FXUS63 KDMX 092324 AAA
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
522 PM CST WED DEC 9 2009

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
THE STORM SYSTEM IS DEPARTING BUT WE WILL STILL HAVE SOME HEADLINES 
OUT FOR VARIOUS CONDITIONS.  THE WIND WILL BE RATHER BRISK THIS 
EVENING EVEN AFTER DIMINISHING BY 10 PM. BLOWING SNOW IS STILL 
LIKELY AND RURAL AREAS MAY STILL HAVE REDUCED VISIBILITIES THIS 
EVENING SO I DECIDED TO GO WITH A WINTER WEATHER ADVISORY TO COVER 
THE COMBINATION OF BLOWING SNOW AND BITTER COLD WIND CHILLS AS 
STRONG COLD ADVECTION CONTINUES TO POUR INTO CENTRAL IOWA.  
OVERNIGHT I EXPECT THE WIND TO DIMINISH ENOUGH SO THAT BLOWING SNOW 
WILL NOT BE ENOUGH TO REDUCE VISIBILITIES TO CRITICAL LEVELS BUT 
WIND CHILLS WILL CONTINUE TO PLUMMET TO 20 TO 30 BELOW OVER THE CWA. 
AS A RESULT WE WILL GO WITH A WIND CHILL ADVISORY OVERNIGHT AS THE 
MAIN THREAT SHIFTS.  WIND CHILLS ARE NOT EXPECTED TO IMPROVE UNTIL 
MID MORNING THURSDAY SO THE WIND CHILL ADVISORY WILL REMAIN IN 
EFFECT UNTIL 10/15Z.

.LONG TERM /THU THROUGH WED/...
LITTLE WX OF CONCERN THROUGH THE REMAINDER OF THE WORK WEEK OUTSIDE 
OF TEMPS.  BROAD LONG WAVE TROUGH REMAINS ENTRENCHED THROUGH MUCH OF 
NRN CONUS WITH SFC HIGH PRESSURE CROSSING SRN PLAINS.  WITH DEEP 
SNOW PACK AND TEMPS MUCH BELOW NORMAL...GUIDANCE WILL STRUGGLE TO 
CAPTURE DEGREE OF COOLING SO HAVE GENERALLY GONE BELOW MOS MUCH AS 
ALREADY DEPICTED IN GOING FORECAST. 

PRIMARY CONCERN HEADING INTO THE WEEKEND INVOLVES MAGNITUDE OF 
WARM UP AND POTENTIAL TRANSIENT SYSTEM AROUND SUNDAY.  NO 
SOLUTION SEEMS TO STICK OUT AS BEING ANY MORE FAVORABLE AT THE 
MOMENT SO HAVE PRETTY MUCH BLENDED PREVIOUS FORECAST WITH LATEST 
DETERMINISTIC AND ENSEMBLE SOLUTIONS.  MODELS ARE NOW MUCH MORE 
AGGRESSIVE PUSHING WARMTH AND LOW LEVEL MOISTURE NORTHWARD AHEAD OF 
SUNDAY WAVE.  MODEL CHANGES ARE EXTREME...AND HAVE NOT GONE AS WARM 
AS RAW MODEL TEMPS/DEWPOINTS SUGGEST...BUT HAVE LEANED IN THAT 
DIRECTION WARMING TEMPS FOR EARLY NEXT WEEK.  THIS INCREASED WARMTH 
AND MOISTURE OVER THE SNOW COVER WILL LIKELY LEAD TO STRATUS AND/OR 
FOG AT THE LEAST...AND POSSIBLY SOME FREEZING DRIZZLE OR FREEZING 
RAIN.  MOST LIKELY PERIOD FOR MEASURABLE PRECIP SEEMS TO BE SUN 
NIGHT RIGHT NOW SO HAVE RAISED TO CHANCE POPS WITH SNOW AND FREEZING 
DRIZZLE MENTION.  ADDITIONAL PERIODS OF FREEZING DRIZZLE WORDING MAY 
ALSO BE NEEDED AS THE EVENT NEARS.

&&

.AVIATION...
10/00Z...LOWER CLOUDS AND LIGHT SNOW OVER KMCW...KALO AND KOTM WILL 
QUICKLY SHIFT EAST BY 02Z. IN ADDITION...NW WINDS WILL BE 
DIMINISHING WITH LOSS OF MIXING. SO EXPECT IMPROVING CONDITIONS AT 
SITES STILL EXPERIENCING MVFR TO IFR CONDITIONS THIS EVENING. VFR 
CONDITIONS TO FOLLOW FOR THE REMAINDER OF THE TAF PERIOD. 

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING CONTINUES THROUGH 00Z...WINTER WX ADVY FOR BLOWING 
SNOW AND WIND CHILLS 00Z-06Z...WIND CHILL ADVY 06Z-15Z...ALL FOR 
ENTIRE FORECAST AREA.

&&

$$

SHORT TERM...FAB
LONG TERM...BSS
AVIATION...MOYER