FXUS62 KGSP 101749
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1249 PM EST THU DEC 10 2009

.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD ACROSS THE FORECAST AREA TODAY WHILE 
A COLD FRONT CONTINUES TO WEAKEN OFF THE EAST COAST. MOISTURE WILL 
INCREASE FROM THE SOUTH THROUGH SATURDAY AS AN AREA OF LOW PRESSURE 
MOVES EAST ALONG THE NORTHERN GULF COAST. THIS LOW WILL MOVE UP THE 
CAROLINA COASTLINE THROUGH SUNDAY...BEFORE A WEAK AREA OF HIGH 
PRESSURE BUILDS OVER THE AREA MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
THE UPPER TROUGH OVER THE CONTINENTAL US WILL PROGRESS AND DEAPMLIFY 
TONIGHT AND FRIDAY...WITH ZONAL FLOW OVER THE SOUTHEAST. A SURFACE 
HIGH WILL MOVE FROM THE MID MS RIVER VALLEY TO THE CENTRAL 
APPALACHIANS. THE PRESSURE GRADIENT ON THE EAST SIDE OF THIS HIGH 
WILL RELAX OVER THE SOUTHERN APPALACHIANS TONIGHT...WITH GUSTY WINDS 
REMAINING ONLY IN THE MOUNTAINS. THE WIND ADVISORY FOR THE NORTHERN 
NC MOUNTAINS WILL BE EXTENDED TIL MIDNIGHT...AS WILL THE LAKE WIND 
ADVISORY FOR THE CENTRAL NC MOUNTAINS. WITH LIGHT WINDS TONIGHT EAST 
OF THE MOUNTAINS AND ONLY SCATTERED CIRRUS...RADIATIONAL COOLING 
WILL TAKE MINIMUM TEMPERATURES SEVERAL CATEGORIES BELOW NORMAL AS 
THE COLD AIR MASS CROSSES THE MOUNTAINS. THE MOUNTAINS WILL ONLY BE 
A FEW DEGREES COOLER AS WINDS KEEP THE BOUNDARY LAYER MIXED.

CIRRUS INCREASES ON FRIDAY OVER THE SOUTHERN PERIPHERY OF THE 
SURFACE RIDGE...WELL NORTH OF A SURFACE FRONT IN THE GULF OF MEXICO. 
WINDS WILL BE LIGHT FROM THE NORTHWEST. MAXIMUMS TEMPERATURES WILL 
WARM TO NEAR NORMAL ALONG AND SOUTH OF INTERSTATE 85...BUT WILL BE 
SEVERAL CATEGORIES BELOW NORMAL ALONG INTERSTATE 40.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 215 AM THURSDAY...HIGH PRESSURE WILL REMAIN OVER THE REGION ON 
FRIDAY. CONFLUENT UPPER TROPOSPHERIC FLOW AND A 180+ KT JET WILL 
PROVIDE PLENTY OF SUPPORT FOR THE RIDGE. THICKNESSES WILL BE QUITE 
LOW...AND MAX TEMPS WON/T CLIMB OUT OF THE L-M40S OVER THE FOOTHILLS 
AND PIEDMONT AND THE 30S IN THE MTNS. HIGH CLOUDS WILL BE ON THE 
INCREASE...WHICH COULD KEEP MAXES EVEN A HAIR COOLER.

AS THE PREVIOUS SHIFT NOTED...WE ARE DEALING WITH LOW AMPLITUDE SRN 
STREAM SHORT WAVES WITH THIS NEXT PCPN EVENT...A TYPICAL BANE OF AN 
EL NINO WINTER. WHEN THE FORCING IS THIS WEAK...IT/S HARD TO KNOW 
JUST WHEN THE LLVL WARM ADVECTION WILL BECOME STRONG ENOUGH TO 
SUPPORT PCPN. ALSO...WITH SUCH A DRY RIDGE OF ARCTIC ORIGINS OVER 
THE REGION...THE WESTERN CAROLINAS WILL BE ONE OF THE LAST PLACES TO 
SEE PCPN OWING TO THE DEEP MASS OF COOL...DRY AIR. I/VE PUSHED 
TIMING BACK AGAIN...AND NOW DON/T HAVE PCPN STARTING OVER THE REGION 
UNTIL SAT AFTN. EVEN THIS COULD BE OVERDONE AS THE STRONGEST FORCING 
ON THE LATEST MODEL RUNS LOOKS TO REMAIN OVER THE MIDLANDS AND LOW 
COUNTRY.

THERE WILL BE ENOUGH OF A WARM NOSE...THAT ONLY A BRIEF PERIOD OF 
SNOW IS POSSIBLE ON SAT...MAINLY OVER THE MTNS. SOME SLEET IS 
PROBABLE OVER WRN NC SAT AFTN AND EVENING...AND MAYBE A LITTLE 
FREEZING RAIN OVER THE MTNS SAT NIGHT AND SUNDAY MORNING AS THE CAD 
REGION MOISTENS. I/VE CUT WAY BACK ON QPF...AND UNLESS THE MODELS 
SHIFT THE PCPN CONSIDERABLY FARTHER NORTH...WE ARE NOT LOOKING AT 
MUCH OF A WINTER PCPN EVENT OVER THE NC FOOTHILLS AND PIEDMONT. 
PERHAPS THERE WILL BE ENOUGH PCPN FOR A WINTER WEATHER 
ADVISORY...BUT THAT/S NOT LOOKING VERY LIKELY.

