[LeArc] Forecast Discussion : MLI@ 4/6/2003 3:51:19 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 062043
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
320 PM CDT SUN APR 6 2003

...WINTER STORM STILL TAKING SHAPE FOR TONIGHT AND MONDAY...

UPPER TROUGH WAS OVER CO/NM AT 12Z WITH 130KT H2 DIGGING THROUGH 
BASE. WATER VAPOR IMAGERY THIS AFTERNOON SHOWS MAIN SHORTWAVE 
ROTATING INTO WESTERN KS WITH MSAS SHOWING MAIN SURFACE LOW SW OF 
WICHITA. WIDESPREAD CONVECTION SEEN ON 88D MOSAIC MAINLY STAYING 
SOUTH OF H85 WARM FRONT. SO FAR SNOW CONFINED MAINLY TO DEFORMATION 
ZONE ACROSS NEB INTO WEST AND SW IA. SOME LIGHT -RA/IP HAS MADE IT 
INTO SOUTHERN ZONES THIS AFTERNOON.

MODELS CONTINUE WITH LONG ADVERTISED SCENARIO OF UPPER LOW CLOSING 
OFF TO WEST AND THEN BECOMING ELONGATED WEST TO EAST MONDAY BEFORE
PUSHING THROUGH EARLY TUESDAY. BIGGEST DIFFERENCES IN 12Z RUNS WERE 
SLOWING OF SYSTEM AND SHIFTING FORCING AND MOST PROLONGED 
PRECIPITATION EVENT TO NORTH. BIGGEST DIFFERENCE OCCURS ON 
MONDAY...WHEN GFS TAKES FOCUS OF ISENTROPIC LIFT AND DYNAMICS WELL 
TO NORTH OF FORECAST AREA. ETA HAS FOCUS ABOUT 100 MILES FURTHER 
SOUTH...WITH UKMET SPLITTING DIFFERENCE. SO FAR GFS NOT VERIFYING 
WELL..PLACING PRECIP TOO FAR NORTHEAST INTO DRY AIR. OVERALL WENT 
WITH A GFS/ETA BLEND WITH ETA PERFORMING BETTER IN SHORT TERM. 

EVERYTHING STILL COMES TOGETHER ABOUT 06Z TONIGHT...AS JET COUPLET 
BETWEEN JET OVER SW AND STRONGER JET OVER GREAT LAKES PLACES STRONG 
UPPER DIVERGENCE OVER REGION. AT SAME TIME...STRONG VORT OVER KS 
PUSHES NORTHEAST WITH STRONG QG FORCING RIGHT OVER FORECAST AREA. AT 
SAME TIME...STRONG ISENTROPIC LIFT DEVELOPS. INITIALLY WARM BOUNDARY
TEMPERATURES WILL PRODUCE MIX OF RAIN...SLEET AND SNOW IN SOUTH 
THROUGH MUCH OF EVENING...WITH BRIEF MIXTURE ACROSS CENTRAL ZONES 
THIS EVENING BEFORE CHANGE OVER INDICATED BY MODEL SOUNDINGS. 
INITIALLY WARM GROUND TEMPS AND MIXED PHASE PRECIP WILL EAT INTO 
INITIAL SNOW TOTALS AND HAVE THUS TRIMMED BACK. SNOW WILL BE HEAVY 
AT TIMES TONIGHT AND WITH STRONG DYNAMICS AND STEEP H7-H5 LAPSE 
RATES SOUTH OF INTERSTATE 80...COULD SEE SOME THUNDERSNOW...BUT WILL 
NOT BURDEN ZONES WITH WORDING AT THIS TIME. 

BEST LIFT AND MOST PROLONGED ISENTROPIC LIFT WILL FAVOR THE HIGHWAY 
20 CORRIDOR...FROM ABOUT DBQ TO INDEPENDENCE LATE TONIGHT INTO 
MONDAY MORNING AND HAVE KEPT HEAVIEST SNOWFALL AMOUNTS...6 TO 10 
INCHES THERE. ACROSS CENTRAL ZONES...EXPECT MOST OF THE SNOW TO BE 
OVER BY MID MORNING AND TRIMMED BACK TOTALS TO 5 TO 7 INCHES. ALONG 
AND SOUTH OF HIGHWAY 34...WHERE SIGNIFICANT PORTION OF PRECIP TO 
FALL AS RAIN THIS EVENING AND THEN END EARLY MONDAY...HAVE KEPT 
TOTALS IN 1 TO 3 INCH RANGE WITH ADVISORY TRIMMED BACK TO JUST 
TONIGHT. ALTHOUGH SNOW AMOUNTS LIGHT...MIXED PRECIP AND LATE SEASON
EVENT WILL WARRANT KEEPING ADVISORY. 

SLOWER DEPARTURE OF OPENING UPPER WAVE MONDAY NIGHT INTO EARLY 
TUESDAY WILL KEEP CHANCES OF LIGHT SNOW GOING AS ANOTHER ALBEIT 
WEAKER VORT ROTATES OVER AREA AND RAISED POPS SOME WITH FLURRIES 
INTRODUCED TUESDAY MORNING. SHOULD THEN CLEAR TUESDAY AS SURFACE 
HIGH MOVES INTO AREA. FRESH SNOW COVER AND NORTH FLOW TO KEEP TEMPS 
IN MAINLY 30S TUESDAY...THEN SET STAGE FOR TEENS WEDNESDAY MORNING 
AND WENT JUST BELOW COLDER MAV GUIDANCE. 

IN EXTENDED...SNOW COVER TO TEMPER MID WEEK WARMING TREND AND STAYED 
A FEW DEGREES BELOW GUIDANCE THROUGH THURSDAY. STRONG RETURN FLOW 
WILL EAT AWAY MOST OF SNOW COVER BY FRIDAY AND THUS SHOULD SEE 60S. 
KEPT THUNDERSTORM CHANCES IN SATURDAY AS WEAK FRONT PUSHES THROUGH 
AND STAYED CLOSE TO GUIDANCE WITH WEEKEND TEMPERATURES.    

COORDINATED WITH ILX...THANKS.

.DVN...
IA...WINTER STORM WARNING TONIGHT THROUGH MONDAY...ROUGHLY NORTH OF 
A LINE FROM FAIRFIELD TO BURLINGTON.
...WINTER WEATHER ADVISORY TONIGHT...ALONG AND SOUTH OF ABOVE LINE.
IL...WINTER STORM WARNING TONIGHT THROUGH MONDAY...ROUGHLY ALONG AND 
NORTH OF A LINE FROM KEITHSBURG TO PRINCETON.
...WINTER WEATHER ADVISORY TONIGHT...SOUTH OF ABOVE LINE.
MO...WINTER WEATHER ADVISORY TONIGHT...

$$

DLS