[LeArc] Forecast Discussion : MLI@ 2/21/03 3:27:35 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 212134
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 PM CST FRI FEB 21 2003

VISIBLE SATELLITE AND SURFACE OBSERVATIONS SHOW COLD FRONT FROM 
ABOUT KLSE TO JUST WEST OF DSM TO SOUTHWEST CORNER OF IA. DISTANCE 
TIME FEATURE HAS THIS FRONT OOZING SLOWLY SE TO REACH FAR NW CWFA 
AROUND 00Z. TO SOUTH...STUBBORN AREA OF FOG AND STRATUS OVER W 
CENTRAL IL HOLDING ITS OWN OVER LAST OF SNOW FIELDS AND EXPECT IT TO 
EXPAND SOME NORTH AND WEST AFTER SUNSET. INITIAL FORECAST CHALLENGE 
IS LOW TIMING OF CLOUDS AND FOG OVERSPREADING ENTIRE AREA TONIGHT 
AND POTENTIAL FOR -ZL AND -SN. 

SHORT TERM MODELS IN CLOSE AGREEMENT WITH ARCTIC FRONT PASSING 
THROUGH TONIGHT BEFORE GETTING WASHED OUT AND ABSORBED BY STRONGER
FRONT DEVELOPING NORTHEAST OF SURFACE LOW IN SOUTHEAST TX. WITH 
LIGHT POST FRONTAL FREEZING DRIZZLE OBSERVED THIS MORNING AND 
FORECAST SOUNDINGS LOOKING FAVORABLE FOR VERY LIGHT FREEZING DRIZZLE 
AFTER FROPA...HAVE ADDED TO MAINLY IA ZONES WITH MENTION OF FLURRIES 
AS WELL. ACROSS SOUTHEAST THIRD...ADVANCING HIGH LEVEL CLOUDS 
ASSOCIATED WITH SOUTHERN STREAM SYSTEM WILL CREATE LESS FAVORABLE 
SCENARIO FOR FREEZING DRIZZLE...BUT THINK CONDITIONS WILL BE IDEAL 
FOR EXPANSION OF CURRENT ST AND FG THAT CURRENT SHORT TERM MODELS DO 
NOT HAVE RESOLVED. COLD AIR ADVECTION BEHIND FRONT WILL IMPACT FAR 
NORTH THE MOST BY MORNING AND COLDER MAV LOOKS MORE REALISTIC. 
SATURDAY WILL SEE CONTINUED CHANCES FOR FLURRIES AS SEEN UPSTREAM 
TODAY WITH PLENTY OF CLOUDS AS H5 TROUGH MOVES OVERHEAD AND STRONG 
SURFACE LOW MOVES UP INTO OHIO VALLEY. LOW LEVELS REMAIN MOIST WITH 
SOME WEAK MID LEVEL FORCING...ESPECIALLY EARLY ON. JET LEVEL FORCING 
A BIT STRONGER WITH GOOD H3 DIVERGENCE INDICATED. 

NEXT SOUTHERN STREAM SYSTEM PASSES LATE SUNDAY TO BRING SNOW CHANCES 
FOR SUNDAY NIGHT. MODELS HAVE TRENDED WITH LIFT AND QG FORCING 
FURTHER SOUTH THIS RUN AND HAVE LIMITED POPS TO SOUTHERN 3RD CWFA 
WITH GFS INDICATING LOW TO FOLLOW SIMILAR PATH AS CURRENT SYSTEM... 
ALBEIT STARTING IN OK INSTEAD OF SE TX. LIMITED MOISTURE AND 
UNIMPRESSIVE LIFT SHOULD LIMIT ACCUMULATIONS TO LESS THAN AN INCH. 
BIGGEST IMPACT WILL BE ARCTIC HIGH THAT FOLLOWS EARLY NEXT WEEK AS 
LONGWAVE H5 TROUGH PUSHES SOUTHEAST OUT OF CANADA. MODELS HAVE 
SCALED BACK ON STRENGTH OF THIS SYSTEM WITH STRONGER SYSTEM OFF WEST 
COAST PUSHING UP DOWNSTREAM HTS OVER CENTRAL CONUS. THUS HAVE CUT 
BACK ON DEGREE OF COOL DOWN...ESPECIALLY FOR TUESDAY MORNING WHEN 
ARCTIC HIGH MOVES OVERHEAD. FURTHER OUT...GFS AND UK NOW INDICATING 
STRONGER LATE WEEK SYSTEM TO BRING POSSIBLY SIGNIFICANT SNOW CHANCES 
IN LATE WED THROUGH EARLY FRIDAY TIMEFRAME. THIS LOOKED TO BE A 
SIGNFICANT CHANGE FROM PREVIOUS RUN FOR GFS...BUT STILL WARRANTED 
CHANCE POPS.    
  
.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$

DLS