Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 272341
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
641 PM CDT SAT SEP 27 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 256 PM CDT SAT SEP 27 2014

UPPER LOW WILL CONTINUE TO DRIFT IN VICINITY OF NORTHWEST IOWA
OVERNIGHT WITH MAIN JET AXIS WELL NORTH INTO CANADA. ISOLATED
STORMS CONTINUE TO FIRE THIS AFTERNOON UNDERNEATH THE LOW IN
NORTHERN IOWA IN AN AREA OF LOW LEVEL THETA-E ADVECTION. THIS
ADVECTION WILL DIMINISH INTO THE OVERNIGHT AND ANTICIPATE THE
THREAT OF CONVECTION TO END LATER THIS EVENING. OTHERWISE...CU
FIELD WILL DISSIPATE WITH LOSS OF DAYTIME HEATING WITH GENERALLY
MOSTLY CLEAR SKIES AND LIGHT WINDS OVERNIGHT. MAY SEE THE
DEVELOPMENT OF SOME PATCHY FOG...ESPECIALLY IN LOCATIONS THAT HAVE
SEEN RAINFALL IN THE PAST DAY OR TWO BUT HAVE FOREGONE A MORE
WIDESPREAD MENTION AT THIS TIME IN THE ZONES AS RAINFALL HAS BEEN
RELATIVELY ISOLATED.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 256 PM CDT SAT SEP 27 2014

THE UPPER LEVEL LOW CURRENTLY OVER IOWA WILL SLOWLY FILL AND MOVE
OFF TO THE EAST SUNDAY AND SUNDAY NIGHT...BRINGING DRY AND
UNSEASONABLY MILD WEATHER TO END THE WEEKEND AND INTO EARLY NEXT
WEEK. BY MONDAY AFTERNOON A DYING COLD FRONT WILL APPROACH IOWA FROM
THE NORTH...BUT IT SHOULD BE WEAK ENOUGH BY THE TIME IT REACHES THE
BORDER THAT ANY SHOWERS OR STORMS ARE UNLIKELY. HAVE KEPT POPS OUT
OF THE FORECAST ALL THE WAY FROM SUNDAY INTO TUESDAY AND MADE LITTLE
CHANGE TO TEMPERATURES...EXCEPT TO BUMP UP HIGHS BY A DEGREE OR TWO
SUNDAY AND MONDAY AS IT APPEARS WEAK WARM AIR ADVECTION AND AMPLE
LATE SUMMER SUNSHINE SHOULD ALLOW US TO WARM INTO THE LOWER 80S IN
MANY AREAS.

BY TUESDAY MORNING SURFACE HIGH PRESSURE WILL BE BUILDING INTO IOWA
FROM THE NORTHEAST AND THE WEAK COLD FRONT WILL HAVE ESSENTIALLY
WASHED OUT...RESULTING IN EAST TO SOUTHEAST LOW LEVEL FLOW ACROSS
OUR FORECAST AREA AND MOSTLY SUNNY SKIES BY LATE MORNING.
HOWEVER...A BIG PATTERN CHANGE WILL BE ON OUR DOORSTEP AS A STRONG
500 MB LOW PRESSURE SYSTEM WILL SWING UP INTO NEBRASKA AND THE
DAKOTAS...WITH A SECOND ROBUST TROUGH ON ITS HEELS OVER BRITISH
COLUMBIA AND THE PACIFIC NORTHWEST. THE FIRST SYSTEM WILL GIVE US A
GLANCING BLOW AS IT CONTINUES NORTH NORTHEAST ACROSS THE DAKOTAS AND
INTO MINNESOTA...SPREADING SOME SHOWERS AND THUNDERSTORMS MAINLY
WEST OF I-35 FROM TUESDAY AFTERNOON THROUGH MOST OF TUESDAY NIGHT.
SPLIT THE TUESDAY POPS INTO SIX HOUR BLOCKS AS IT APPEARS THERE IS
LITTLE CHANCE OF ANY PRECIP REACHING OUR WESTERN COUNTIES BEFORE
NOON. ANOTHER 500 MB SHORTWAVE KICKING OUT OF THE HIGH PLAINS WILL
GENERATE ADDITIONAL SHOWERS AND STORMS FROM LATE TUESDAY NIGHT
THROUGH WEDNESDAY...THEN ANOTHER IMPULSE SWINGING AROUND THE TROUGH
WILL LIKELY GENERATE EVEN MORE RAIN FROM WEDNESDAY NIGHT THROUGH
THURSDAY...BEFORE THE FINAL LOBE OF VORTICITY MOVES OVER EARLY
FRIDAY ACCOMPANIED BY SHOWERS. ALL IN ALL THE PERIOD FROM TUESDAY
AFTERNOON INTO FRIDAY WILL BE CHARACTERIZED BY SEVERAL PERIODS OF
RAINFALL AND COOLER TEMPERATURES...ESPECIALLY TOWARD THE END OF THE
WEEK AS THE FINAL TROUGHS PASS THROUGH. LIKELY POPS ARE INCLUDED IN
THE FORECAST FOR MOST OF THE FORECAST AREA FROM TUESDAY NIGHT
THROUGH THURSDAY. A RELATIVE LACK OF INSTABILITY AND STRONG LOW
LEVEL WIND FIELDS SHOULD MITIGATE ANY SEVERE WEATHER THREAT BUT
LOCALLY HEAVY RAINFALL IS POSSIBLE. BEHIND THIS SERIES OF STORM
SYSTEMS THE FAR EXTENDED FORECAST TOWARD NEXT WEEKEND LOOKS DRY AND
QUIET BUT CONSIDERABLY COLDER AS IT WILL GENUINELY FEEL LIKE
FALL...THOUGH NO FREEZING TEMPERATURES ARE ANTICIPATED AT THIS
TIME.

&&

.AVIATION...28/00Z
ISSUED AT 640 PM CDT SAT SEP 27 2014

GENERALLY CLEAR SKIES ARE EXPECTED THROUGH THE TAF PERIOD WITH
AREAS OF FOG POSSIBLE LATE TONIGHT IN RIVER VALLEYS AND OTHER LOW
LYING REGIONS. INTRODUCED MVFR FOG TO MOST TAF SITES BETWEEN 09
AND 14Z BUT OTHERWISE KEPT CONDITIONS VFR FOR THIS TAF PACKAGE.

&&

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

$$

SHORT TERM...COGIL
LONG TERM...LEE
AVIATION...SKOW



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