTLY MILD DAY...BUT CERTAINLY
NOT AS WARM AS TUESDAY AND TODAY. LOOKING AHEAD TO FRIDAY WITH THE
ARRIVAL OF A PACIFIC BOUNDARY INTO NORTHWEST IOWA BY 12Z. LITTLE
RECOVERY IN TERMS OF MOISTURE BUT AM EXPECTING SOME SHOWERS TO
SPREAD ACROSS THE AREA DURING THE DAY. MODELS AT ODDS FOR CONVECTION
...GFS TRIES TO PROMOTE SOME MUCAPE BUT GEM/EURO ARE BOTH NIL ON
CAPE. AIRMASS WILL NEED TO MOISTEN FIRST...LIKELY DIMINISHING ANY
CONVECTIVE ACTIVITY SO HAVE REMOVED ANY MENTION OF THUNDER FOR
FRIDAY. SIMILAR TO YESTERDAY MODEL PACKAGES...THE WEEKEND GETS
MORE INTERESTING. THE OLD BOUNDARY BECOMES ORIENTED EAST WEST AND
QUASI STATIONARY OVER NORTHERN MISSOURI BY 12Z SATURDAY. THIS WILL
RESULT IN OVERRUNNING SHOWERS AND PERHAPS ISO THUNDER ACROSS THE
SOUTH LATE FRIDAY NIGHT AND SATURDAY MORNING AS THE FRONT BECOMES
ACTIVE...BUT SOME UNCERTAINTY OF HOW MUCH CONVECTION VS SHOWERS
DEVELOPS...AND IF THE SHOWERS WILL MOVE SOUTH INTO MISSOURI WITH
TIME. WILL KEEP CHANCE SHOWERS OVER THE SOUTH FOR NOW ON SATURDAY.
MODELS IN GOOD AGREEMENT WITH FRONT LIFTING NORTH SATURDAY EVENING
INTO SUNDAY WITH POTENTIAL FOR CONVECTION TO DEVELOP AS LOW LEVEL
JET INTENSIFIES OVERNIGHT INTO SUNDAY. LIKELY THE FRONT LIFTING
NORTH WILL TAKE THE BETTER DYNAMICS AND RAIN CHANCES INTO NORTHERN
AND EASTERN IOWA SUNDAY AFTERNOON...LEAVING THE WEST AND SOUTH IN
THE WARM SECTOR. GEM/GFS AND TO A LESSER EXTENT EURO ALL SUGGEST
THAT H850 TEMPS WILL WARM INTO THE MID TO UPPER TEENS BY 00Z
MONDAY...BUFFETED BY SW WINDS OF 15 TO 25 KTS ALOFT. THIS SHOULD
PROMOTE MIXING WITH HIGHS REACHING AT MINIMUM THE LOWER 80S OVER
MUCH OF THE SOUTH...WITH DEW POINTS IN THE LOWER TO MID 50S
FEELING A BIT MORE SUMMER LIKE. AS THE SFC TROUGH AND PACIFIC
COLD FRONT SINK SOUTH ACROSS THE AREA SUNDAY EVENING THE FRONT
SHOULD LIGHT UP WITH THUNDERSTORMS...PERHAPS A FEW STRONG BUT
LIKELY NOT MUCH THREAT FOR ANY ORGANIZED SVR WEATHER AS UPPER
LEVEL WINDS ARE GENERALLY WEAK. RAINFALL WILL BE THE MAIN BENEFIT
WITH POTENTIAL FOR AN INCH OR MORE NEARER THE BOUNDARY ACROSS THE
SOUTH MONDAY... BUT MOST OF THE AREA SEEING UP TO AN INCH.
DEPENDING ON THE TIMING OF THE SYSTEM...AND IT APPEARS THAT
CONFIDENCE IS LESSENING FOR IT TO HAVE EXITED THE REGION BY 00Z
TUESDAY...WE MAY BE LOOKING AT SHOWERS AND STORMS INTO TUESDAY.
THE FRONT IS EXPECTED TO STALL NEAR IOWA NEXT WEEK...KEEPING THE
AREA IN LINE FOR THE POTENTIAL FOR A WET WEEK WITH MORE SHOWERS
AND THUNDERSTORMS AND COOLER TEMPERATURES REGIONWIDE...60S TO
LOWER 70S.

&&

.AVIATION...29/18Z
ISSUED AT 1227 PM CDT WED APR 29 2015

QUIET TAF PERIOD WITH HIGH PRESSURE IN THE REGION. VFR CONDITIONS
THROUGHOUT WITH ONLY SOME FAIR WEATHER CUMULUS TODAY AND WINDS
AROUND 10 KTS OUT OF THE NORTH AND GUSTS TO AROUND 15 KTS AT
TIMES BEFORE SUBSIDING THIS EVENING.

&&

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

$$

SHORT TERM...PODRAZIK
LONG TERM...REV
AVIATION...CURTIS



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