[LeArc] Forecast Discussion : MLI@ 7/27/02 3:26:04 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 272026 CCA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
325 PM CDT SAT JUL 27 2002

WARM FRONT AT 19Z HAD LIFTED NORTH ACROSS CWFA TO STRETCH FROM NEAR 
CHI THROUGH FAR NE IA INTO SW MN. SURFACE DEWPOINTS WELL INTO LOWER 
AND MID 70S ACROSS AREA SOUTH OF FRONT. LINE OF CU ON VISIBLE 
SATELLITE IMAGERY INDICATED SURFACE BOUNDARY FROM PIA ACROSS FAR SE 
IA TO N CENTRAL MO. THIS WAS LEFT OVER FROM EARLY MORNING MCS AND 
ALSO SITUATED ALONG EDGE OF MID LEVEL MOISTURE PLUME FROM SW CONUS 
INTO WI SEEN ON WATER VAPOR IMAGERY AND WEAK H85 CONVERGENCE. MID 
LEVEL CAP OVER AIRMASS JUST SOUTH OF FRONT KEEPING THINGS CAPPED 
ACROSS CWFA THIS AFTERNOON. AT UPPER LEVELS...STRONG SHORTWAVE WAS 
MOVING ACROSS NRN MN THIS AFTERNOON WITH UPSTREAM SHORTWAVE MOVING 
ACROSS WESTERN MT. FORECAST CHALLENGE IS THUNDERSTORM CHANCES 
TONIGHT THROUGH SUNDAY NIGHT WHEN SECOND SHORTWAVE PUSHES WESTERN ND 
COLD FRONT THROUGH CWFA.

MODELS SEEMED TO UNDERPLAY STRENGTH OF MN SHORTWAVE ASSISTING IN 
SEVERE CONVECTION THIS AFTERNOON. ETA WAS A BIT STRONGER WITH 
SOUTHERN EXTENT OF QG FORCING TO POSSIBLY IMPACT NW IL ZONES 
TONIGHT. OTHERWISE...BLEND OF ETA AND AVN GUIDANCE FOLLOWED WITH LOW 
OVERALL CONFIDENCE IN GUIDANCE QPF PLACEMENT TONIGHT WITH RELATIVELY 
POOR HANDLING OF SYSTEMS LATELY. CAP IS WEAKEST OVER NW IL AND FAR 
SRN ZONES ALONG EDGE OF H7 E-W THERMAL RIDGE. ONE AREA OF CONCERN 
TONIGHT IS NW IL WHERE WEAK QG FORCING...UPPER DIVERGENCE...AND 
PROXIMITY OF WARM FRONT MAY ALLOW CONVECTION TO INITIATE LATE 
TONIGHT...ESPECIALLY IF OUTFLOW FROM CURRENT MN CONVECTION CONTINUES 
SE. OTHER IS ALONG CURRENT BOUNDARY IN SOUTH...WHERE ALL GUIDANCE 
REDEVELOPS CONVECTION. WENT WITH 40 PERCENT POPS FOR THESE AREAS AND 
30 PERCENT ELSEWHERE FOR MAINLY LATE NIGHT CONVECTION.  ON 
SUNDAY...WILL KEEP CHANCES FOR LINGERING CONVECTION IF MCS DEVELOPS 
OVER SE HALF...OTHERWISE DRY AND HUMID WITH HIGHS IN LOWER 90S 
LOOKING REALISTIC WITH HEAT INDICES JUST BELOW ADVISORY CRITERIA. 
BETTER CHANCES FOR WIDESPREAD TSRA SUNDAY NIGHT AS SECOND STRONGER 
SHORTWAVE PUSHES COLD FRONT THROUGH AND WILL KEEP LIKELY POPS. 
SURFACE HIGH PRESSURE AND MID LEVEL NW FLOW DOMINATES MONDAY 
AFTERNOON THROUGH TUES WITH COOLER TEMPS AND LESS HUMIDITY. 

IN EXTENDED...INTRODUCED CHANCE POPS WED THROUGH FRI AS SERIES OF 
WEAK WAVES MOVE THROUGH NW FLOW AND INTERACT WITH FRONTS IN 
VICINITY. 

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

DLS