FXUS62 KGSP 081756
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1256 PM EST TUE DEC 8 2009

.SYNOPSIS...
DEEP MOISTURE WILL SPREAD ACROSS THE FORECAST AREA FROM THE WEST 
TODAY AS A STRONG LOW PRESSURE SYSTEM ORGANIZES OVER THE PLAINS. 
THIS LOW WILL MOVE NORTHEASTWARD TOWARD THE GREAT LAKES TONIGHT... 
PUSHING A COLD FRONT ACROSS THE SOUTHERN APPALACHIANS ON WEDNESDAY. 
A LARGE AREA OF HIGH PRESSURE WILL BUILD IN FROM THE WEST ON 
THURSDAY AND REMAIN OVER THE MID ATLANTIC INTO THE WEEKEND AS A 
WEAKER LOW PASSES JUST SOUTH OF OUR AREA.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOW PRESSURE WILL SLIDE ACROSS THE CENTRAL PLAINS AS WEAK HIGH 
PRESSURE REMAINS RIDGED ALONG THE EAST FACING SLOPES OF THE 
APPALACHIANS TODAY. FLOW AROUND THE LOW WILL STEADILY STRENGTHEN 
OVER THE REGION THROUGH THE AFTERNOON. DEEP ISENTROPIC LIFT IS 
FORECAST TO DEVELOP ACROSS THE CWA THIS AFTERNOON. AT 16Z...THE 
REGION OF ISENTROPIC LIFT WAS LOCATED ACROSS CENTRAL AND NE GA AND 
CORRESPONDED WITH A REGION OF WIDESPREAD STRATIFORM RA. I WILL KEEP 
CATE POPS ACROSS THE CWA BY LATE THIS AFTERNOON. TEMPERATURES WILL 
REMAIN STEADY OR SLOWLY FALLING THROUGH THE REST OF TODAY. THE 
COOLEST TEMPERATURES SHOULD REMAIN ALONG THE EASTERN UPSLOPE AREAS 
OF THE NRN MTNS...FAVORING VALUES IN THE 33-35 DEGREE RANGE. TEMPS 
MAY START TO RISE OVERNIGHT AS RETURN FLOW STRENGTHENS AHEAD OF A 
COLD FRONT. I WILL INCLUDE NON DIURNAL TEMPS WITH THIS UPDATE.

AFOREMENTIONED 60+ KT LLVL JET WILL TRANSLATE ENE ACRS THE CWFA 
TONIGHT. Q-VECTOR ANALYSIS INDICATES THE STRONGEST DEEP FORCING WILL 
BYPASS THE CWFA TO OUR NW...BUT COINCIDENT WITH THE LIFT RESULTING
FROM THE STOUT LLVL WAA FLOW...PERIODS OF HEAVY RAIN ARE EXPECTED TO 
DEVELOP. MODEL CONSENSUS QPF...A BROAD MAXIMA ALONG AND EAST/SOUTH
OF THE BLUE RIDGE INDICATES THAT THE CHANCES FOR EXCESSIVE RAIN WILL 
BE LIMITED. THE POTENTIAL FOR HIGHER ELEVATION 60 KT WIND GUSTS
IS INCREASING...BUT GIVEN OVERALL CROSS VALLEY FLOW...THERE EXISTS
JUST A LOW PROBABILITY OF STRONG GUSTS TRANSLATING TO THE LOWER
ELEVATIONS. THERE DOES EXIST THE POTENTIAL FOR DEEP CONVECTIVE
ELEMENTS TO AID IN DOWNWARD TRANSPORT OF STRONGER WIND GUSTS...
BUT AT THIS POINT...THIS THREAT IS UNCERTAIN. AT THIS JUNCTURE
WILL ISSUE A WIND ADVISORY FOR THE NC/GA MTNS.

