FXUS62 KCAE 240852
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
352 AM EST THU DEC 24 2009

.SYNOPSIS...
A STORM SYSTEM WILL APPROACH FROM THE SOUTHWEST LATER TONIGHT
THROUGH CHRISTMAS DAY. DRY HIGH PRESSURE WILL THEN RETURN OVER THE
WEEKEND AND INTO NEXT WEEK.

&&

.NEAR TERM /TODAY/...
SATELLITE IMAGES THIS MORNING SHOWING STRONG UPPER LEVEL LOW IS
MOVING INTO WESTERN TEXAS...WITH ANOTHER LOW MOVING THROUGH THE
UPPER MIDWEST. THESE TWO UPPER LEVEL LOWS ARE FORECAST TO BEGIN
PHASING TOGETHER OVER THE CENTRAL PLAINS LATER TODAY. MAIN SURFACE
LOW WILL TRACK NORTHWARD OUT OF EASTERN TEXAS...WITH SURFACE COLD
FRONT MOVING EAST THIS AFTERNOON.

OVER OUR REGION...HIGH PRESSURE WILL BEGIN TO WEAKEN AND MOVE
NORTHWARD DURING THE AFTERNOON. ISENTROPIC LIFT FROM SOUTHWESTERLY
WINDS RIDING OVER RETREATING COOL AIRMASS WILL ALLOW RAIN TO
BEGIN TO DEVELOP ACROSS PORTIONS OF GA THIS AFTERNOON. CLOUD COVER
AND RAIN CHANCES WILL GRADUALLY INCREASE ACROSS THE CSRA LATER
THIS AFTERNOON. AFTERNOON HIGHS WILL RANGE FROM THE LOWER 50S
NORTH TO THE UPPER 50S SOUTH.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... 
MAIN UPPER LEVEL SHORTWAVE TROUGHS OVER THE MIDWEST MERGE TOGETHER
OVERNIGHT TONIGHT. THIS MAIN UPPER TROUGH WILL THEN BEGIN MOVING
EAST...BREAKING DOWN THE UPPER RIDGE CURRENTLY OVER THE SE US...INTO
FRIDAY NIGHT. DEEPENING SURFACE LOW WILL MOVE NORTHWARD THROUGH
THE MID MISSISSIPPI RIVER REGION. SURFACE COLD FRONT WILL BE
MOVING THROUGH THE GULF COAST STATES AND THE SOUTHEAST FRIDAY AFTERNOON
INTO FRIDAY NIGHT. RETREATING SURFACE WEDGE AIR OVER THE SE US
WILL ALLOW FOR A WARM FRONT TO DEVELOP LATE TONIGHT OVER SOUTHERN
GA...AND MOVE NORTHWARD THROUGH OUR REGION FRIDAY. GOOD
INSENTROPIC LIFT WILL CONTINUE LATE TONIGHT INTO FRIDAY IN ADVANCE
OF THE WARM FRONT. HAVE GONE CATEGORICAL POPS OVERNIGHT AND INTO
FRIDAY OVER THE ENTIRE CWA. COULD SEE SOME ELEVATED INSTABILITY
LATE TONIGHT INTO FRIDAY....WITH AN ISOLATED THUNDERSTORM BEING
POSSIBLE. CONFIDENCE LOW RIGHT NOW...THUS HAVE LEFT OUT OF GRIDS
FOR NOW. RAIN MOVES EAST OF THE REGION FRIDAY NIGHT. SURFACE WINDS
OVERNIGHT INTO FRIDAY WILL BE ON THE INCREASE AND COULD GE A
LITTLE GUSTY ON AREA LAKES LATE TONIGHT AND FRIDAY.

LOWS TONIGHT IN THE 40S. EXPECTED SURGE OF WARM AIR FRIDAY WILL
ALLOW TEMPS TO WARM INTO THE MID 50S TO LOWER 60S IN SPITE OF
CLOUDS AND RAIN.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
FEW CHANGES MADE IN THE EXTENDED.  LARGE POLAR VORTEX OVER THE MID
MS RIVER VALLEY TO SLOWLY MOVE NORTHEAST ACROSS THE GREAT LAKE
REGION INTO NEW ENGLAND THROUGH TUESDAY.  MEDIUM RANGE MODELS
SHOWING SLIGHT FLATTENING OF THE UPPER PATTERN THE SOUTHEAST
TUESDAY AND WEDNESDAY.  HIGH PRESSURE BUILDING IN FROM THE WEST
SATURDAY THROUGH TUESDAY. WEST/NORTHWEST FLOW AT H850 WILL KEEP
THE GULF CLOSED. DRY AND COOL PERIOD EXPECTED. BY WEDNESDAY,
SURFACE RIDGE MOVING OFF THE EAST COAST AND ANOTHER LOW PRESSURE
SYSTEM WILL BE CROSSING THE GULF BY THURSDAY. 

SO...A RAIN-FREE AND RELATIVELY TRANQUIL PERIOD IS EXPECTED THIS 
WEEKEND THROUGH MIDWEEK. HIGH TEMPERATURES WILL BE AROUND NORMAL 
SATURDAY...THEN BELOW NORMAL TEMPERATURES SUNDAY THROUGH MIDWEEK.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
HIGH PRESSURE WILL CONTINUE TO WEDGE DOWN INTO THE REGION THROUGH 
THE TAF PERIOD. SATELLITE LOOP SHOWS PLENTY OF MID/HIGH CLOUDS 
MOVING ACROSS THE REGION TONIGHT. LOOKS LIKE THERE MAY BE A BIT OF A 
BREAK FROM THE HIGH CLOUDS FOR A FEW HOURS...BEFORE MORE CLOUDINESS 
BEGINS TO SPREAD INTO THE REGION. TIME SECTIONS SHOW LOW LEVEL 
MOISTURE TO BEGIN INCREASING ACROSS THE AREA THURSDAY MORNING. BOTH 
NAM/GFS SHOW ISENTROPIC LIFT INCREASING THROUGH THE DAY ON 
TUE...ESPECIALLY BY THE AFTERNOON/EVENING PERIOD. LLJ WILL INCREASE 
A LITTLE OVERNIGHT AND EXPECT WINDS TO REMAIN FROM THE NE AT 4 TO 5 
KNOTS. CONDITIONS WILL REMAIN VFR TONIGHT AND INTO THURSDAY...BUT AS 
ISENTROPIC LIFT INCREASES THROUGH THE DAY EXPECT MVFR 
CONDITIONS...DUE TO CLOUDS...TO DEVELOP BETWEEN 22-23Z. PCPN LOOKS 
TO ARRIVE CLOSE TO 06Z AND FOR NOW WILL NOT MENTION ANY PCPN IN THE 
TAFS.  
 
EXTENDED AVIATION OUTLOOK...MVFR CONDITIONS POSSIBLE THURSDAY NIGHT 
INTO FRIDAY AS A STORM SYSTEM MOVES THROUGH THE REGION. HIGH 
PRESSURE WILL BUILD INTO THE REGION FOR FRIDAY NIGHT THROUGH MONDAY.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.

&&

$$