[LeArc] Forecast Discussion : MLI@ 10/13/02 1:54:01 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 130700 CCA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
200 AM CDT SUN OCT 13 2002

UPPER TROUGH THAT WAS OVER WESTERN MN AND WESTERN IA ON 00Z ANALYSIS 
WAS SEEN ON SATELLITE IMAGERY PROGRESSING ACROSS MID MISSISSIPPI 
VALLEY AT 06Z. ENTIRE FORECAST AREA UNDER CLEAR SKIES WITH PRESSURE 
RISES AS HIGH PRESSURE CENTER BUILDS INTO WESTERN NEB AND KS. TREND 
OF FALLING DEWPOINTS AND GRADUALLY DECREASING NW WINDS FROM NW-SE 
SETTING STAGE FOR FROSTY START TODAY. MAIN FORECAST CHALLENGE IS 
CENTERED AROUND TEMPERATURES TODAY AND TONIGHT.

00Z GFS RUN INITIALIZED SEVERAL DEGREES C TOO COOL AT 850 MB OVER 
EASTERN IA INTO NW IL. ETA AND NGM WERE CLOSER TO REALITY AND ALL 
SHOWED THERMAL TROUGH AXIS OVER KOMA PASSING OVER CWA TODAY WITH 850 
MB WARM AIR ADVECTION COMMENCING TONIGHT. GFS COOL BIAS SHOWS UP 
THROUGH 850 MB FIELDS TODAY AND REFLECTED IN MAV HIGHS AS MUCH AS 10 
DEG COOLER THAN MET. WITH DOWNWARD VERTICAL MOTION...DEEP W-NW FLOW 
AND EXPECTED FULL SUNSHINE...SHOULD HAVE NO TROUBLE MIXING OUT TO 
850 MB. THIS WOULD RESULT IN NUMBERS CLOSEST TO FWC WITH HIGHS IN 
MID TO UPPER 50S...ALSO CLOSE TO META 2M TEMPERATURES.

TONIGHT...HIGH PUSHES SE TO A MO TO OH AXIS BY 12Z WITH TROUGH 
MOVING INTO NORTHERN PLAINS RESULTING IN BACKING LOW LEVEL FLOW OVER 
AREA TOWARD MORNING. DESPITE WARM AIR ADVECTION DEVELOPING AT 850 
MB...CLEAR SKIES AND PROXIMITY OF HIGH SHOULD RESULT IN DECOUPLING 
OF BOUNDARY LAYER AND RADIATIONAL COOLING. GUIDANCE HAS HAD SEVERAL 
RUN TREND OF INCHING MONDAY MORNING HIGHS...NOW INTO LOWER TO MID 
30S. WITH UPSTREAM AIRMASS DEWPOINTS IN LOWER 20S EXPECTED TO 
MODERATE INTO MID AND UPPER 20S...GUIDANCE LOOKS TOO WARM. WILL 
TREND NEAR OR BELOW COLDEST MOS NUMBERS AND RAISE GOING FORECAST 
ONLY SLIGHTLY TO UPPER 20S TO AROUND 30. NEED FOR A FREEZE WARNING 
WILL BE DEPENDENT ON EXTEND OF FROST/FREEZE THIS SUNDAY MORNING AND 
WILL HAVE TO DEFER DECISION TO DAY SHIFT. 

SHORTWAVE CURRENTLY IN GULF OF AK PUSHES SE MONDAY AND ROUNDS BASE 
OF NORTHERN CANADIAN VORTEX. THIS RESULTS IN SURFACE TROUGH MOVING 
INTO NORTHERN PLAINS AND RESULTING RETURN FLOW MONDAY. SW FLOW AND 
DEEP WARM ADVECTION FAVORABLE FOR SIGNIFICANT WARMUP. DEGREE OF 
WARMUP WILL BE LIMITED BY COOL MORNING START. MAV CONTINUES COOL 
BIAS AND WILL GO IN MIDDLE RANGE BETWEEN FWC AND WARM MET WITH LOWER 
TO MID 60S. LATEST GFS MEDUIM RANGE TRENDING CLOSER TO UKMO AND 
ECMWF WITH DEVELOPING ONTARIO H5 LOW FROM MID TO LATE WEEK WITH 
CYCLONIC FLOW ALOFT OVER CWA. FOLLOWING COMPROMISE UKMO AND ECMWF 
TREND WITH WEAKER UPPER TROUGH OVER AREA...WILL STAY WITH CURRENT 
PACKAGE EXTENDED TREND GOING WITH MUCH ABOVE GUIDANCE TEMPS.
CHANCES FOR PRECIP IN THU NIGHT/FRIDAY TIMEFRAME LOOKING LESS 
FAVORABLE BUT WILL ELECT NOT TO CHANGE AT THIS TIME.   

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

DLS