[LeArc] Forecast Discussion : MLI@ 12/6/02 2:41:18 PM

[Richard R. Sample]

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


FXUS63 KDVN 062055
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
252 PM CST FRI DEC 6 2002

LOW LEVEL WARM AIR ADVECTION HAS BOOSTED TEMPERATURES INTO 30S THIS 
AFTERNOON OVER ALL BUT FAR NORTHERN ZONES WHERE VISIBLE IMAGERY 
CLEARLY SHOWS LINGERING SNOW COVER. AT SURFACE...18Z ANALYSIS SHOWED
RIDGE OVER OHIO RIVER VALLEY AND TROUGH EXTENDING SW OUT OF HUDSON 
BAY AREA INTO NEB PANHANDLE. IMPRESSIVE MID LEVEL SHORTWAVE SEEN ON 
WATER VAPOR IMAGERY MOVING INTO SW MN RESULTING IN ONLY MID AND HIGH 
LEVEL CLOUD DECK THAT WILL BRUSH THROUGH CWA THIS EVENING. FORECAST 
CHALLENGE IN SHORT TERM IS TEMPERATURES THROUGH WEEKEND AS NW FLOW 
REGIME CONTINUES. 

SHORTWAVE MOVING INTO MN WAS APPRECIABLY FASTER THAN MODEL SOLUTIONS 
THIS MORNING. THIS WILL ONLY AFFECT TIMING OF CLOUDS THIS 
EVENING...OTHERWISE LITTLE SIGNIFICANT DIFFERENCES NOTED IN MODELS 
AND BLEND OF GFS/ETA USED. BRIEF PERIOD OF THIN CLOUDS WILL COVER 
NORTHERN ZONES THIS EVENING...THEN CLEARING SKIES UNDER WEAK 
SUBSIDENCE. AT SURFACE...RATHER DIFFUSE TROUGH OVER SD AND NEB 
PUSHES EAST ACROSS AREA TONIGHT WILL BE ENOUGH TO KEEP LOW LEVELS 
FROM DECOUPLING MUCH AND PREVENT TEMPERATURE PLUNGE. META HAS GOOD 
HANDLE ON 2M TEMPERATURES TODAY AND LOWS AROUND 12Z IN 20S LOOKS 
GOOD AND WITHIN RANGE OF MOS NUMBERS. MADE SOME MINOR ADJUSTMENT FOR 
SNOW AREAS IN NORTH FOR BOTH LOWS TONIGHT AND HIGHS SATURDAY. MORE 
NEUTRAL ADVECTION AT H85 DEVELOPS SATURDAY AS HUDSON BAY VORTEX 
BEGINS TO SHIFT E-SE. RESULT WILL BE STRONGER NORTH TO SOUTH 
TEMPERATURE RANGE ACROSS FORECAST AREA SATURDAY AND AGAIN FOLLOWED 
META 2M WITH AROUND 32 NORTH...WELL BELOW MOS...TO MID 40S FAR 
SOUTH. COLD FRONT BRINGS REINFORCING SHOT OF COLD AIR EARLY 
SUNDAY...FOLLOWED BY HIGH MOVING OVERHEAD SUNDAY NIGHT. WITH DRY 
AIRMASS AND LITTLE MID LEVEL SUPPORT...WILL BE A DRY FROPA. UPSHOT 
WILL BE HIGHS ONLY IN 20S SUNDAY...THEN ANOTHER NIGHT IN SINGLE 
DIGITS NOT FAR FROM GFS GUIDANCE.

IN EXTENDED...GFS STILL POINTING TOWARD PRECIP EVENT IN THURSDAY 
INTO FRIDAY TIMEFRAME AS UPPER LOW DEVELOPS IN ACTIVE SOUTHERN 
STREAM. THIS IS AFTER WESTERN RIDGE BREAKS DOWN EARLY WEEK AND FLOW 
BECOMES MORE ZONAL. GFS HAS BEEN TRENDING TOWARD POSSIBLE SNOW EVENT 
THURSDAY FOR SEVERAL DAYS NOW AND LATEST UK STARTING TO BACK GFS 
SOLUTION ALBEIT WITH MUCH WEAKER UPPER LOW 12Z THU. NOT A HIGH 
CONFIDENCE EVENT THAT FAR OUT...BUT WILL JUMP ON MODEL TREND AND  
WITH THERMAL PROFILES INDICATING MAINLY SNOW HAVE AND ADDED CHANCES 
FOR THURSDAY AND FRIDAY. OTHERWISE...CONTINUED WITH MAINLY ABOVE 
GUIDANCE HIGHS THROUGH MID WEEK.  

IA...NONE.
IL...NONE.
MO...NONE.

DLS