FXUS62 KGSP 160550
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1250 AM EST WED DEC 16 2009

.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD IN FROM THE WEST TODAY...THEN 
GRADUALLY WEAKEN AND MOVE EAST OF THE AREA BY FRIDAY.  LOW PRESSURE 
WILL DEVELOP ACROSS THE GULF OF MEXICO LATE IN THE WEEK AND MOVE UP 
THE ATLANTIC COASTLINE OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
EXPANSIVE SHIELD OF HIGH CLOUDS SHOULD CONT TO STREAM OVER REGION 
WAVE DEVELOPS OVER NW GULF AND SLOWLY TRACKS E. CAA WILL HELP KEEP 
WINDS GUSTY MTNS WITH GAP WINDS INTO GSP AREA. WILL KEEP LAKE WIND 
FOR CURRENT AREA THRU 11Z. SFC HIGH PRESSURE WILL CONTINUE TO BUILD 
INTO THE REGION FROM THE N THRU TONIGHT. EVEN WITH HIGH CLOUDS 
TODAY...DOWNSLOPE WINDS WILL HELP HI TEMPS ACROSS THE PIEDMONT REACH 
NEAR AVG. HIGHS IN THE MTNS WILL BE A FEW DEG BELOW AVG. LOWS 
TONIGHT WILL COOL INTO THE M20S TO AROUND 30 IN THE PIEDMONT WITH 
L-M20S MTNS.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 235 PM TUESDAY...BEGINNING OF SHORT TERM WEATHER EXPECTED TO 
BE RATHER TRANQUIL AS A SPRAWLING AREA OF HIGH PRESSURE FROM THE 
GREAT LAKES INTO THE TN VALLEY MAINTAINS CONTROL OF THE WEATHER WED 
NIGHT THROUGH PROBABLY THU NIGHT. CONDITIONS WILL BE GENERALLY CLEAR 
WITH SEASONAL TEMPS DURING THAT TIME PERIOD...WITH INCREASING 
CLOUDINSS LATE THU NIGHT. THINGS QUICKLY BECOME MORE INTERESTING AND 
COMPLICATED LATE IN THE WEEK AS CYCLOGENESIS COMMENCES IN THE 
WESTERN GOM ON THU IN RESPONSE TO DIGGING UPPER TROUGH OVER THE 
MIDSECTION OF THE COUNTRY. THIS LOW TRACKS EASTWARD AND WILL 
PROBABLY MOVE ACROSS NORTHERN FLORIDA ON FRI AND THEN TO SOMEWHERE 
OFF THE SC COAST BY 12Z SAT. ALL MODELS AGREE ON THE CYCLOGENESIS IN 
THE GULF AND THE EASTWARD MOVEMENT OF THE LOW...BUT FOR OUR AREA THE 
DETAILS ON HOW THE LOW WILL ULTIMATELY INPACT THE WESTERN CAROLINAS 
AND NE GA IS STILL RATHER HAZY. THE 12Z GFS SOLUTION IS QUITE 
BULLISH ON QPF AND COLD ENOUGH FOR FROZEN PRECIP ACROSS MOST THE 
AREA. HOWEVER...THIS SOLUTION IS IN DOUBT AS UPPER TROUGH NEVER 
REALLY TAKES ON A NEG TILT AND OTHER MODEL SOLUTIONS FOR THE AREA 
NOT AS COLD. THE 12Z ECM HAS THE HEAVIEST PRECIP GENERALLY S OF I-85 
AND 12Z GEM EVEN FARTHER S. SO TAKING A MODEL BLEND WOULD FAVOR 
HIGHEST POPS/QPF ACROSS NE GA/THE PIEDMONT OF SC WITH LIGHTER QPF 
EXTENDING NORTH INTO WESTERN NC. IN REGARD TO WEATHER TYPE...A BLEND 
OF GFS/ECM THICKNESS FIELDS AND UTILIZING THE TOP DOWN METHOD WOULD 
FAVOR A WINTERY MIX EARLY ON FRI OVER NE GA...SOUTHERN UPSTATE...BUT 
ALL RAIN ACROSS THE UPSTATE IN THE AFTERNOON. A WINTERY MIX THEN 
RETURNS FRI NIGHT INTO SAT. AT THIS POINT...CAN'T RULE OUT SOME 
ACCUMULATING SNOW...BUT RIGHT NOW IT LOOKS TOO PROBLEMATIC TO BE 
DEFINITIVE IN ANY WAY. HAVE COOLED MAX TEMPS CONSIDERABLY BELOW GUID 
ON FRI/SAT IN DEFERENCE OT CLOUDS AND PRECIP.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 200 PM TUESDAY...THE EXT RANGE BEGINS WITH THE INTRODUCTION OF 
MORE MODEL SPREAD AND UNCERTAINTY. THE 12Z GFS AND 12Z GEM BECOME 
MORE AGREEABLE WITH THE UPPER PATTERN...WHILE THE 00Z ECMWF LOOKS 
MORE AND MORE LIKE THE OUTLIER. WRAP AROUND MOISTURE STILL LOOKS 
GOOD...BUT NOT AS PROLONGED AS THE ECMWF TAKES IT WITH ITS STRONG 
POLAR VORTEX CROSSING OVER THE MIDWEST AND OH VALLEYS LATE SUN 
THROUGH WED. THE EASTWARD SHIFTING UVLV RIDGE DEPICTED BY THE GEM 
AND THE GFS IS GOING TO BE GIVEN MORE CREDENCE IN THIS FCST 
PACKAGE...WHICH THEREFORE ACCOUNTS FOR A LOW END WRAP AROUND 
EVENT...FOLLOWED BY ANOTHER BROAD ARCTIC HIGH DEVELOPING ACROSS THE 
MID/ATL AND SE REGION BEGINNING SUN AFTERNOON. 

