[LeArc] Forecast Discussion : MLI@ 8/29/02 2:30:50 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 290735
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
233 AM CDT THU AUG 29 2002

SURFACE RIDGE EXTENDING SW FROM QUEBEC INTO UPPER MISS VALLEY
CONTINUES EASTERLY FLOW OF STABLE AIR INTO FORECAST AREA. AT UPPER 
LEVELS...00Z ANALYSIS SHOWED BLOCKING PATTERN CONTINUES WITH RIDGE 
FROM TX TO WESTERN IA WITH LOWS IN W AND SE CONUS. SHORT TERM 
FORECAST CHALLENGE IS POTENTIAL FOR OVERNIGHT AND MORNING FOG AND 
LOW CLOUDS NEXT SEVERAL DAYS UNTIL PATTERN BREAKS DOWN OVER WEEKEND. 

ON WEDNESDAY...STRATUS AND AVIATION FOG LINGERED UNTIL NOON OVER 
NOON OVER MUCH OF EAST CENTRAL IA WITH CONSIDERABLE AFFECT ON MAX 
TEMPERATURES. WIDESPREAD VISIBILITIES OF 2 TO 3 MILES OVER SAME AREA 
UNDER RIDGE AXIS AT 07Z. SATELLITE IMAGERY SHOWS CONSIDERABLE CI 
FROM EARLIER CONVECTION IN WESTERN IA AND TO A LESSER DEGREE FROM 
CURRENT DECAYING MCS IN CENTRAL MN. BIGGEST DIFFERENCE FROM LAST 
NIGHT IS LACK OF FOG AND LOW CLOUDS OVER EASTERN ZONES...WHERE LOWER 
DEWPOINT AIRMASS...AROUND 55-57 F...SEEN ADVECTING NEARLY TO NW IL 
ON DAYTIME VISIBLE IMAGERY ORIGINATING FROM LAKE MI. THIS WAS 
PREVENTING OR DELAYING FOG DEVELOPMENT DESPITE CLEAR SKIES THIS 
MORNING. META HAD GOOD HANDLE ON THIS DRYER SURFACE TO H85 LAYER 
OVER N CENTRAL IL SHIFTING INTO NW IL BY 12Z. WITH IR IMAGERY 
SHOWING POTENTIAL FOR CONSIDERABLE CI NEXT FEW HOURS...DO NOT 
ANTICIPATE FOG TO WORSEN MUCH OR FOR SIGNIFICANT LOW CLOUD DECK TO 
DEVELOP THIS MORNING. CURRENT MORNING FOG WORDING SHOULD SUFFICE 
WITH SOME MENTION OF LOW CLOUDS ADDED IN MORNING. ALSO THUS DO NOT 
ANTICIPATE CONSIDERABLE CLOUD DECK TO LINGER PAST MID MORNING TO 
IMPACT TEMPERATURES. USING PERSISTENCE AND COMPENSATING FOR MORE 
SUNSHINE...MET GUIDANCE HIGHS LOOK REASONABLE.

NO CONSIDERABLE DIFFERENCES IN SHORT RANGE MODELS WITH FEATURES 
IMPACTING AREA WITH SURFACE RIDGE REMAINING IN PLACE THROUGH 
SATURDAY. DRYER AIR SHOWN BY MODELS ADVECTING IN WEAK EASTERLY FLOW 
WILL CONTINUE TO BE MODIFIED BY GROUND MOISTURE AND 
EVAPOTRANSPIRATION. THIS WILL ALLOW MORE PATCHY FOG TONIGHT AND WILL 
PUT IN ZONES. MET LOWS LOOK TOO COOL CONSIDERING ABOVE AND WILL STAY 
IN MIDDLE OF GUIDANCE RANGE AND GO FROM AROUND 57 TO 61. WILL KEEP 
SATURDAY VERY SIMILAR TO FRIDAY...BUT LEAVE OUT OVERNIGHT FOG FOR 
NOW. SURFACE RIDGE BREAKS DOWN SUNDAY WITH UPPER FLOW BECOMING 
ZONAL. LOW LEVEL RETURN SOUTHERLY FLOW DEVELOPS IN RESPONSE 
SUNDAY...BUT WITH LATEST AVN CONTINUING TREND OF KEEPING NEXT
SHORTWAVE AND FORCING WELL TO WEST...WILL REMOVE POPS.

IN EXTENDED...AVN NOW TRENDING TOWARD MORE AMPLIFIED ECMWF AND UKMET 
TROUGH THAT MOVES THROUGH WITH SURFACE COLD FRONT IN LATE 
MONDAY/EARLY TUESDAY TIME FRAME. WILL ADD MENTION OF MONDAY NIGHT 
TIME AND TUESDAY POPS. WITH SURFACE HIGH THEN BUILDING INTO GREAT 
LAKES LATE LATE TUESDAY AND WEDNESDAY FOLLOWING FROPA...GUIDANCE 
TEMPS MAY BE A BIT OPTIMISTIC AND WILL TRIM BACK SOME. 

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

DLS