Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 231750
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1250 PM CDT MON MAR 23 2015

.SHORT TERM /TODAY/...
ISSUED AT 330 AM CDT MON MAR 23 2015

A DEVELOPING LOW PRESSURE CENTER IS MOVING ACROSS SOUTHERN IOWA
EARLY THIS MORNING...WITH A LARGE CLOUD SHIELD ALONG ITS NORTHERN
AND EASTERN FLANKS COVERING MOST OF OUR FORECAST AREA EXCEPTING THE
SOUTHWEST. WINDS ARE BRISK AROUND THE LOW BUT THE CLOUDS HAVE KEPT
TEMPERATURES IN THE UPPER 20S TO MID 30S AT MOST LOCATIONS...WITH
LAMONI CURRENTLY HOLDING AT 49 JUST SOUTHEAST OF THE CENTER OF THE
LOW BUT COOLER AIR RAPIDLY APPROACHING. MOST PRECIPITATION HAS
CLEARED OUR AREA TO THE EAST...WITH SOME LIGHT SNOW LINGERING IN THE
FAR NORTH AND SCATTERED SHOWERS AND THUNDERSTORMS EXITING TO THE EAST.

ALL PRECIPITATION WILL END IN THE DMX FORECAST AREA BY AROUND
SUNRISE...WITH VERY LITTLE ACCUMULATION BETWEEN NOW AND THEN. ICY OR
SNOWY ROAD CONDITIONS MAY HOLD IN THE NORTH DUE TO THE WINTRY PRECIP
THAT HAS BEEN FALLING AND ROAD TEMPS A LITTLE BELOW FREEZING.
HOWEVER...AS THE PRECIP ENDS WITHIN THE NEXT FEW HOURS EXPECT ROAD
CONDITIONS WILL THEN STEADILY IMPROVE THROUGH THE MORNING. SATELLITE
IMAGERY INDICATES THAT THE LARGE CLOUD SHIELD AROUND THE DEVELOPING
LOW IS EXPANDING BACK TO OUR NORTHWEST IN OPPOSITION TO WHAT SHORT
RANGE MODELS ARE PREDICTING...THUS HAVE INCREASED SKY COVER FORECAST
FROM PREVIOUS ISSUANCE AND HAVE CONCERNS ABOUT THE DEGREE OF WARMING
TODAY PARTICULARLY WITH A COOLER MASS OF AIR AND WEAK HIGH PRESSURE
RIDGE TO OUR NORTHWEST SLATED TO BUILD ACROSS THE AREA THIS
AFTERNOON IN WAKE OF THE DEPARTING LOW. HAVE COOLED OFF FORECAST
HIGHS A COUPLE OF DEGREES AS A RESULT.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 330 AM CDT MON MAR 23 2015

