[LeArc] Forecast Discussion : MLI@ 8/28/02 2:51:28 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 280756
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
256 AM CDT WED AUG 28 2002

BLOCKING PATTERN HAS SET UP OVER CENTRAL CONUS AND PERSISTENCE TYPE 
FORECAST WILL SUFFICE THROUGH FRIDAY WITH ONLY SUBTLE TEMPERATURE 
TRENDS MAKING UP FORECAST CHALLENGE IN SHORT TERM. PATTERN SHIFT 
OVER WEEKEND INTO EARLY NEXT WEEK TURNS FOCUS TO PRECIP CHANCES IN 
EXTENDED.

HIGH PRESSURE FROM SURFACE THROUGH H7 AT 00Z CONTINUES TO CHANNEL 
WEAK EASTERLY FLOW INTO NW IL AND EASTERN IA. AT UPPER LEVELS...WEAK 
RIDGE EXTENDED FROM TX TO UPPER MISS VALLEY WITH CUTOFF LOWS 
FLANKING TO WEST...OVER SE OR...AND TO EAST OVER EASTERN KY. ALL 
SHORT TERM MODELS KEEP THIS PATTERN IN PLACE THROUGH THURSDAY BEFORE 
WESTERN CIRCULATION OPENS INTO LONG WAVE TROUGH AND SE LOW WEAKENS.

TEMPS THIS MORNING PLUNGING INTO 40S AND 50S ALREADY ACROSS LOWER MI 
UNDER INFLUENCE OF CLEAR SKY AND 1028MB HIGH. THIS AIRMASS WILL 
CONTINUE TO FEED WEST INTO FORECAST AREA. GUIDANCE HIGHS FOR TODAY 
CLOSE TO PERSISTENCE AND GOING FORECAST AND WILL NOT STRAY. AFFECT 
OF FLOW ACROSS LAKE MI WILL HAVE MORE OF AN IMPACT ON OVERNIGHT LOWS 
AS AIRMASS PICKS UP MOISTURE OFF LAKE AS SEEN BY HIGHER DEWPOINTS 
ALONG LAKE. THIS ADDED MOISTURE AND AMOUNT OF CI WILL BE MAIN PLAYER 
IN HOW LOW TEMPERATURES DROP TONIGHT AS SW-NE RIDGE AXIS STAYS OVER 
AREA. DEBRIS CI FROM UPSTREAM CONVECTION WILL CONTINUE TO AFFECT 
MAINLY WESTERN ZONES...WHILE EAST SHOULD RADIATE NICELY UNDER CLEAR 
SKIES AND SLIGHTLY WEAKER LOW LEVEL EASTERLY FLOW THAN TONIGHT. 
GUIDANCE HAS BEEN ON WARM SIDE PAST FEW NIGHTS AND LATEST RUN 
SUDDENLY MUCH COOLER WITH MAINLY 50S NORTH OF I-80. WILL DROP LOWS A 
BIT AND GO WITH MIDDLE OF ROAD WITH MID TO UPPER 50S NORTH AND 
AROUND 60 FAR SOUTH BOTH TONIGHT AND THURSDAY NIGHT. 

IN EXTENDED...MEDIUM RANGE GUIDANCE IN AGREEMENT WITH UPPER RIDGE 
FLATTENING AND ZONAL FLOW DEVELOPING OVER WEEKEND. BIGGEST 
DIFFERENCES APPEAR FROM SUNDAY AND BEYOND WITH TIMING OF NEXT TROUGH 
TO PASS TO NORTH IN ZONAL FLOW. LATEST AVN CONTINUES DRY FORECAST 
FOR SATURDAY AND WILL REMOVE PRECIP FROM SATURDAY...BUT LEAVE IN 
SUNDAY FOR NOW DUE TO LOW CONFIDENCE MODEL SOLUTIONS. POPS MAY BE 
NEEDED FOR MONDAY AND TUESDAY...BUT WILL LEAVE FOR DAY SHIFT FURTHER 
ANALYZE. 

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

DLS