[LeArc] Forecast Discussion : MLI@ 9/20/02 2:31:41 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 200739
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
239 AM CDT FRI SEP 20 2002

UPPER ANALYSIS AT 00Z SHOWED CIRCULATION JUST WEST OF OMA INSIDE 
LONG WAVE EXTENDING FROM WESTERN LAKE SUPERIOR TO WEST TEXAS. 120KT 
H250 JET EAST OF TROUGH FROM SE KS TO EASTERN IA AND HEIGHT FALLS 
ACROSS EASTERN KS TO NE TEXAS INDICATING SYSTEM SHOULD QUICKLY FILL 
AND PROGRESS NE AS MODELS ADVERTISE. SIGNIFICANT H5 HEIGHT FALLS 
INDICATED WITH DEEPENING TROUGH OVER WESTERN CANADA SEEN DIVING SE 
ON SATELLITE WV IMAGERY. AT SURFACE...COLD FRONT MOVING THROUGH 
EASTERN IA WITH WIDESPREAD AND MAINLY POST FRONTAL SHOWERS W OF MISS 
RIVER. FORECAST CHALLENGE IS POPS IN FIRST PERIOD AS SHOWERS 
LINGER...THEN TEMPERATURES THROUGH WEEKEND AS SECONDARY COLD FRONT 
ASSOCIATED WITH CANADIAN WAVE SWEEPS THROUGH.

NO SIGNIFICANT INITIALIZATION PROBLEMS NOTED WITH 00Z MODELS. SOME 
DIFFERENCES APPEAR WITH PROGRESSION OF UPPER TROUGH AND SURFACE 
FRONT. AT 06Z...AVN HAD BEST HANDLE ON SURFACE FRONT AND ONLY MODEL 
TO PICK UP LOW ALONG FRONT MOVING NE ACROSS EASTERN IA AND 
GENERALLY FOLLOWED FOR SHORT TERM. NGM...AND TO SOME DEGREE 
ETA...WERE TOO FAR W WITH THE FRONT. SHOWERS AND ISOLATED 
THUNDERSTORMS SEEN ON 88DS OVER SW IL AND EASTERN MO WILL SPREAD NE 
INTO NW IL ZONES BY SUNRISE AND CONTINUE THROUGH MORNING WITH HELP 
OF UPPER JET ENTRANCE REGION AND MID LEVEL DYNAMICS. WILL INCREASE 
POPS TO LIKELY FOR IL ZONES AND KEEP HIGH SCATTERED GOING FOR MO AND 
IA ZONES TODAY...FOR MAINLY MORNING SHOWERS. BOTH ETA AND AVN AGREE 
WITH FRONT PUSHING EAST OF CWA BY 18Z WITH SOME MID LEVEL FORCING 
INTO EARLY AFTERNOON BEFORE MID LEVEL TROUGH PUSHES EAST BY 00Z. 
CLOUDS AND SHOWERS TO LIMIT MUCH WARMING TODAY...BUT WITH WARM 
START...WENT ALONG WITH BLEND OF MOS GUIDANCE THAT WAS CLOSE TO 
GOING GRIDS WITH UPPER 60S NORTH TO NEAR 75 SE. 

CANADIAN H5 WAVE DIVING SE TONIGHT PUSHES SECONDARY COLD FRONT 
THROUGH CWA BY MORNING. VERY DRY UPSTREAM AIRMASS SHOULD ALLOW 
TEMPERATURES DROP...BUT AMOUNT OF COOLING WILL DEPEND ON HOW 
FAST CLOUDS CLEAR OUT IN EVENING. GUIDANCE LOWS LOOK TOO WARM AND 
WILL LOWER CLOSER TO COLDEST MET VALUES WITH MID 40S NW TO LOWER 50S 
SE. SAT AND SUN WILL BE MOSTLY SUNNY AND SEASONABLY COOL WITH E-W 
SURFACE RIDGE AND UPPER LEVEL LONG WAVE TROUGH OVER AREA AND LITTLE 
CHANGE TO CURRENT TEMPERATURES EXPECTED. 

IN EXTENDED...FALL WEATHER STILL ON TRACK NEXT WEEK WITH NEXT 
SHORTWAVE IN NW FLOW TO PUSH NEXT COLD FRONT THROUGH AND WARRANT 
MENTION OF UPPER 30S LOWS ACROSS NORTH TUESDAY MORNING. NO 
SIGNIFICANT DIFFERENCES IN MEDIUM RANGE GUIDANCE AND DO NOT EXPECT 
ANY CONSIDERABLE CHANGES TO EXTENDED.

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

DLS