Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 211137
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
637 AM CDT THU MAY 21 2015

.SHORT TERM /TODAY/...
ISSUED AT 337 AM CDT THU MAY 21 2015

FEW CONCERNS TODAY. SOME PATCHY FOG HAS DEVELOPED OVER THE
SOUTHEAST AND WILL ADD THROUGH ABOUT 12Z. AT H850 THE TROUGH
THAT BROUGHT SHOWERS AND RECORD LOW MIN MAXES TO THE AREA TODAY IS
NOW OVER INDIANA AT 00Z. COLD POCKET ALOFT STILL HELPING TO KEEP
LINGERING STRATUS IN PLACE OVER THE SOUTHEAST WITH ACCOMPANYING
CYCLONIC FLOW ALOFT...SYSTEM PULLING OUT BY 12Z. THE REGION WILL
BE CAUGHT BETWEEN A REGION OF HIGH PRESSURE OVER THE CENTRAL
PLAINS SLOWLY DRIFTING SOUTHEAST AND A SECOND COLD FRONT OVER
NORTH CENTRAL MN EXPECTED TO DROP SOUTH INTO NORTHERN IOWA BY 00Z
FRIDAY. CURRENTLY A FEW MID LEVEL CLOUDS ALONG THE BOUNDARY OVER
NORTHERN MN. THESE SHOULD MAKE THEIR WAY INTO NORTHERN AND PERHAPS
CENTRAL IOWA BY 00Z TONIGHT. MEANWHILE... SFC WINDS HAVE BECOME
MORE WEST SOUTHWESTERLY. WITH WARMING H850 TEMPS TODAY...REACHING
9 TO 10C AS ADIABATIC WARMING OVER THE NORTHERN PLAINS IS DRAWN
SOUTHEAST...HIGHS SHOULD RECOVER INTO THE UPPER 60S TO LOWER 70S
OVER THE AREA. WINDS WILL BE BREEZY BY AFTERNOON WITH GUSTS
REACHING 20 TO 30 MPH...HIGHER OVER THE NORTH THIS AFTERNOON.
AMBIENT WINDS WILL BE IN THE RANGE OF 13 TO 20 MPH BY AFTERNOON.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 337 AM CDT THU MAY 21 2015

MAIN FORECAST CONCERN WAS FOCUSED ON THE ACTIVE WEATHER PATTERN
BEGINNING THIS WEEKEND AND LASTING INTO NEXT WEEK. MODELS ARE IN
FAIR AGREEMENT THROUGH SATURDAY BEFORE THE BIGGER DISCREPANCIES
SHOW UP SATURDAY NIGHT INTO NEXT WEEK. AT LEAST THE EXTENDED
MODELS AGREE ON THE WARMER TEMPERATURES AND ACTIVE WEATHER PATTERN
NEXT WEEK. TEMPERATURES REBOUND AND BECOME MORE SEASONAL BY FRIDAY
AND THROUGH THE WEEKEND...THEN ABOVE NORMAL BY MEMORIAL DAY
THROUGH NEXT WEEK.

TONIGHT THROUGH MEMORIAL DAY...COOL AND DRY TONIGHT WITH THE
SURFACE HIGH OVERHEAD BEFORE SHIFTING EAST FRIDAY ALLOWING FOR
SOME WEAK RETURN FLOW TO DEVELOP LATE IN THE DAY. THIS RETURN FLOW
SHOULD BE ENOUGH TO GO SLIGHTLY WARMER FOR MAX TEMPS FRIDAY AND
BUMPED THEM UP A COUPLE DEGREES. THE LARGE SURFACE HIGH IS SLOW
TO MOVE EAST AND MODELS CONTINUE SLOWING DOWN PRECIPITATION INTO
CENTRAL IOWA UNTIL SATURDAY NIGHT. NAM/GFS DO HAVE SOME WEAK MID-
LEVEL THETA-E ADVECTION PUSHING NORTHEASTWARD INTO THE AREA
SATURDAY MORNING...SO MAY SEE SOME WEAK ELEVATED SHOWERS DEVELOP
OVER THE WEST. HOWEVER...PRETTY DRY BELOW 800MB MUCH OF THE DAY
AND NOT ANTICIPATING MUCH QPF. LOWERED AND DELAYED POPS FRIDAY
NIGHT UNTIL AFTER 09Z TO JUST THE FAR SOUTHWEST AND WEST OF
INTERSTATE 35 B/T 12-18Z SATURDAY. THE ECMWF KEEPS MUCH OF THE
STATE DRY THROUGH EARLY SUNDAY MORNING AND THINKING IT HAS THE
BEST HANDLE ON THE SURFACE RIDGE TO THE EAST SLOWING THE
PROGRESSION OF NEXT DEEP TROUGH LOCATED OVER THE FOUR CORNERS
REGION DURING THE WEEKEND. LOWERED POPS SATURDAY AFTERNOON AND
EVENING...WITH THE HIGHER POPS OVER THE SOUTH. WITH THE GFS/ECMWF
IN SOME AGREEMENT WITH SUNDAY BEING WET ALL DAY...INCREASED POPS
TO CATEGORICAL ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. VERY
GOOD MOISTURE TRANSPORT AND DEEP MOISTURE INTO THE STATE WITH SOME
WEAK INSTABILITY AND BROAD AREA OF WEAK QG FORCING PRESENT ON
SUNDAY. SEVERE POTENTIAL APPEARS MINIMAL ATTM WITH THE LACK OF ANY
SIGNIFICANT INSTABILITY AND SHEAR AVAILABLE.

TUESDAY INTO THURSDAY...WARM AND HUMID CONDITIONS FINALLY RETURN
TO THE STATE DURING THIS PERIOD BUT THE DOWN SIDE IS THE ACTIVE
WEATHER PATTERN THROUGHOUT MID-WEEK. THE REGION STAYS IN
SOUTHWEST FLOW ALOFT WITH SEVERAL SHORTWAVES TRAINING EACH OTHER
MONDAY THROUGH WEDNESDAY...DEPENDING ON WHICH EXTENDED
MODEL...TIMING AND LOCATION IS CHALLENGING TO PIN DOWN AT THIS
POINT. KEPT CHANCE POPS GOING FOR MUCH OF EXTENDED AND MAY SEE A
DRY PERIOD LATE MONDAY NIGHT INTO TUESDAY. CONFIDENT ENOUGH TO GO
SLIGHTLY ABOVE GUIDANCE FOR HIGHS NEXT WEEK WITH THE WARM 850MB
TEMPS AND DECENT MIXING EACH AFTERNOON.

&&

.AVIATION...21/12Z
ISSUED AT 626 AM CDT THU MAY 21 2015

MAIN CONCERN IS EARLY MORNING FOG SOUTHEAST. DENSE FOG AT KOTM
SHOULD LIFT BY 14Z WITH REMAINDER OF AREA SKC OR SOME MID LEVEL
CLOUDS ACROSS THE NORTH AFT 16Z. OTHERWISE WINDS EXPECTED TO
INCREASE ACROSS THE NORTH WITH GUSTS TO NEAR 30 KTS. WINDS WILL
DECREASE BY 00Z MOST AREAS WITH VFR CONDITIONS EXPECTED THROUGH
END OF PERIOD.

&&

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

$$

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


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