[LeArc] Forecast Discussion : MLI@ 1/28/03 3:45:03 AM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 280955
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
355 AM CST TUE JAN 28 2003

EVERYTHING STILL COMING TOGETHER FOR MIXED PRECIPITATION EVENT 
ACROSS FORECAST AREA TODAY. 00Z SOUNDING SHOWS VERY WARM AIR PACIFIC 
AIRMASS ABOVE H9 AFTER STRONG WARM AIR ADVECTION ALOFT OVER THE PAST 
24 HOURS. 00Z ANALYSIS SHOWED H85 THERMAL RIDGE EXTENDING NORTHEAST 
FROM 4 CORNERS WITH 5 C OVER DVN. FLOW ALOFT WAS NEARLY ZONAL WITH 
PLENTY OF MOISTURE SEEN ON WATER VAPOR IMAGERY AND UPSTREAM 
SHORTWAVE PUSHING INTO DAKOTAS. THIS WAS ALIGNED WITH ENTRANCE 
REGION OF 150KT JET AT H3. THIS WAVE WILL MOVE ALONG TIGHT 
BAROCLINIC AXIS ACROSS NORTHERN PLAINS...SENDING IT BACK SOUTH 
ACROSS FORECAST AREA TODAY. RESULTING LOW LEVEL FRONTOGENESIS AND 
STRONG UVV WILL WRING OUT PRECIPITATION OVER FORECAST AREA BY 
AFTERNOON. TIMING AND TYPE OF PRECIPITATION PRIMARY FORECAST 
CHALLENGE.

00Z ETA AND GFS HAS COME INTO CLOSER AGREEMENT THAN PREVIOUS RUNS 
WITH QPF PLACEMENT CLOSE AND ONLY MINOR DIFFERENCES IN OMEGA FIELDS 
AND FOLLOWED BLEND. Q-VECTOR CONVERGENCE...FRONTOGENESIS AND STRONG 
UPPER DIVERGENCE ALL COME TOGETHER ACROSS CWFA AROUND 15-18Z. 
CRITICAL THICKNESS VALUES INDICATE MAINLY SNOW OVER NORTHERN TIER OF 
COUNTIES...PERHAPS STARTING WITH BRIEF PERIOD OF IP OR ZR AT ONSET 
BY MID MORNING. FURTHER SOUTH...MODEL SOUNDINGS SUPPORT MIX OF SLEET 
AND ZR THIS MORNING ACROSS CENTRAL ZONES CHANGING TO SNOW AS COLD 
AIR ADVECTION INCREASES AT H85 WITH BOUNDARY SAGGING SOUTH AND 
DYNAMIC PROCESSES COOLING SATURATED LAYER. WHILE SOUTH LOOKS TO BE 
ALL RAIN AT ONSET...SURFACE TEMPERATURES WILL BE NEAR OR JUST ABOVE 
FREEZING WITH COLD GROUND TEMPERATURES CAUSING SOME ICE ACCUMULATION 
EARLY. OVERALL THINKING FROM PREVIOUS PACKAGE NOT MUCH DIFFERENT 
EXCEPT FOR LATER ONSET AND FASTER CHANGE OVER TO SNOW IN NORTH. WITH 
SIGNIFICANT ICE ACCUMULATION POSSIBLE BEFORE CHANGE OVER IN CENTRAL 
AND NORTH WILL KEEP CURRENT ADVISORY GOING WITH SNOW ACCUMULATIONS 
IN 1 TO 2 INCH RANGE. SATURATION AND LIFT ON 285K SURFACE SHIFTS TO 
SOUTHEAST OUT OF AREA EARLY EVENING AND DO NOT EXPECT ANY ADDITIONAL 
SIGNIFICANT SNOWFALL.

ANOTHER H5 SHORTWAVE PUSHES THROUGH FROM NW ON WEDNESDAY...BUT NOT 
ENOUGH MOISTURE TO SUPPORT ANYTHING MORE THAN CLOUDS. FURTHER 
OUT...STRONGER WAVE ARRIVES ON FRIDAY PRECEEDED BY WARMUP. NOT MUCH 
TIME TO DIVE INTO EXTENDED AND LITTLE CHANGES EXPECTED TO CURRENT 
GRIDS BEYOND DAY 3. 

COORDINATED WITH ARX...LOT AND ILX...THANKS.

.DVN...
IA...WINTER WEATHER ADVISORY TODAY FOR NORTHEAST AND EAST CENTRAL
IA...INDEPENDENCE AND DUBUQUE DOWN TO SIGOURNEY TO WAPELLO
IL...WINTER WEATHER ADVISORY TODAY FOR NORTHWEST IL...GENERALLY
ALONG AND NORTH OF I-80.
MO...NONE.

DLS