[LeArc] Forecast Discussion : MLI@ 7/20/02 2:52:35 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 201952 AAA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
252 PM CDT SAT JUL 20 2002

...HIGH HEAT AND HUMIDITY MAIN CONCERNS THROUGH SUNDAY...

WARM FRONT AT MIDDAY WAS FROM FAR N CENTRAL IA CURVING SE THROUGH 
DBQ INTO N CENTRAL IL. CONVECTION NOW TRYING TO FIRE ALONG 
CONVERGENCE OF OUTFLOW FROM MN MCS OVER NORTHERN ZONES JUST SOUTH OF 
SURFACE FRONT WHERE CAP IS WEAKEST. DEWPOINTS WIDESPREAD IN MID 70S 
WITH A FEW ASOS LOCATIONS FLIRTING WITH LEGITIMATE 80 DEG READINGS 
WITH AIR TEMPS IN LOW 90S PUSHING HEAT INDEX INTO ADVISORY CRITERIA 
OF 105 IN A FEW LOCATIONS. INITIAL CHALLENGE IS SHORT TERM TSRA 
POTENTIAL FOR NORTH...THEN HOW HOT AND HUMID CONDITIONS WILL BE 
TONIGHT INTO SUNDAY. 

GUIDANCE QPF HAS BEEN POINTING TOWARD WIDESPREAD CONVECTION ACROSS 
EASTERN IA/NW IL ALL DAY...WHICH IS JUST NOW TRYING TO GET STARTED.
QUESTION IS HOW MUCH CAP WILL SUPPRESS CONVECTION AS OUTFLOW MOVES 
SOUTH INTO HIGHLY UNSTABLE BOUNDARY LAYER WITH LAPS SB CAPES OVER 6K 
J/KG. WILL CONTINUE SLIGHT CHANCES FOR NORTHEAST HALF CWA THIS 
EVENING. HOW LONG PAST SUNSET CONVECTION CONTINUES IS QUESTIONABLE 
WITH ONLY WEAK BOUNDARIES FOR CONVERGENCE AND UNIMPRESSIVE WIND 
SHEAR SO WILL KEEP EVENING WORDING FOR NOW. GUIDANCE LOWS IN MID 70S 
LOOK REASONABLE AND DEWPOINTS DO NOT DROP MUCH. DO THINK HEAT INDEX 
VALUES WILL DROP BELOW 80 DEG MINS BEFORE SUNRISE AND THUS HOLD OFF 
ON ADVISORY WORDING FOR TONIGHT.

HEAT ADVISORY IS NECESSARY FOR SUNDAY WITH TEMPERATURES WELL INTO 
MID 90S AND POSSIBLE UPPER 90S IN FAR W-NW ZONES CLOSER TO H85 WARM 
POCKET OVER NEB THAT DRIFTS NE ON SUNDAY. DEWPOINTS WILL BE SIMILAR 
IF NOT A LITTLE LOWER THAN TODAY DUE TO DEEPER MIXING INTO SLIGHTLY 
DRIER AIR ALOFT WITH SW FLOW AND SLIGHTLY LESS SURFACE MOISTURE 
POOLING WITH FRONT FURTHER NORTH. SHOULD SEE HEAT INDEX VALUES 
APPROACHING 110 IN AFTERNOON.     
 
ALL MODELS DRIVE A COLD FRONT INTO CWFA LATE SUNDAY NIGHT/EARLY 
MONDAY AS SHORTWAVE CURRENTLY MOVING ACROSS SW CANADA WI PUSHES 
THROUGH. HAVE LIMITED LIKELY POPS SUNDAY NIGHT TO NW WITH SCATTERED 
IN SE...AND THEN LIKELY ENTIRE AREA FOR MONDAY AS FRONT DRIVES 
THROUGH. HIGH PRESSURE SETTLES IN WITH DRIER NRLY SURFACE FLOW AND 
NW FLOW ALOFT TUESDAY INTO WEDNESDAY TO LIMIT HIGHS TO 80S MONDAY 
AND MAINLY IN LOWER TO MID 80S TUESDAY AND WED. MEDIUM RANGE 
GUIDANCE BRINGS WEAK SHORTWAVE THURSDAY INTO FRIDAY FOR TSRA 
CHANCES...THEN STRONGER WAVE FRIDAY NIGHT INTO SATURDAY. GUIDANCE 
TEMPERATURES LOOKED REASONABLE WITH LATE WEEK WARMING TREND.

.DVN...
IA...HEAT ADVISORY SUNDAY.
IL...HEAT ADVISORY SUNDAY.
MO...HEAT ADVISORY SUNDAY.

DLS