Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 252341
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
541 PM CST WED FEB 25 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 343 PM CST WED FEB 25 2015

INTERESTING AND VERY DIFFICULT SYSTEM TO FORECAST WILL BE PUSHING
THROUGH MUCH OF THE CWA BY 01Z AND ACROSS THE EAST BY 03Z.  MUCH OF
THE FORCING IS ALREADY EXITING...EXCEPT FOR THE EASTERN PORTION OF
THE CWA.  THE TRACK OF THE LOW SHIFTED SOME ALLOWING VERY WARM AIR
TO ENTER SOUTHWEST IOWA.  PARTS OF THE FORECAST ARE REACHED THE
UPPER 40S AND AS THE LOW SHIFTED EAST TEMPS FELL ABOUT 15 DEGREES IN
A SHORT TIME.  PTYPE WAS MIXED BUT WILL BE SWITCHING OVER TO SNOW
ACROSS THE FAR SW IN THE NEXT HOUR OR SO.  THERE IS A LOT OF
SUBSIDENCE PUSHING INTO THE AREA WHICH WILL BRING A MUCH QUICKER END
TO THE PRECIP.  HEADLINES WERE DROPPED ACROSS THE NORTH AND WEST
CENTRAL AND EXCEPT FOR THE FAR EAST...WILL BE DROPPED BY 00Z FOR
MUCH OF THE CWA.  KEPT THE ADVISORY GOING ACROSS THE SOUTHWEST TIL
00Z MAINLY FOR THE FEW OBS THAT WERE STILL REPORTING MIXED PRECIP
DURING THE EVENING COMMUTE.  I WANTED TO KEEP AWARENESS UP VERSUS A
SENSE THAT THE IMPACT OF THE PRECIP WAS OVER.

WIND CHILLS WILL NEED TO BE ADDRESSED BY THE EVENING SHIFT.  THE NW
TOUCHES ADVISORY CRITERIA LATE BUT CONFIDENCE THAT THE COLDEST AIR
WILL COME THAT FAST IS LOW.  AS A RESULT WILL LEAVE THE ADDITIONAL
HEADLINES TO THE EVENING...AFTER THE WINTER STORM HEADLINES PASS.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 343 PM CST WED FEB 25 2015

COLD HIGH PRESSURE SETTLES IN FOR THURSDAY INTO SATURDAY WITH TEMPERATURES
APPROACHING RECORD LOWS FOR THE MORNING OF THE 27TH AND 28TH. THE
COLD IS ONE FOR THE BOOKS IF NOT FOR THE FACT THAT WE HAD A MAJOR
ARCTIC OUTBREAK HOLDING THE RECORDS FROM LATE FEB INTO EARLY MARCH
OF 1962. WE MAY APPROACH SOME OF THESE...BUT NOT BREAK THEM. THE
MAIN STORM WILL THE COLD FOR THE NEXT FEW DAYS.

THE WEATHER PATTERN WILL BE ACTIVE OVER THE WEEKEND INTO NEXT WEEK WITH
TWO SYSTEMS AFFECTING THE AREA..THE FIRST WILL BE MORE OF A
NORTHWEST FLOW SYSTEM...THE SECOND A SOUTHWEST SYSTEM. SATURDAY
NIGHT IN TO SUNDAY WILL BRING LIGHT SNOWS ACROSS THE AREA...BUT
MOISTURE APPEARS TO BE LACKING FOR A LOT OF SNOW. THE PATTERN WILL
BE IN A TEMPORARY TRANSITION AS THE -PNA DEVELOPS.

THE NEXT SYSTEM WILL MOVE THROUGH THE UPPER MIDWEST WITH A SOUTHWEST
SHORT WAVE LIFTING OUT OF THE TROUGH LOCATED IN THE WEST. THAT
HAS BETTER POTENTIAL FOR HEAVIER SNOWFALL...ESPECIALLY OVER THE
EAST HALF OF THE CWA.

IN THE LONGER TERM...THE -PNA PATTERN IS MORE OF A TRANSIENT
CHANGE AND THEREFORE WILL NOT HOLD. AFTER THE DAY 7 TIME
FRAME...THE WESTERN RIDGE BECOMES MORE DOMINANT AGAIN...ALLOWING
COLD AIR TO SPILL SOUTH IN TO THE CENTRAL U.S. FOR AT LEAST THE
FIRST WEEK OR SO OF MARCH.

&&

.AVIATION...26/00Z
ISSUED AT 541 PM CST WED FEB 25 2015

WILL SEE IMPROVING AVIATION CONDITIONS DURING THIS FORECAST PERIOD
AS SYSTEM DEPARTS THE AREA. CEILINGS ALREADY IMPROVING ACROSS
NORTHERN IOWA AND WILL SEE THAT CONTINUE AS SUBSIDENCE AND DRIER
ARCTIC AIR PUSH INTO THE STATE. WILL STILL SEE IFR TO LIFR CONDITIONS
NEAR KDSM AND KOTM THIS EVENING BUT THESE CONDITIONS WILL BEGIN TO
IMPROVE BY 06Z AS PRECIPITATION ENDS WITH CEILINGS AND VSBYS
LIFTING. WITH THE DRIER AIR ARRIVING...ANTICIPATE CEILINGS TO
BECOME VFR AND GRADUALLY DISSIPATE INTO THURSDAY MORNING AS ARCTIC
HIGH PRESSURE SETTLES INTO THE PLAINS. SURFACE WINDS WILL REMAIN
FROM THE NORTH FOR THE DURATION OF THE FORECAST.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR ADAIR-
AUDUBON-CASS-CLARKE-DALLAS-DECATUR-GUTHRIE-MADISON-UNION.

WINTER STORM WARNING UNTIL 9 PM CST THIS EVENING FOR DAVIS-
JASPER-MAHASKA-MARSHALL-POWESHIEK-TAMA-WAPELLO.

WINTER WEATHER ADVISORY UNTIL 9 PM CST THIS EVENING FOR
APPANOOSE-BLACK HAWK-BREMER-GRUNDY-HARDIN-LUCAS-MARION-MONROE-
POLK-STORY-WARREN-WAYNE.

&&

$$

SHORT TERM...FAB
LONG TERM...MS FEB 15
AVIATION...COGIL


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