[LeArc] Forecast Discussion : MLI@ 3/5/03 2:33:47 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 050843
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
240 AM CST WED MAR 5 2003

COLD FRONT SNAKING FROM CENTRAL IN THROUGH ST LOUIS INTO EASTERN TX WITH
IMPRESSIVE THERMAL GRADIENT OF SOME 40 DEGS OVER 100 MI. UPPER TROUGH 
AXIS EXTENDS FROM NORTHERN PLAINS TO SOUTHERN CAL. LARGE SCALE CONFLUENCE 
OF UPPER FLOW BETWEEN NORTHERN/SOUTHERN SPLIT OVER REGION.
VIGOROUS H3 JET FROM QUEBEC CAN TO GREAT LAKES...WITH SOUTHERN JET EXTENDING
FROM SOUTHERN PLAINS THROUGH TENNESSEE VALLEY. COUPLING RESPONSIBLE
FOR STRONG LIFT LAST EVENING RESULTING IN MOD-HVY SNOW OVER MUCH OF THE
REGION. SNOW AMOUNTS GENERALLY RUNNING IN THE RANGE OF 4-8 IN WITH
LESSER AMOUNTS IN SOME LOCATIONS SOUTH/EAST. SNOW GRADUALLY DIMINISHING WITH
BACK EDGE EAST OF FREEPORT TO IOWA CITY LINE AT 08Z. SATELLITE SHOWS
EXTENSIVE MID/HIGH CLOUDINESS ALL THE WAY BACK INTO SOUTHEAST MN AND NORTHWEST 
IA.

MAIN FORECAST CHALLENGE REVOLVES AROUND TEMPS NEXT SEVERAL DAYS WITH IMPACTS
FROM FRESH SNOW COVER. ASSESSING MEASURABLE PCPN POTENTIAL 
ALSO OF CONCERN NEXT FEW DAYS WITH SEVERAL WEAK WAVES ZIPPING THROUGH IN ZONAL 
UPPER FLOW. 

SHORT TERM...WILL MONITOR RADAR TRENDS FOR FIRST PERIOD WORDING. DEFORMATION
ZONE COMING THROUGH QUAD CITIES ATTIM IS PROGGED TO WEAKEN...WHICH
RADAR TRENDS SUPPORT. SEVERAL WAVES TO EJECT FROM BASE OF TROUGH IN SOUTHERN
CAL. NEXT WAVE LIFTING FROM KS INTO NORTHERN MO RESPONSIBLE 
FOR DEVELOPMENT OF CONVECTIVE RETURNS STREAKING EAST ACROSS CENTRAL MO.
EXTRAPOLATION TAKES MOST OF THIS ACTIVITY JUST SOUTH OF CWA. 
BASED ON WEAKENING DEFORMATION ZONE...PLAN TO LET WARNING EXPIRE.
NOT EXPECTING MUCH MORE ADDITIONAL ACCUMS. STILL EXPECT AREAS OF BLOWING AND
DRIFTING WITH NORTH WINDS IN 10-20 MPH RANGE. ANOTHER WEAK WAVE WILL BE
PASSING JUST SOUTH AND CLOSE ENOUGH THAT WE COULD SEE AFTERNOON FLURRIES IN THE
SOUTH. OTHERWISE...EXPECT CONSIDERABLE MID/HIGH CLOUDS WITH UPPER TROUGH
STILL HOLDING BACK TO THE WEST TODAY...WITH SOME THINNING OF THE 
CLOUDS POSSIBLE NORTH. TEMPS WILL STRUGGLE WITH FRESH SNOW COVER AND WILL
TRIM COUPLE DEGS FROM GUIDANCE.  

TONIGHT/THURSDAY...STRONG WARM ADVECTION COMMENCES...AS SURFACE RIDGE SHIFTS
EAST. TEMPS WILL BE QUITE TRICKY WITH POTENTIAL FOR PARTIAL CLEARING
SOME AREAS BEFORE ADDITIONAL MID CLOUD BAND SWINGS THROUGH.
WILL NOT GO MORE THAN FEW DEGS OR 1 CAT OR SO BELOW GUIDANCE DUE TO EXPECTED
CLOUD COVER. NEXT QUESTION IS PCPN POTENTIAL WITH WARM ADVECTION.  
SHOT OF MID LEVEL FORCING SWINGS THROUGH TONIGHT...BUT LOW LEVELS DRY AND IT
APPEARS AS THOUGH LIFT AND WHAT MOISTURE AVAILABLE IS OUT OF PHASE.
STILL THOUGH CAN/T RULE OUT FEW FLURRIES WITH VORT MAX AND PVA. WILL HOLD OFF 
ON LOW CHANCE POPS ATTIM DUE TO THE LACK OF MOISTURE. BULK OF WARM 
ADVECTION EXPECTED TO ARRIVE THU AFTERNOON. FRESH SNOW COVER THOUGH TO CUT INTO
WARMUP POTENTIAL NOT ONLY THU BUT INTO SAT. FMR GUIDANCE STILL TRYING TO PIN
50 DEGS ON US FRI-SAT. UNFORTUNATELY WON/T HAPPEN. WILL GENERALLY STAY BELOW 
GUIDANCE THROUGH PERIOD. DUE TO STRONG MARCH SUN THOUGH WILL ONLY GO 
BELOW BY CAT OR SO. 

NEXT PCPN POTENTIAL APPEARS FRI WITH FRONT SAGGING DOWN FROM THE NORTH.
MOISTURE LIMITED...SO ANY PCPN VERY LIGHT. 

WON/T MAKE MANY CHANGES TO EXTENDED ATTIM DUE TO TIME CONSTRAINTS. 
LOOKS LIKE 

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

$$

05