Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 180437
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1137 PM CDT FRI OCT 17 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 351 PM CDT FRI OCT 17 2014

UPPER LOW SPINNING ACROSS NE WISCONSIN ATTM...SHOULD CONTINUE TO
PUSH EAST TONIGHT. ANOTHER WEAK WAVE TO DIG INTO THE BACKSIDE OF THE
PARENT UPPER LOW DROPPING SOUTHWARD THROUGH MINNESOTA INTO NRN/NERN
IOWA TONIGHT. THIS WILL SEND A REINFORCING SHOT OF COLD AIR AND
ALLOW CLOUD COVER TO REMAIN ACROSS THE NORTHERN/EASTERN PORTION OF
THE CWA. DRIER AIR CONTINUES TO WORK ITS WAY INTO THE
WESTERN/SOUTHERN PORTION OF THE CWA...WHICH SHOULD LIMIT THE CLOUD
COVER SOME IN THOSE AREAS THROUGHOUT THE OVERNIGHT HOURS. OTHERWISE
WINDS EXPECTED TO DIMINISH SOME AS THE SFC PRS GRADIENT RELAXES AND
SFC HIGH PRESSURE BUILDS INTO THE CENTRAL PLAINS/WRN IOWA. WITH LESS
CLOUDS EXPECTED ACROSS THE SOUTHWEST...HAVE COOLEST TEMPS IN THAT
AREA. OVERALL COOLING SHOULD BE LIMITED BY THE CLOUD COVER AND SOME
WIND ACROSS THE NORTH/EAST.

.LONG TERM /SATURDAY THROUGH FRIDAY/...
ISSUED AT 351 PM CDT FRI OCT 17 2014

SATURDAY WILL BE THE COOLEST DAY IN THE FORECAST AS LAST ROUND OF
COLD ADVECTION MOVES AHEAD OF THE DAY TONIGHT. HIGHS WILL
GENERALLY BE IN THE 50S. SOME POTENTIAL FOR STRATUS TO LINGER OVER
THE FAR NORTHEAST SATURDAY MORNING OTHERWISE SKY CONDITIONS WILL
CLEAR AS HIGH PRESSURE ARRIVES FROM THE WEST. THE HIGH PRESSURE
WILL REMAIN PROGRESSIVE SATURDAY EVENING AND SHIFT QUICKLY TO THE
EAST WITH RETURN FLOW DEVELOPING BY MID TO LATE EVENING. MID LEVEL
WARM ADVECTION WILL BE ONGOING THROUGH MUCH OF THE DAY SUNDAY. A
COUPLE POTENTIAL IMPACTS INCLUDE CLOUD COVER WHICH COULD LIMIT
HIGH TEMPERATURES DESPITE GOOD SOUTHWEST SFC FLOW AND LOW
PRECIPITATION CHANCES. HAVE REMAINED DRY FOR SUNDAY WITH THE
PRIMARY KINEMATICS REMAINING TO THE NORTHWEST ACROSS THE WESTERN
GREAT LAKES. THERE WILL BE A BRIEF PERIOD WHERE WEAK FORCING ALONG
A NARROW AXIS OF SATURATION COULD PRODUCE SPRINKLES BUT WILL NOT
BE MUCH OF AN IMPACT TO THE FORECAST.

SOME MODEL DISCREPANCIES WITH THE AMOUNT OF COLD AIR WILL SETTLE
INTO IOWA ON MONDAY BEHIND THE SUNDAY NIGHT SHORT WAVE MOVING
THROUGH THE NW FLOW. HAVE FOLLOWED A ECMWF/GEM MEAN WHILE
REMOVING THE COLDER GFS AND WARMER NAM. HIGH PRESSURE RIDGE WILL
MOVE SLOWLY EAST MID NEXT WEEK. AS ALLUDED TO YESTERDAY...EXPECT
THE GENERAL PATTERN TO SLOW AS THE LARGE UPPER LOW CHURNS OVER THE
EASTERN CONUS. THIS WILL LEAVE A LARGE SFC RIDGE OF HIGH PRESSURE
FROM THE CENTRAL GREAT LAKES SOUTHWEST THROUGH THE CENTRAL TO
LOWER MISSISSIPPI VALLEY. SOUNDINGS THROUGH THIS PERIOD ARE TRYING
TO HOLD A SIGNIFICANT INVERSION AS VERY WARM 850 MB AIR MOVES
ACROSS THE AREA WHILE COOLER EAST TO SOUTHEAST FLOW UNDERCUTS THE
WARMER AIR. OVERALL...GOING FORECAST STILL LIKELY TOO COOL WITH A
PERIOD OF DRY WEATHER WITH INCREASING SOUTHERLY WINDS BY THURSDAY.
HAVE OPTED MOSTLY DRY DURING THIS PERIOD WITH THE WESTERN TROUGH
NOT QUITE ARRIVING. POTENTIAL FOR SUPER ADIABATIC MIXING WILL
INCREASE AS WELL THEREFORE STILL NOT DISCOUNTING ANOTHER BOUT WITH
THE 70S FOR LATE OCTOBER.

&&

.AVIATION...18/06Z
ISSUED AT 1137 PM CDT FRI OCT 17 2014

THE LARGE STRATOCUMULUS SHIELD HAS CONTINUED TO CREEP SOUTHWARD AS
EXPECTED...HOWEVER CIG HEIGHTS HAVE BEEN MORE VARIABLE THAN
ANTICIPATED RANGING ANYWHERE FROM FL017 TO FL048. SATELLITE
IMAGERY ALSO DEPICTS A LARGE HOLE MOVING FROM SOUTHERN MINNESOTA
INTO NORTHERN IOWA IN WHICH SKIES ARE VIRTUALLY CLEAR BEFORE
FILLING IN AGAIN FURTHER NORTH. ALL IN ALL STILL EXPECT BKN-OVC
MOST OF THE TIME THROUGH SAT MORNING BEFORE THE CLOUDS FINALLY
BEGIN TO CLEAR OUT...HOWEVER JUDGING FROM RECENT AND UPSTREAM
OBS...PERIODS OF MVFR WILL REMAIN POSSIBLE FOR AT LEAST THE NEXT
8 HOURS BUT DIFFICULTY OF PREDICTING EXACT TIMING AND LIMITED
OVERALL EXTENT DICTATE MOSTLY VFR CIGS ADVERTISED IN THE TAFS
ATTM.

&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...DONAVON
AVIATION...LEE


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