[LeArc] Forecast Discussion : MLI@ 11/23/02 3:14:36 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 232126
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
320 PM CST SAT NOV 23 2002

ACCUMULATING SNOW LIKELY FOR MUCH OF AREA SUN AFTN/NGT...WITH MAIN CONCERN
AMOUNTS AND WHETHER ANY HEADLINES NEEDED. 

INITIAL WIND SHIFT WHICH SWEPT ACROSS REGION THIS MORNING NOW WELL SOUTH...
WITH MAIN THRUST OF COLD AIR NOW SAGGING SOUTH THROUGH UPPER MIDWEST
ON HEELS OF ARCTIC FRONT WHICH EXTENDS FROM ROUGHLY JUST SOUTH OF LINE DLH TO
JMS. CHECK OF RADARS AND SURFACE OBS SHOW SN ACROSS NORTHERN 
ROCKIES INTO PORTIONS OF NORTHERN PLAINS AHEAD OF IDAHO SHORTWAVE WITH
FAVORABLE JET DYNAMICS. NOT MUCH APPEARS TO BE MAKING IT TO GROUND IN SOUTHEAST
SD ALTHOUGH RAP HAS REPORTED SN. SN ALSO OCCURING BEHIND ARCTIC 
FRONT WITH SOME BLSN AND SHSN.  

OVERALL...NGM AND ETA COMING MORE IN LINE WITH "WETTER" AVN/GFS WITH
SYSTEM SUN AFTN/NGT. UPPER PATTERN ALLOWS COLD CANADIAN HIGH TO BUILD SOUTH
INTO PLAINS AND UPPER MIDWEST NEXT 24 HRS...WITH SHORTWAVE SHEARING
EASTWARD IN CONFLUENT FLOW. OVERRUNNING SETUP DEVELOPS OVER SHARP BAROCLINIC 
ZONE ON SUN WITH LIFT INCREASING 18Z AND PEAKING WITHIN A FEW HOURS AROUND
00Z. WILL BE INCREASING POPS TO LIKELY ALL AREAS...AND NEXT SHIFT 
MAY NEED TO CONSIDER CATEGORICAL ESP CENTRAL AND SOUTH IF THINGS CONTINUE
TO TREND WITH 12Z RUNS. FOCUS THEN TURNS TO AMOUNTS...AND BIG FACTOR TO
CONSIDER IS BOUNDARY LAYER TEMPS CENTRAL AND SOUTH. INITIALLY PCPN COULD START
OUT AS RAIN OR RAIN/SNOW MIX IN SOUTH BUT IT SHOULD CHANGE QUICKLY TO
SNOW WITH LIFT AND EVAPORATIVE COOLING PROCESSES. WITH WINDS STAYING UP AND
CLOUDS WILL GO A BIT ABOVE GUIDANCE ON MINS TONIGHT. SO...GOING WITH
A WARMER START...THINK M/U 30S CENTRAL TO SOUTH WITH EVEN A 40 DEG READING
NOT OUT OF QUESTION FAR SOUTH. THIS POSES PROBLEM WITH AMOUNTS AS
INITIALLY EXPECT MELT...BUT RATE SHOULD INCREASE TO WHERE WE COULD SEE
QUICK COUPLE 2-3 HOURS OR SO OF DECENT SNOW...WHICH WOULD ACCUMULATE REGARDLESS
OF TEMPS. BULK OF ACCUMULATION EXPECTED AFTER DARK AS WELL. 
STILL HAVE BIG MODEL DISCREPANCIES ON WHERE HEAVIEST QPF WILL OCCUR AS
CONCEPTUALLY SUGGESTS SOUTHEAST 1/3RD OR SO. FRONTOGENETICAL FORCING AND
RIGHT REAR OF H25 JET WITH BULLSEYE SOUTH/EAST. WILL BROADBRUSH GENERAL 1-3
INCH AMOUNTS ALONG AND SOUTH OF I-80...THOUGH CAN SEE MAYBE AROUND 1 INCH
FAR SOUTH WHERE IT WILL BE WARMEST. FURTHER NORTH AMOUNTS TAPERING
TO AROUND 1 INCH AS WELL. HOLD OFF ON ADVISORY ATTIM...DUE TO UNCERTAINTY.

TEMPS WILL BE A CHALLENGE. LATEST RUNS CONTINUE TO WARM A FEW DEGS.
SEEMS LIKE THAT/S BEEN THE TREND THIS FALL...SO WILL GENERALLY SIDE TOWARD
WARMER GUIDANCE THROUGHOUT MAKING NECESSARY ADJUSTMENTS. 

NEXT SYSTEM DIVING SOUTH IN NORTHWEST FLOW LATE MON/TUE...WITH CONTINUED
MODEL DIFFERENCES. ALTHOUGH...12Z ETA LOOKING SIMILAR TO 
LAST FEW RUNS OF UKMET WITH SYSTEM DROPPING SOUTH THROUGH PLAINS AND THEN
SHEARING E/SE IN CONFLUENT FLOW INTO MID MISSISSIPPI VALLEY ON TUE... 
WHICH MAKES SENSE CONCEPTUALLY AND AGREES WITH PAST ENSEMBLE MEMBERS. 
AVN/GFS OUTLIER AND RETROGRADES SYSTEM THROUGH THE GREAT BASIN FORMING VIGOROUS
CLOSED SYSTEM OVER CALIFORNIA WED. 

EXTENDED (WED-SAT)
QUICK MOVING SYSTEM SLATED FOR THANKSGIVING. LOOKS LIKE BULK OF FORCING NORTH
BUT THAT FAR OUT WILL MAINTAIN CHC PCPN. MODELS THEN OVERALL SUGGEST
UPPER RIDGE TO BUILD FROM WESTERN STATES INTO CENTRAL U.S. END OF WEEK INTO
WEEKEND RESULTING IN MODERATING TEMPS AND TRANQUIL WX.

COORD WITH ILX...LOT...LSX...THANX!  DMX...EAX...THANX FOR THE CHAT!

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

05