TEMPS WILL WARM ENOUGH ON SUNDAY FOR ANY FZRA OR SLEET OVER THE NC 
ZONES TO CHANGE TO RAIN. THE MODELS PUSH A WEAK LOW UP THE COAST 
DURING THE DAY AS THE LAST IN A SERIES OF ILL-DEFINED SRN STREAM 
SHORT WAVES MOVES EAST OF THE REGION...FOLLOWED BY A BRIEF PERIOD OF 
SHORT WAVE RIDGING.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 AM THURSDAY...THERE IS LITTLE NEED TO ADJUST THE GOING 
FORECAST BASED OF THE LATEST OBJECTIVE GUIDANCE. THE OP MODELS 
AGREE PRETTY WELL WITH DEVELOPING A DEEP E COAST TROF BY MID NEXT 
WEEK...WITH VARYING DIFFERENCES AS HOW MUCH SPLIT FLOW WILL 
DEVELOPED. THE ECMWF IS MORE SPLIT WITH THE UPPER JET PATTERN AND 
THEREFORE MORE ZONAL AND WARMER THAN THE GFS. THUS...THE ECMWF LOOKS 
SLOW IN BRINGING THE ARCTIC AIRMASS INTO THE UPPER MIDWEST...WHEN 
COMPARED TO THE MORE PROGRESSIVE GFS. 

IN ANY REGARD...THE LLVL SYNOPTIC PATTERN IS RELATIVELY CLOSE WRT 
THE FAST MOVING CLIPPER CROSSING THE OH VALLEY AND INTO S QUEBEC BY 
MON NIGHT. THE MAIN ACTION FOR THE CWFA WILL BE THE AMOUNT GOM 
MOISTURE FLUX REACHING THE AREA BEFORE A RATHER STRONG ARCTIC HIGH 
BUILDS IN FROM THE NW. STILL EXPECT A S/W RIDGE TO CROSS THE REGION 
MON KEEPING THINGS DRY...AND WITH DECENT S/LY FLOW THROUGHOUT THE 
DAY MAX TEMPS SHOULD HAVE NO PROBLEM MODIFYING ABOUT 10 DEGREES 
WARMER THAN SUN. 

ITS INTERESTING THAT BOTH MODELS SHOW COMPARABLE PLACEMENT AND 
STRENGTH OF THE SOUTHERN STREAM CONVECTION...EVEN THO THE ULVL 
PATTERNS ARE SO DIFFERENT BETWEEN THEM. WITH THE GEFS ENS MEMBERS 
HAVING MUCH LESS SPREAD IN THE SOUTHERN STREAM COMPONENT THAN THE 
NORTHERN S/W TROF...THERE IS REASONABLE CONFIDENCE THAT THE ECMWF/S 
SPLIT FLOW SOLN IS PROBABLY SUPPORTED BY THE GFS MORESO THAN THE OP 
MODELS MAY INDICATE....ESP GIVEN THE RECENT DEC PATTERN.
 
SO...SUFFICE TO SAY THE TIMING OF GOM MOISTURE WILL BE WEIGHTED 
MORESO WITH THE MOISTURE FLUX OF THE ECMWF. THIS AGREES WELL WITH 
CONTINUING THE HIGH CHANCE POPS FOR TUE AND HPC 18Z GUIDE. THE LLVL 
THERMAL FIELDS ARE ON TRACK WITH THE PREVIOUS FORECAST AS WELL...SO 
ISOL WRAP AROUND NC MTN SN SHOWERS STILL LOOK GOOD TUE NIGHT WITH 
LLVL MOISTURE WANING QUICKLY BY 12Z WED.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...GUSTY WNW WINDS WILL CONTINUE THIS AFTERNOON...THEN 
FUSTINESS WILL DIMINISH THIS EVENING. BY LATE TONIGHT LIGHT 
NORTHWEST WINDS WILL PREVAIL...WHICH WILL CONTINUE THROUGH FRIDAY 
MORNING. FEW TO SCATTERED CIRRUS WILL ARRIVE TONIGHT.

AT KAVL AND KHKY...A GRADUAL DECREASE IN GUSTY NW WINDS WILL OCCUR 
AT KAVL TONIGHT AND FRIDAY MORNING...WHILE KHKY LOSES ITS WIND 
GUSTS THIS EVENING. A FEW TO SCATTERED CIRRUS WILL INVADE FORM THE 
SOUTHWEST.

FOR UPSTATE SC SITES...WINDS SHOULD REMAIN STEADY AND FROM THE W 
BECOMING MORE NW THIS EVENING AND EVENTUALLY MORE NORTHERLY EARLY 
TOMORROW WHILE DECREASING TO WITHIN THE 5 KT RANGE. MOSTLY CLEAR 
SKIES WILL GIVE WAY TO SCATTERED HIGH CLOUDS THIS EVENING. 

OUTLOOK...VFR EXPECTED LATE FRIDAY. A GULF COAST STORM SYSTEM COULD 
SPREAD LIGHT MIXED PRECIP INTO THE REGION SATURDAY AFTERNOON INTO 
THE NIGHT. FLIGHT RESTRICTIONS COULD LINGER INTO SUNDAY. VFR MONDAY.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ033-049-050-
     501-503-505.
     LAKE WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ048-052-
     053-064-065-507-509.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...JAT
SHORT TERM...MCAVOY
LONG TERM...SBK
AVIATION...JAT/JPT