SO...POPS WILL BE ADJUSTED UP TO LOW END CHANCE ACROSS THE NC MTNS 
SAT NIGHT...LOWERING TO SLIGHT CHANCE AFTER 12Z AS LLVL MOISTURE IS 
QUICK TO DIMINISH. THE EXPECTED P/TYPE WILL BE ALL -SNSH...EXCEPT 
FOR -SHRA ACROSS THE DOWNSLOPING AREAS EAST OF THE NRN FOOTHILLS. 
QPF IS STILL NOT CERTAIN...BUT THE OVERALL PROGRESSIVE PATTEN MAKES 
THE CASE FOR ADDITIONAL SN ACCUM ON THE LOW END ...MOST LIKELY 
AROUND AN INCH OR LESS ACROSS THE HIGHER ELEVATIONS. 

THE OP MODELS DO AGREE ON A SIGNIFICANT LOWERING AND MAINTENENCE OF 
THE LLVL THICKNESSES REGARDLESS OF THE ARCTIC HIGH PLACEMENT THROUGH 
THE EXT. THIS GIVES DECENT CONFIDENCE IN ADVERTISING MAX TEMPS 
SUN/MON ABOUT 10 DEGREES BELOW CLIMO EVEN WITH THE INCREASED 
INSOLATION ANTICIPATED. RETURN SSW/LY FLOW IS MOST LIKELY TO DEVELOP 
BY NEW DAY 7...WHICH SHOULD ALLOW MAX TEMPS TO REACH A COUPLE 
DEGREES BELOW NORMAL.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
KCLT AND ELSEWHERE...BKN-OVC CIRRUS WITH N-NE WINDS GENERALLY LESS 
THAN 10 KTS...EXCEPT GUSTS OVER 20KT KAVL...KGSP AND KGMU WHICH WILL 
SLOWLY DECREASE OVERNIGHT...REMAINING GUSTY AROUND 20KT AT KAVL THRU 
THE DAY.

OUTLOOK...UNRESTRICTED CIG/VSBY WED NIGHT-THU IN DRIER AIRMASS. A STORM
SYSTEM APPROACHES FROM THE SW FRI...POSSIBLY BRINGING LOWER CIG/VSBY 
WITH RAIN AND/OR SNOW SHOWERS FRI-SAT. THEN NW FLOW SNOW OVER MTNS 
SUN-MON.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...LAKE WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR 
     NCZ033-048>050-053-064-065-501-503-505-507-509.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...RB
SHORT TERM...LG
LONG TERM...SBK
AVIATION...RB