[LeArc] Forecast Discussion : MLI@ 10/23/02 3:17:51 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 232026
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
326 PM CDT WED OCT 23 2002

1039 HIGH WAS CENTERED OVER SOUTHEAST ND AT 18Z WITH RIDGE EXTENDING 
SOUTH INTO TX PANHANDLE. WIDESPREAD SNOW CONTINUES IN UPSLOPE AREA 
AND WESTERN EDGE OF BAROCLINIC ZONE FROM SD INTO KS. AT H5 ZONAL TO 
SW FLOW WITH MAIN TROUGH FROM CENTRAL CANADA TO ID AT 12Z. SEVERAL 
EMBEDDED SHORTWAVES IN W-SW FLOW ENHANCING CURRENT UPSTREAM 
PRECIPITATION TAKING AIM AT FORECAST AREA TONIGHT. FORECAST 
CHALLENGE IS PRECIPITATION CHANCES TONIGHT THROUGH FRIDAY AS 
BAROCLINIC BOUNDARY LINGERS.

AVN SURFACE FEATURES...QPF...AND LOCATION OF H5 VORT MAXES MATCHED 
BEST WITH REALITY AT 18Z AND THUS MAINLY FOLLOWED. WATER VAPOR 
IMAGERY SHOWED MOST SIGNIFICANT WAVE MOVING INTO SE KS WITH WEAKER 
FEATURES TO IMPACT FORECAST MOVING INTO SW NEB AND WESTERN SD. 
DYNAMIC FORCING FROM KS WAVE WILL IMPACT SW ZONES BY EARLY 
EVENING...THEN LIFT MAXES OUT ABOUT 06Z OVER ENTIRE AREA. AT SAME 
TIME...WEAK EASTERLY FLOW AT H85 VEERS TO SOUTH AS WEAK LOW OVER 
WEST TX MOVES EAST. THIS RESULTS IN H85 WARM AIR ADVECTION OVERNIGHT 
ALONG WITH A PERIOD OF ISENTROPIC UPGLIDE. RESULTING PRECIPITATION 
WILL BE IN THE FORM OF SNOW ACROSS HIGHWAY 20 CORRIDOR BASED ON 
CRITICAL THICKNESS VALUES AND FORECAST SOUNDINGS. WITH ABOUT AN 8 
HOUR PERIOD OF LIGHT SNOW...SNOW SHOULD BE EVENTUALLY BE ABLE TO 
OVERCOME WARM GROUND AND PER COORDINATION WITH ARX AND DMX WILL 
LEAVE IN MENTION OF UP TO ONE INCH ACCUMULATIONS ON GRASSY AREAS. 
FURTHER SOUTH...EXPECT SNOW MIXED WITH SOME RAIN AT TIMES IN MIDDLE 
SET OF ZONES...AND ALL RAIN SOUTH OF HIGHWAY 34. HAVE RAISED POPS TO 
CATEGORICAL AS AREA 88DS SHOW PRECIP ON THE WAY.

MAIN LIFT EXITS TO THE EAST LATE THURSDAY MORNING...BUT WARM AIR 
ADVECTION CONTINUES ACROSS MAINLY NORTHERN ZONES TO KEEP LOW POPS
GOING THERE THROUGH EARLY AFTERNOON. EAST WINDS AND CLOUD COVER WILL
PREVENT TEMPERATURES FROM RISING MUCH AND STAYED ON THE COOL SIDE OF 
GUIDANCE CLOSEST TO MAV. ANOTHER SIGNIFICANT WAVE IN SW FLOW WILL 
BRING PRECIP CHANCES AGAIN THURSDAY NIGHT WITH BEST LIFT ACROSS 
SOUTH. AS H85 LEE TROUGH DEVELOPS...RESULTING STRENGTHENING LOW 
LEVEL WARM AIR ADVECTION WILL PREVENT MUCH TEMPERATURE DROP OFF AND 
LIMIT SNOW THREAT TO FAR NORTHERN ZONES WITH RAIN MENTIONED 
ELSEWHERE. LINGERING MOISTURE WILL KEEP SKIES MOSTLY CLOUDY FRIDAY 
AND LIMIT HIGHS IN 40S. 

IN EXTENDED...MEDIUM RANGE MODELS SHOW NEXT SIGNIFICANT SHORTWAVE 
MOVING OUT TO BRING NEXT PRECIP CHANCES SUNDAY NIGHT AND MONDAY.
THEN LONG TROUGH AROUND CENTRAL CAN LOW TO KEEP COOL AND UNSETTLED
CONDITIONS THROUGH MIDWEEK. FOLLOWING MRF AND UK...LOOKS LIKE 
TUESDAY SHOULD BE DRY AND ALSO INTRODUCED WED AS DRY FOR NOW. 
CONTINUED MUCH BELOW NORMAL TEMPERATURES. 

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

DLS