FXUS63 KLSX 022358
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
558 PM CST WED DEC 2 2009

.DISCUSSION...
/312 PM CST WED DEC 2 2009/

SURFACE LOW CENTERED OVER WESTERN TN WILL CONTINUE TO LIFT TO THE 
NORTHEAST TONIGHT AND WILL BE OVER WESTERN NY BY THURSDAY MORNING. 
IN THE MEANTIME...MAIN FORECAST ISSUE IN THE SHORT TERM IS PCPN THAT 
WILL BE COMING TO AN END TONIGHT AND TEMPERATURES OVER THE NEXT 
SEVERAL DAYS AS RIDGE OF HIGH PRESSURE BUILDS IN.

SO FAR THIS AFTERNOON...SLOWER ONSET OF PRECIP AND SLOWER PUSH OF 
COLD AIR INTO BACK SIDE OF STORM SYSTEM HAS KEPT SNOWFALL AT BAY.  
WE DID GET A REPORT OF SNOW MIXING IN WITH THE RAIN OVER MONTGOMERY 
COUNTY IL DURING THE LAST HOUR AND STILL THINK THAT STRONG UVV WITH 
FRONTAL SCALE FORCING...AND PERHAPS JUST A BIT OF COOLING THAT WILL 
OCCUR WITH SUNSET...MAY COOL THE COLUMN JUST ENOUGH THAT WE COULD 
GET A VERY MINOR ACCUMULATION BEFORE THE PRECIP TOTALLY SHUTS DOWN 
LATER THIS EVENING.  HAVE TRIED TO FOCUS THIS ACCUMULATION...UNDER 
ONE-HALF INCH....ON THE BRIGHT BAND NOW SHOWING UP ON LSX 88D... 
ROUGHLY FROM JUST E OF DOWNTOWN TO NEAR TAYLORVILLE IL.  OTHERWISE 
...IT CERTAINLY APPEARS THAT THE BULK OF THE MEASURABLE PRECIP FOR 
TONIGHT WILL OCCUR ALONG AND EAST OF A UNO-STL-SPI LINE...AND 
PRIMARILY IN THE 00Z-03Z TIME FRAME.

BEYOND THAT VERY COLD TEMPERATURES ARE EXPECTED THURSDAY THROUGH 
FRIDAY DUE TO A PROLONGED PERIOD OF LOW LEVEL CAA WITH 850 MB 
TEMPERATURES CONTINUING TO FALL...EVENTUALLY DROPPING TO -12 TO -13 
ACROSS MOST OF THE AREA BY 12Z FRI.  AS FOR ANY PCPN CHANCES...WITH 
CLOUDS LINGERING...ESPECIALLY OVER NORTHEAST MO AND WEST CENTRAL 
IL...CAN EXPECT SOME FLURRIES THURSDAY AS ANOTHER SHORTWAVE ROTATES 
AROUND UPPER LOW OVER THE GREAT LAKES. DO NOT EXPECT ANY 
ACCUMULATIONS WITH THIS SHORTWAVE.

FRIDAY NIGHT...RIDGE OF HIGH PRESSURE TO BEGIN MOVING OFF TO OUR 
EAST...ALLOWING SOUTHERLY WINDS TO RETURN ONCE AGAIN. SO WILL SEE 
TEMPERATURES MODERATE OVER THE WEEKEND WITH HIGHS IN THE UPPER 30S 
TO LOWER 40S SATURDAY AND SUNDAY.

BEYOND THAT...MODELS INDICATING ANOTHER DEVELOPING WEATHER SYSTEM 
APPROACHING THE REGION FROM THE SOUTHWESTERN U.S. ON MONDAY...WITH 
BEST CHANCES OF PRECIPITATION TUESDAY THROUGH WEDNESDAY. THE 
PRECIPITATION WILL BE A MIXTURE OF LIGHT RAIN AND SNOW AT TIMES...AS 
DAYTIME TEMPS WILL BE IN THE MID 30S TO LOWER 40S AND LOWS IN THE 
MID TO UPPER 20S. STILL NOT CONFIDENT ON EXACT TIMING AND LOCATION 
OF SYSTEM...SO KEPT POPS IN THE LOW CHANCE/SLIGHT CHANCE CATEGORY 
FOR NOW.

BYRD

&&

.AVIATION...
/547 PM CST WED DEC 2 2009/

FOR THE 00Z TAFS...
MARGINAL CIGS AND VSBYS WILL PREVAIL THIS EVENING IN LIGHT RAIN
AS THE STORM SYSTEM AFFECTING THE REGION CONTINUES MOVING EAST.
FLIGHT CONDITIONS WILL OCCASIONALLY DROP TO HIGH END IFR AS RAIN
MIXES WITH OR CHANGES TO LIGHT SNOW. OTHER THAN THE INTERMITTENT
IFR...I DON'T EXPECT ANY IMPACTS FROM THE SNOW OTHER THAN WET
RUNWAY/RAMP CONDITIONS. ALL PRECIP SHOULD CLEAR THE AREA BY 06Z.
WITH FLIGHT CONDITIONS IMPROVING TO VFR ON THE BACK SIDE OF THE
STORM. NORTHWEST WINDS OF 12-15KTS WILL PREVAIL...OCCASIONALLY
GUSTING TO 25-30KTS. SHOULD SEE THE GUSTS DIE DOWN LATER
TONIGHT...BUT PICK BACK UP THURSDAY MORNING A FEW HOURS AFTER
SUNRISE WHEN WE GET SOME MIXING IN THE LOW LEVELS.

CARNEY

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

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