[LeArc] Forecast Discussion : MLI@ 2/22/03 3:18:30 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 222126
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
325 PM CST SAT FEB 22 2003

INTENSE CYCLONE CENTERED OVER CENTRAL KY AT 18Z HAD LARGE CLOUD 
SHIELD EXTENDING INTO EASTERN HALF IA THIS AFTERNOON. TIGHT PRESSURE 
GRADIENT BETWEEN OHIO VALLEY LOW AND ARCTIC HIGH MOVING INTO ND 
RESULTING IN INCREASING NORTHERLY FLOW WITH IMPROVING VISIBILITIES 
FROM NORTH TO SOUTH THIS AFTERNOON. 12Z UPPER ANALYSIS AND SATELLITE 
SHOWS UPSTREAM SHORTWAVE OVER WESTERN WY MOVING SOUTHEAST DOWN WEST 
COAST UPPER RIDGE. SHORT TERM CHALLENGE IS CLOUD AND RELATED 
TEMPERATURE TRENDS TONIGHT...THEN PRECIP CHANCES AS UPSTREAM WAVE 
AFFECTS SOUTH LATE SUNDAY.  

FORECAST MODELS WERE A BIT TOO AGRESSIVE WITH THE ARCTIC HIGH 
SETTLING INTO REGION...WITH MSL PRESSURE A FEW MB TOO HIGH OVER 
WESTERN IA AND EASTERN NEB. AT H85...ETA AND GFS ALSO INITIALIZED 
TEMPERATURES TOO COLD IN VICINITY OF OMA THIS MORNING. MINOR 
DIFFERENCES WITH UPSTREAM SYSTEM ALSO NOTED...WITH AGFS A BIT FASTER 
WITH Q-VEC FORCING AND OMEGA SLIGHTLY MORE NORTHERLY THAN OTHER 
SHORT TERM MODELS. WENT WITH COMPROMISE SOLUTION...KEEPING SNOW 
CHANCES IN FAR SOUTH WITH BEST CHANCE FOR MEASURABLE IN 00Z TO 06Z 
TIMEFRAME SUNDAY EVENING. DECENT UPPER DIVERGENCE DEVELOPS LATE 
AFTERNOON INTO EVENING OVER CENTRAL CWFA WITH SUFFICIENT WRAP AROUND 
MOISTURE TO SUPPORT FLURRIES AND ADDED TO ALL GRIDS FOR OVERNIGHT 
PERIOD...AS INITIALLY DRY AIRMASS WILL TAKE TIME TO SATURATE. 
PREVIOUS THINKING STILL ON TRACK WITH ACCUMULATIONS LESS THAN AN 
INCH ALONG AND SOUTH OF HIGHWAY 34. 

IN NEAR TERM...BACK EDGE OF LOW CLOUDS OVER NORTHWEST IA SHOULD 
REACH DBQ TO CID LINE BY 05Z THEN CONTINUE TO SPREAD SOUTHEAST 
OVERNIGHT. AT SAME TIME EXPECTING UPPER SYSTEM CLOUDS TO BE EAST OF 
AREA BY MIDNIGHT...RESULTING IN SOUTHEAST LAST TO CLEAR. DRY AIR 
CONTINUING TO ADVECT IN...ALONG WITH CLEARING WILL WILL SUPPORT 
SPREAD OF MINS FROM ABOUT 10 IN NORTH TO 20 IN SOUTH. CLOUDS FROM 
APPROACHING SYSTEM TO RAPIDILY OVERSPREAD AREA IN AFTERNOON. ARCTIC 
HIGH SLIDES SOUTHEAST ACROSS FORECAST AREA TUESDAY MORNING FOR 
COLDEST FORECAST PERIOD...ALTHOUGH NOT LOOKING AS INTENSE AS EARLIER 
MODEL RUNS HAD. CURRENT MINS LOOKED GOOD WITH AROUND ZERO OR A BIT 
BELOW NORTH TO NEAR 5 ABOVE SOUTH.

EXTENDED STILL INDICATES ACTIVE PATTERN WITH LONGWAVE TROUGH 
DEVELOPING OUT WEST BY MIDWEEK WITH ENERGY LIFTING NORTHEAST OVER 
UPPER MISS VALLEY LATE WEEK. MEDIUM RANGE GUIDANCE LACKING MUCH 
AGREEMENT WITH DETAILS...BUT ENOUGH CONFIDENCE AND CONSENSUS
TO KEEP SNOW CHANCES FROM WED THROUGH EARLY EARLY FRIDAY AS LEAD 
SHORTWAVE PUSHES NORTHEAST ACROSS AREA...THEN WEAKENING LONGER WAVE 
TROUGH PUSHES THROUGH.

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

$$
DLS