[LeArc] Forecast Discussion : MLI@ 9/22/02 2:16:28 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 220721
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
221 AM CDT SUN SEP 22 2002

ENTRANCE REGION OF 130KT H3 JET EXITING NE INTO ONTARIO ALONG WITH 
HELP FROM OMEGA FROM VORT CENTER IN SW IA/NW MO ROUNDING BASE OF H5 
TROUGH PRODUCING BANDS OF MOSTLY -RA EARLY THIS MORNING OVER 
BAROCLINIC ZONE IN SE HALF OF FORECAST AREA. AS JET EXITS AND UPPER 
TROUGH AXIS SHIFTS EAST...EXPECTING MOST OF -RA TO END BY DAYBREAK. 
WILL WAIT UNTIL LAST MINUTE FOR EXTENT OF INCLUSION IN EARLY MORNING 
PERIOD IN SE ZONES. SUBSIDENT NW FLOW AND DEEP COLD AIR ADVECTION 
THEN MAIN STORY FOR TODAY WITH HIGH PRESSURE RIDGE BUILDING FROM 
HIGH PLAINS EAST INTO AREA TONIGHT. TEMPERATURES NEXT SEVERAL DAYS 
AND ASSESSMENT OF FROST POTENTIAL TONIGHT MAIN SHORT TERM CHALLENGES.

NO SIGNIFICANT INITIALIZATION PROBLEMS NOTED WITH SHORT TERM MODELS 
WITH LARGE SCALE FEATURES AFFECTING THE FORECAST AREA. BIGGEST 
FORECAST DIFFERENCE WAS AVN/S CONTINUED SHARPER AND SLIGHTLY FASTER 
MOVEMENT OF NEXT SHORTWAVE IN 42-48 HR TIMEFRAME. IMPACT ON FORECAST 
AREA IS SLIGHTLY FASTER FRONTAL TIMING WITH AVN INDICATING LOW QPF 
AMOUNTS WITH FROPA IN NORTHERN ZONES MONDAY NIGHT. ALSO...AVN BRINGS 
DOWN MORE COLDER AIR IN WAKE OF SYSTEM WITH H85 TEMPS NEAR ZERO IN 
NE IA AND MOS TEMPERATURES TOUCHING UPPER 30S IN NW. WILL STAY 
CLOSER TO MORE NORTHERLY ETA SOLUTION AND KEEP DRY FORECAST GOING.

WITH COLD ADVECTION DOMINATING THROUGH MOST OF TODAY...SHOULD HAVE 
NO TROUBLE MIXING DOWN H85 WITH HIGHS IN CLOSE TO MAV WITH NEAR 60 
NORTH TO UPPER 60S SOUTH. 20 KT H85 WINDS MIXING DOWN THIS MORNING
WILL SUPPORT FEW HOURS OF BREEZY CONDITIONS. UPSTREAM SATELLITE 
IMAGES FROM YESTERDAY AND LAPSE RATES SUPPORT SCATTERED CU. 
CONDITIONS TONIGHT WILL START OUT IDEAL FOR RADIATIONAL COOLING AS 
RIDGE MOVES INTO KS AND MO EXTENDING N INTO WI. HOWEVER...TIMING OF 
RETURN FLOW AND POSSIBLY MID LEVEL WAA CLOUDS TOWARD 12Z AS NEXT 
SHORTWAVE APPROACHES WILL BE CRITICAL. LOW END OF MOS WITH UPPER 30S 
NORTH LOOKS JUSTIFIED AND WILL KEEP MENTION OF PATCHY FROST IN 
NORTHERN ZONES. MONDAY SHOULD WARM NICELY WITH PREFRONTAL SW FLOW 
AND GOING RECOVERY INTO MID 60S TO LOWER 70S LOOKS REASONABLE. FRONT 
MOVES THROUGH EARLY EVENING...FOLLOWED BY CLEARING AND STILL LOOKS 
LIKE MONDAY NIGHT HAS POTENTIAL FOR BEING EVEN COLDER THAN TONIGHT 
AS HIGH MOVES INTO WESTERN IA BY 12Z. WILL CONTINUE TO UNDERCUT 
GUIDANCE BY SEVERAL DEGREES...BUT LEAVE FROST ASSESSMENT FOR LATER 
FORECASTS.

MEDIUM RANGE MODELS CONTINUE TO HAVE DISAGREEMENTS ON NEXT WAVE
ROTATING AROUND BASE OF CANADIAN VORTEX IN LATE WED THROUGH FRI 
TIMEFRAME AND WITH PRECIP ALREADY IN FORECAST SEE NO REASON FOR ANY 
CONSIDERABLE CHANGES TO EXTENDED AT THIS TIME.

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

DLS