[LeArc] Forecast Discussion : MLI@ 2/15/03 3:11:29 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 152121
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 PM CST SAT FEB 15 2003

EXTENSION OF HEADLINES OVERNIGHT AND WHERE IN THE CWA THE MAIN FCST
CHALLENGE. LATEST W/V LOOP AND THIS MORNINGS UA ANALYSIS INDICATING
UPPER TROUGH AND ASSOCIATED VORT STILL SLOW TO MOVE AND HANGING
BACK...BISECTING IA FROM NORTHEAST TO SOUTHWEST. H85 LOW OVER
SOUTHWEST-SOUTH CENTRAL MO...PROGGED TO CRAWL TO WESTERN KY BY 12Z
SUN. THUS WITH ROUND OF H7-H4 THERMAL WIND ADVECTING CVA ACRS
SOUTHERN THIRD OF DVN CWA...FORCING INTO THAT AREA ON INCOMING VORT
GRADIENT OFF SOUTHEAST FLANK OF UPPER FEATURE...LINGERING H85
CONVERGENCE AND ISENTROPIC LIFT...SNOW EVENT TO CONTINUE UNTIL 07Z-
08Z OVER FAR SOUTHEAST IA...NORTHEAST MO...AND WEST CENTRAL IL.
VARIOUS SNOW PRODUCING PARAMETERS AND METHODS SUGGEST ADDITIONAL 2-4
INCHES FROM KEOSAUQUA-TO-ROSEVILLE IL ON SOUTH FROM 00Z-07Z OR SO.
MAYBE MORE IN LOCALIZED LOCATIONS FROM KAHOKA...TO MACOMB. REGIONAL
88D LOOPS INDICATE SNOW FIELD STILL EXTENDING WAY WEST INTO FAR
SOUTHEAST NE AS WELL...AND WILL EVENTUALLY MOVE THROUGH SOUTHERN
CWA. THIS INDICATES AREAS JUST SOUTH OF I-80 CORRIDOR IN LINE FOR
ADDITIONAL SNOW AS WELL...SOMETHING MODELS NOT TRENDING WITH
TONIGHT. DRYING LLVL NORTHEAST FLOW BATTLING EASTWARD PRECIP
PROPAGATION OVER THE EAST CENTRAL CWA ATTM...BUT SNOW BANDING HOLDING
TOUGH OVER FAR SOUTHERN HENRY AND BUREAU COUNTIES IN IL...WITH MORE
TRYING TO PUSH THAT WAY. THUS THESE COUNTIES MAY HAVE TO BE TAKEN
INTO ACCOUNT FOR ANY HEADLINE EXTENSION AS WELL. BIGGEST PROBLEM IS
TIGHT PRESSURE GRADIENT TO HOLD ACRS SOUTH HALF TO 2/3'S OF THE CWA
THROUGH AT LEAST MIDNIGHT...WITH RESULTANT STIFF NORTHEAST WIND TO
CONTINUE BLOWING SNOW AND REDUCED VISIBILITY TRAVEL PROBLEMS. THUS
WILL CONTINUE WINTER STORM WARNING TONIGHT GENERALLY JUST SOUTH OF
THE I-80 CORRIDOR...WITH EVENING SHIFT CHOPPING OFF NORTHERN CHUNKS
AS PRECIP SHIFTS SOUTH. SNOW MAY HANG ON ACRS FAR SOUTHEAST CWA
THROUGH 08Z-09Z THOUGH. DO WONDER IF DEVELOPING SECONDARY BAND OF
PRECIP ACRS CENTRAL MO...INTO SOUTH CENTRAL IL TO BECOME MAIN BAND
AND ROB FROM THE NORTH. THIS COMBINED WITH ONGOING STRONG...DRY AND
SUBSIDING LLVL NORTHEAST FLOW INFLUX COULD BRING ABOUT QUICKER
TERMINATION OF SNOW DEF ZONE/SHIELD OVER THE LOCAL CWA...SUGGESTING
WINTER WX ADVISORY MORE APPROPRIATE. BUT WILL HANG WITH WARNING
EXTENSION FOR NOW.

INCOMING SFC RIDGE TO BRING FAIR WEATHER FOR SUNDAY INTO MONDAY
MORNING. WILL LEAN TOWARD COOLER MAV TEMPS OVER SNOWPACK FOR
SUNDAY HIGHS...AND TAKE MAV/FWC COMPROMISE FOR MON MORNING LOWS.
RETURN FLOW TO COMMENCE ON MON...BUT WILL STILL LEAN TOWARD COOLER
MAV HIGHS TAKING SNOW COVER INTO ACCOUNT. NORTHERN STREAM SYSTEM
PUSHING ACRS UPPER MS RVR VALLEY TO DRAW SOUTHERLY FETCH OVER THE
LOCAL AREA AND HIGHS STILL MAY BREACH THE FREEZING MARK IN SOME
LOCATIONS BY LATE MONDAY AFTERNOON. LIGHT SOUTHERLY FLOW OVER MELTING
SNOWPACK MONDAY NIGHT MAY PRODUCE SOME FOG...BUT THATS THE LEAST OF
MY CONCERNS RIGHT NOW.

.LONGER RANGE(TUE-SAT)...MEDIUM RANGE MODELS GENERALLY AGREE
ON ADVERTISING SPLIT FLOW PATTERN FOR MUCH OF NEXT WEEK. NORTHERN
STREAM SYSTEM PASSING ACRS MN AND WI SHOULD DRAW WARMER TEMPS UP
OVER AREA ON TUE...BUT LINGERING SNOW COVER TO PROBABLY STILL HAVE
IMPACT AND WILL LEAN TOWARD COOLER MEX HIGHS. CWA THEN LOOKING TO
CONTINUE TO LIE IN-BETWEEN SOUTHERN AND NORTHERN STREAM FOR
GENERALLY DRY AND SEASONABLE MID WEEK. BUT BOTH UKMET AND ECMWF
SUGGEST SOUTHERN STREAM SYSTEM PULLING UP FAR ENOUGH FOR RAIN OR
SNOW TO CLIP SOUTHERN CWA LATE WED AND WED NIGHT...WHILE MRF KEEPS
PRECIP TO THE SOUTH. MAY KEEP CHANCE GOING IN THE SOUTH WITH
FAVORED UKMET/EURO BIAS. THEN MODELS HINT AT L/W PHASING BETWEEN
SOUTHERN AND NORTHERN STREAMS FOR POTENTIAL LARGE...WINDY WINTER
STORM WITH HEAVY SNOW FRIDAY AND INTO SATURDAY. PHASING AND
EVENTUAL SFC SYSTEM AND LAYOUT OF LLVL THERMAL RIBBON STORM TRACK...
OF COURSE ALL A BIG QUESTION MARK THIS FAR OUT...AND WILL GO CHANCE
OF RAIN OR SNOW SOUTH...AND SNOW NORTH HALF FOR FRI...AND ALL
SNOW CHANCE SAT CWA WIDE.


COORDINATED WITH ILX...LSX...DMX...EAX...THANX!


.DVN...
IA...WINTER STORM WARNING EXTENDED TONIGHT FOR SOUTHEAST IA.
IL...WINTER STORM WARNING EXTENDED TONIGHT FOR WEST CENTRAL IL.
MO...WINTER STORM WARNING EXTENDED TONIGHT.


$$

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