[LeArc] Forecast Discussion : MLI@ 7/19/02 3:22:38 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 192021
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
321 PM CDT FRI JUL 19 2002

SURFACE BOUNDARY AT MIDDAY INDICATED BY WEAK WIND SHIFT AXIS FROM N 
CENTRAL IL WEST BETWEEN DBQ AND DVN INTO N CENTRAL IA. DEWPOINTS 
POOLING IN LOW TO MID 70S TO SOUTH OF FRONT WITH POCKETS OF SUNSHINE 
LEADING TO DESTABILIZATION. INITIAL FORECAST CHALLENGE IS POTENTIAL 
FOR THUNDERSTORMS REFIRING TONIGHT AS FRONT DRIFTS SLOWLY SOUTH WITH 
HELP OF WAVE TOPPING RIDGE TO OUR NORTH. THEN FOCUS ON TEMPERATURES 
AND TSRA CHANCES THROUGH WEEKEND.

AVN HAD BEST HANDLE ON SURFACE FEATURES AT 18Z AND THUS FAVORED 
IN IMMEDIATE NEAR TERM. ALL MODELS SEEMED TO UNDERESTIMATE STRENGTH 
OF SHORTWAVE SEEN ON WATER VAPOR IMAGERY OVER MN SLIDING SE INTO 
CWFA THIS EVENING. BELIEVE THIS WILL AID LATE AFTERNOON DEVELOPMENT 
OF THUNDERSTORMS ALONG FRONT AND ALONG MESO BOUNDARIES ACROSS CWFA 
AND HAVE THUS GONE WITH SCATTERED POPS WITH BEST CHANCES IN SRN 
ZONES. CONVECTION SHOULD END AFTER SUNSET BEHIND FRONT IN DRIER NE 
FLOW BEHIND FRONT...WITH LINGERING CONVECTION OVERNIGHT SOUTH OF 
I-80. GUIDANCE PUSHES FRONT TO JUST TO OUR S SAT AM BEFORE IT NEARLY 
WASHES OUT. 

UPPER LEVEL WAVE OFF NW COAST PUSHES INLAND AND MOVES ACROSS 
SOUTHERN CANADA AND REINFORCES LEE TROUGH ALONG FRONT RANGE. THIS 
WILL INCREASE LOW LEVEL SW FLOW AND BRING BACK HEAT AND HUMIDITY BY 
SUNDAY. AS UPPER RIDGE FLATTENS...NEXT WEAK SHORTWAVE IN WESTERLIES 
WILL BRING TSRA CHANCES TO MAINLY NORTHERN ZONES SAT AFTERNOON. WILL 
KEEP TSRA CHANCES GOING THROUGH SAT NIGHT. BETTER CHANCES FOR TSRA 
SUNDAY AFTERNOON AND MONDAY AS SIGNIFICANT H85 LOW APPROACHES. 
CONFIDENCE NOT HIGH FOR LIKELY POPS SUNDAY NIGHT...AS BETTER FORCING 
MAY NOT ARRIVE UNTIL MONDAY. HOWEVER...WILL NOT WAVER AND KEEP 
ON-GOING LIKELY WORDING IN GRIDS. TEMPERATUREWISE...WITH 
SIGNIFICANT GROUND MOISTURE OVER MUCH OF CWFA FROM RECENT AND 
EXPECTED RAINS...HAVE DROPPED SUNDAY HIGHS A NOTCH DOWN CLOSER TO 
LATEST GUIDANCE WHICH KEEPS MID 20S C 850 MB TEMPERATURES TO WEST.

AVN MEDUIM RANGE NOW SHOWS DRY TREND WITH NW FLOW ALOFT AS H5 RIDGE 
PUSHES BACK WEST TUES AND WED AND THUS REMOVED TSRA CHANCES. LONG 
WAVE TROUGH DROPPING SE ACROSS AREA LATE WEEK WARRANTS TSRA WORDING 
FOR THURSDAY AND FRIDAY.   

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

DLS