FXUS63 KDMX 110515 AAA
AFDDMX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1115 PM CST THU DEC 10 2009

UPDATED AVIATION DISCUSSION

.SHORT TERM /TONIGHT/...
SNOW PACK IN PLACE IS HOLDING TEMPERATURES TO THE SINGLE DIGITS OVER 
THE NORTHEAST TO 10 TO 15 DEGREES TO THE SOUTHWEST. ONE SHORT WAVE 
IS NOW ENTERING NORTHERN IOWA AND IS BRINGING A QUICK PUSH OF QG 
FORCING TO THIS REGION. POSSIBLE TO SQUEEZE A FEW FLURRIES OUT WITH 
THIS SYSTEM. ANOTHER SEGMENT OF ENERGY WILL MOVE THROUGH OVERNIGHT 
BETWEEN 06Z AND 12Z. PRIMARY IMPACT WITH THIS IS SOME MID LEVEL 
CLOUDS PASSING THROUGH. EXPECT TEMPERATURES TO DROP QUICKLY AGAIN 
TONIGHT CONSIDERING COLD TEMPERATURES THIS AFTERNOON. WEAK WARM 
ADVECTION WILL BE ONGOING EARLY IN THE PERIOD THOUGH A COLD FRONT 
WILL ACCOMPANY THE SECOND SHORT WAVE TONIGHT...BRINGING ANOTHER 
ROUND OF COLD ADVECTION. CLOUDS MAY HAVE AN IMPACT IN A FEW AREAS 
NORTH THOUGH LOWS OF 5 BELOW TO 10 BELOW SHOULD BE COMMON WITH ZERO 
TO 5 BELOW SOUTH.

.LONG TERM /FRI THROUGH THU/...
CONCERNS REMAIN SIMILAR TO WHAT THEY HAVE BEEN THE PAST FEW DAYS 
DURING THIS PERIOD...PRECIP POTENTIAL AROUND THE WEEKEND AND TEMP 
TRENDS.  FORECAST LOOKS DRY INTO EARLY SAT...HOWEVER MOST MODELS 
BRING PACIFIC WAVES INTO IA BY LATE IN THE DAY WITH MOISTURE DEPTH 
INCREASING SUFFICIENTLY FOR MEASURABLE PRECIP.  MOST LIKELY PERIOD 
FOR THIS APPEARS TO BE SAT AFTN/EVE SO HAVE TARGETED CHANCE POPS 
THERE.  PRECIP TYPE IS STILL A BIG QUESTION.  SNOW IS THE LIKELY 
P-TYPE WHEN THE COLUMN SATURATES...HOWEVER MOISTURE DEPTH IS LIMITED 
TO 1KM OR LESS AT OTHER TIMES WITH NO ICE INTRODUCTION LEADING TO 
FREEZING DRIZZLE POTENTIAL.  CONSIDERING THAT EVENT IS NEARING AND 
MODELS HAVE REMAINED AT LEAST SEMI-CONSISTENT...HAVE DECIDED TO HIT 
MENTION IN FORECAST A BIT HARDER AND ALSO MENTION IN HWO.

MODELS DIVERGE A BIT MORE HEADING INTO NEXT WEEK WITH TYPICAL 
UNCERTAINTY.  NW FLOW IN PLACE WITH FAIR AND COLD WEATHER...HOWEVER 
00Z ECMWF/GEFS AND 12Z GFS BOTH SUGGESTED A WEAK WAVE BRINGING SOME 
PRECIP POTENTIAL WED OR THU.  GOING WITH THE THINKING...IF IN DOUBT 
FAVOR THE ECMWF...SLIGHT CHANCE MENTION WAS PLACED INTO NRN PORTIONS 
THU.  HOWEVER 12Z ECMWF HAS NOW GONE DRIER...TOO LATE TO BE 
INCORPORATED INTO FORECAST...SO THIS MAY NEED TO BE ADJUSTED AGAIN 
TOMORROW DEPENDING ON FURTHER RUNS.   

HAVE HELD BACK TEMPS SOMEWHAT HEADING INTO THE WEEKEND...BUT ITS 
TOUGH TO DISCOUNT THE PERSISTENT MODEL SIGNAL OF INCREASED WARMTH 
AND MOISTURE.  SNOWPACK WILL AFFECT TEMPS SOME...BUT MOISTURE 
ADVECTION IS NOT AS INFLUENCED AS SOLAR INSOLATION ALONE SO HAVE 
CONTINUED TO NUDGE TEMPS HIGHER ALONG WITH DEWPOINTS...NOT TOO 
DISSIMILAR TO ENSEMBLE AND OPERATIONAL MOS.  BIGGER TEMP SPREAD BY 
TUE-THU HOWEVER WITH AS HIGH AS 15C H85 DIFFERENCE IN VARIOUS 
SOLUTIONS.  GEM/ECMWF ON WARM SIDE WITH GFS/GEFS COOLER.  HAVE 
PRETTY MUCH TRIED TO PLAY A COMPROMISE HERE WITH TUE THE COOLEST DAY 
AS HIGH SLIDES INTO MO VALLEY...FOLLOWED BY GRADUAL WARMING AS IT 
DEPARTS.   

&&

.AVIATION...
11/06Z...VFR CONDITIONS THRU THE TAF PERIOD. CANNOT RULE OUT A 
PASSING SNOWFLAKE OR TWO OVER NORTHERN SITES...BUT NOT ENOUGH 
SIGNIFICANCE TO MENTION IN THE TAF. COULD HAVE WRITTEN ONE 
LINERS...BUT ADDED A SECOND PREVAILING GROUP FOR WIND SHIFT TO THE 
SOUTH 21Z-23Z.

&&

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

&&

$$

SHORT TERM...DONAVON
LONG TERM...SMALL
AVIATION...MOYER