TODAYS SYSTEM WILL BE SOUTHEAST OF THE AREA BY THIS EVENING
HOWEVER RETURN FLOW WILL ALREADY BE DEVELOPING INTO SOUTHWEST AND
SOUTH CENTRAL IOWA. THETA-E ADVECTION WILL BEGIN TO SPREAD INTO
THE SOUTH MID TO LATE EVENING AS A 50 KT LOW LEVEL JET DEVELOPS
IN ADVANCE OF A POTENT SHORT WAVE/PV ANOMALY APPROACHING FROM THE
WEST. SHOWERS AN A FEW ISOLATED THUNDERSTORMS ARE POSSIBLE WITH
THIS ACTIVITY OVER SOUTHERN IOWA. THE PRECIPITATION WILL LIFT
NORTH BUT SHOULD GRADUALLY DIMINISH IN AREAL COVERAGE DURING THE
MORNING. TEMPERATURES WILL BE NEAR FREEZING NORTH OF INTERSTATE 80
THEREFORE THE INITIAL PRECIPITATION TYPE MAY BE FREEZING RAIN
BEFORE TEMPERATURES RISE. THE PRIMARY PRECIPITATION SHIELD WILL
ARRIVE MID AFTERNOON THROUGH MID EVENING AS STRONG QG FORCING
SPREADS ACROSS THE STATE WITH THE ARRIVAL OF THE UPPER LEVEL
SYSTEM. THE NAM CONTINUES TO SUGGEST THE 1.5 POTENTIAL VORTICITY
PRESSURE WILL DROP DOWN TO 900 MB WITH A TIGHTENING GRADIENT ALONG
THE LEADING EDGE LEADING TO ENHANCED FORCING. MUCAPES INTO FAR
SOUTHERN IOWA WILL BE NEAR 500-700 J/KG AND WILL BE SUFFICIENT TO
SUSTAIN A FEW STRONG UPDRAFTS INTENSE ENOUGH TO SUPPORT MARGINALLY
SEVERE SIZED HAIL. THE SFC LOW PRESSURE STILL ON TRACK TO MOVE
ACROSS THE FAR SOUTHEAST FORECAST AREA NEAR CENTERVILLE TO
OTTUMWA. SHOULD THIS OCCUR...THERE WILL BE A THREAT FOR DAMAGING
WIND GUSTS SOUTH OF THE LOW TRACK AS STORMS TRY TO BECOME SURFACE
BASED. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO BE
WIDESPREAD THROUGH CENTRAL AND NORTHERN IOWA DURING THIS PERIOD AS
THE SYSTEM MOVES THROUGH.

THE FORECAST FOR WEDNESDAY IS CHANGING A BIT AS ANOTHER SHORT
WAVE APPROACHES THE AREA. TEMPERATURES ARE EXPECTED TO BE MILD
ACROSS THE SOUTH AND IN THE 50S AND LOW 60S WITH COOLER CONDITIONS
NORTH. HAVE INTRODUCED PRECIPITATION CHANCES FOR THE AFTERNOON AS
THE FORCING ARRIVES. THE SYSTEM WILL HAVE TO FIGHT DRY AIR IN
PLACE IN THE WAKE OF THE TUESDAY SYSTEM BUT FORCING AND MID LEVEL
SATURATION IS SUFFICIENT THAT SHOULD BE ABLE TO HAVE LIGHT
PRECIPITATION DEVELOP ACROSS PORTIONS OF THE AREA. MUCH COLDER AIR
WILL DROP INTO THE MIDWEST WEDNESDAY NIGHT THROUGH FRIDAY FOLLOWED
BY MODERATION INTO THE WEEKEND.

&&

.AVIATION...23/18Z
ISSUED AT 1239 PM CDT MON MAR 23 2015

MAIN CONCERNS CONTINUE TO BE STRATUS FIELD AND CIGS THROUGH
06Z ALONG WITH EVENTUAL PRECIP CHANCES TOWARD 12Z. NORTHEAST FLOW
HAS ALLOWED FOR COOLER TEMPS AND STRATUS TO HOLD ONTO CENTRAL AND
EASTERN AREAS FOR NOW...OVERNIGHT APPROACHING SYSTEM WILL NEED TO
OVERCOME DRY AIR ALOFT PRIOR TO PRECIP ONSET. OVER THE SOUTHEAST
THERE CONTINUES TO BE A THREAT FOR -FRZA BASED ON COOLING TONIGHT
WITH IS0 TO SCT THUNDER ALSO POSSIBLE AFT 13Z AS INSTABILITY
DEVELOPS AT MID LEVELS. HAVE ADDED 3 HOUR PERIOD OF -FZRA TO KOTM
PRIOR TO POTENTIAL THUNDER. ELSEWHERE...OVER THE NORTH CIGS TO
REMAIN LOW AND PRECIP DELAYED TOWARD END OF PERIOD. /REV


&&

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

$$

SHORT TERM...LEE
LONG TERM...DONAVON
AVIATION...REV



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