FXUS63 KDMX 141735 AAA
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1137 AM CST MON DEC 14 2009

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TODAY/...
SFC LO HAS MOVED TO JUST SW OF KMKC AND LOOKS TO BE ABOUT ON TRACK.  
ONCE CENTER PASSES THE COLD AIR WILL SINK SOUTH AND CHNG THE 
FREEZING PCPN OVER TO -SN.  HRRR RUNS SEEMED TO HAVE A PRETTY GUD 
HANDLE ON THE CHANGE OVER.  SERN IA HAS DROPPED TO <1/4 IN FG THIS 
MRNG AND WILL ISSUE A SHORT TERM ADVY FOR THAT AREA FOR FOG.  FEEL 
TEMPS WILL REMAIN WARM ENOUGH THERE TO PREVENT THE ICING PROBLEMS OF 
FARTHER NW.  WITH MAIN ADVY...KEPT THAT GOING THROUGH 15Z.  FEEL 
SUPPORT WILL DIMINISH BY THEN AS S/WV PASSES AND WILL BE JUST A 
FLURRY STTN WITH SOME BLWG AND DRFTG FOR A WHILE.  TEMPS FALLING 
THRU THE DAY WITH HIGH TEMPS AT 12Z.  AS FAR AS SNOW AMOUNTS...DO 
NOT EXPECT TO SEE MUCH ACCUM WITH TTLS GENLY UNDER AN INCH IN THE 
SERN PART OF THE ADVY AREA...AND NOT MUCH MORE THAN IN INCH IN THE 
NW.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
MONDAY NIGHT INTO WEDNESDAY STILL LOOKS QUIET AND COLD AS A 
REINFORCING SHOT OF COLD AIR...COURTESY OF A MID-LEVEL SHORTWAVE AND 
SURFACE ARCTIC HIGH...MOVES THROUGH IN THE NORTHWESTERLY FLOW. 
RAISED MIN TEMPS A FEW DEGREES TUESDAY NIGHT AS IT APPEARS LIGHT 
SOUTHERLY WINDS AND SOME MID/HIGH CLOUDS MAY INHIBIT RADIATIONAL 
COOLING SOMEWHAT. WIND CHILL ADVISORY APPEARS POSSIBLE LATE TONIGHT 
ACROSS THE NORTH...ROUGHLY ALONG THE NORTH OF HIGHWAY 30. HOWEVER 
GIVEN THE LIGHT NATURE OF THE WIND THE PROJECTED WIND CHILL VALUES 
OF -20 TO -25 WILL BE PRIMARILY DUE TO COLD TEMPS RATHER THAN WHAT 
IS NORMALLY THOUGHT OF AS WIND CHILL...AND THERE IS A POSSIBILITY 
THAT THE WIND SPEED FORECAST COULD DROP FURTHER WHICH WOULD BRING 
THESE VALUES TO -20 OR ABOVE. GIVEN THE MARGINAL NATURE OF THIS 
POTENTIAL HAZARD AND THE FACT THAT WE ALREADY HAVE TWO ADVISORIES 
OUT THIS MORNING...WILL HOLD OFF ON ANY WIND CHILL ADVISORY FOR NOW 
AND ALLOW THE DAY SHIFT TO REASSESS THIS AFTERNOON.

BY WEDNESDAY MORNING THE SURFACE HIGH WILL HAVE MOVED BY WITH 
SOUTHERLY FLOW KICKING IN BENEATH RIDGING ALOFT...LEADING TO A 
STEADY WARMING TREND FOR A COUPLE OF DAYS. LONG RANGE MODELS 
CONTINUE TO INDICATE ONE OR MORE SHORTWAVES MOVING THROUGH THE FLOW 
LATER IN THE WEEK BRINGING A RETURN OF PRECIP CHANCES...HOWEVER 
THEIR SOLUTIONS ARE WIDELY VARIED IN TERMS OF THE 
TIMING...NUMBER...AND LOCATION OF SUCH WAVES. THE 00Z GFS AND GEM 
SEEM TO HAVE A PRETTY GOOD HANDLE ON THE SITUATION...ALTHOUGH GFS 
APPEARS A BIT FAST...WITH TWO OR THREE WAVES MOVING THROUGH IN QUICK 
SUCCESSION BETWEEN THURSDAY NIGHT AND FRIDAY NIGHT. FORECAST 
SOUNDINGS SUPPORT SNOW AS THE PRECIP MODE DURING THIS 
TIME...ALTHOUGH GFS IS ONLY JUST BELOW FREEZING IN THE LOWER LEVELS. 
HAVE KEPT SLIGHT AND LOW CHANCE POPS IN THE FORECAST FOR THIS PERIOD.

&&

.AVIATION...
14/18Z...SFC LOW OVER NORTHERN ILLINOIS WILL QUICKLY PULL EAST WITH 
PRECIPITATION ENDING QUICKLY ACRS THE FORECAST AREA EARLY THIS 
AFTERNOON.  MVFR TO VFR CIGS WILL PERSIST FOR MUCH OF THE 
AFTERNOON...BUT INCREASING SUBSIDENCE BY TONIGHT SHOULD ALLOW FOR 
CLEARING AND WIDESPREAD VFR CONDITIONS OVERNIGHT INTO TUESDAY.  SFC 
WINDS WILL BE STRONG FROM THE NORTHWEST BUT WILL WEAKEN OVERNIGHT AS 
PRESSURE GRADIENT RELAXES.

&&

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

&&

$$

SHORT TERM...MS DEC 09
LONG TERM...LEE
AVIATION...COGIL