WILL PLAN ON CARRYING EMBEDDED TSTM CHANCE WHERE NAM IS PROGGING 
WEAK DESTABILIZATION...AS PER 0-3KM MUCAPE FIELD...ENCROACHING
FROM THE WEST LATE IN THE EVENING...AND PERHAPS POOLING ALONG
NWWD MOVING WEDGE BOUNDARY ACRS THE LOWER PIEDMONT. A LOW END
SVR HAIL EXISTS FOR THE NC MTNS TONIGHT ASSOCIATED WITH ELEVATED
TSTMS...ALTHOUGH THE MTNS ARE INCREASINGLY REMOVED FROM THE 
BETTER LAPSE RATES AND COOL MID-LVL TEMPS NEARER DEEP MID/UPPER
LVL CYCLONE. IT IS ALSO UNCERTAIN JUST HOW FAR NW WEAK SFC BASED
CAPE DEVELOPS TO TAKE ADVANTAGE OF IMPRESSIVE VERTICAL SHEAR TO 
PROMOTE AN ENHANCED CONVECTIVE WIND DAMAGE THREAT.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
AS OF 240 AM TUESDAY...BY 12 UTC WED THE HEART OF A 70KT LLVL JET IS 
PROGGED BY THE NAM AND GFS TO HAVE SHIFTED EAST OF THE FA...WITH 
LLVL COLD ADVECTION BEGINNING. THIS WILL PUT AN END TO PCPN BY THE 
MID MORNING HOURS. THE NAM ACTUALLY HOLDS ON TO WEAK IN SITU COLD 
AIR DAMMING MOST OF THE DAY IN A NARROW AXIS ALONG AND E OF 
INTERSTATE 85. AS THE LLVL FLOW STAYS OUT OF THE SW...THERE IS 
LIMITED DOWNSLOPE TO SCOUR THE CAD...SO THIS MAKES SOME SENSE. I 
STILL THINK IT/S A LITTLE OVERDONE AND I HAVE ALL OF THE FOOTHILLS 
AND PIEDMONT MIXING OUT BY EARLY AFTN. MODEL SOUNDINGS DON/T LOOK 
GOOD AT ALL FOR CONVECTION AS A STRONG MID LEVEL INVERSION WILL 
ALREADY BE SETTING UP AFTER 12 UTC. I KEPT A SLIGHT CHANCE OF 
CONVECTION OVER THE EXTREME SOUTH...BUT WITH THE VEERING FLOW THERE 
IS VERY LITTLE CHANCE OF ANY SEVERE STORMS THIS FAR WEST.

WHILE THE STRONGEST WINDS WILL BE NORTHEAST OF THE REGION...THE 
MIXED LAYER WILL BECOME FAIRLY DEEP BY THE AFTN HOURS. GFS BUFKIT 
SOUNDINGS SHOW 58 KTS AT THE TOP OF THE MIXED LAYER AT GSP...AND 
UPPER 40 KT WINDS MUCH LOWER IN THE SOUNDING. IF THIS WERE TO 
VERIFY...WIND GUSTS OF 40 KTS OR MORE WOULD AFFECT A GOOD BIT OF THE 
UPSTATE...NE GA AND THE SRN NC PIEDMONT. THE MTNS IN THESE 
SITUATIONS ARE ACTUALLY LESS LIKELY TO SEE STRONG WINDS AS THE 
MIXING ISN/T AS DEEP AND THE GRADIENT TENDS TO BE WEAKER WITH WSW 
ORIENTED FLOW THAN IT IS SOUTH AND EAST OF THE HIGH TERRAIN. THE NAM 
SOUNDINGS ARE NOT AS IMPRESSIVE...BUT SOME OF THIS HAS TO DO WITH 
IT/S SHALLOWER MIXED LAYER. WITH WET GROUND...GFS-LIKE WINDS WOULD 
TOPPLE NUMEROUS TREES ACROSS THE REGION...POSSIBLY RESULTING IN AN 
EVENT WITH A HIGH ENOUGH IMPACT FOR A HIGH WIND WARNING. I WON/T GO 
SO FAR AS TO ISSUE A HIGH WIND WATCH OWING TO THE MORE PESSIMISTIC 
NAM...BUT IT/S SOMETHING TO WATCH CLOSELY. 

HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION STARTING WED 
NIGHT. THIS IS A COLD HIGH WITH IT/S ORIGIN OVER SRN SASKATCHEWAN 
WHERE TEMPS RIGHT NOW ARE -20 TO -30 DEG. I SUSPECT THAT MAX TEMPS 
THU AND FRI ARE TOO WARM IN THE MOS. I DID SHAVE A COUPLE 
DEGREES...BUT DIDN/T STRAY MUCH. FRIDAY MORNING...IN 
PARTICULAR...COULD BE A COLD ONE OVER THE REGION AS THE CENTER OF 
THE HIGH WILL BE OVERHEAD. WITH THE COLD AIR WILL COME LOW 
DEWPOINTS. I/VE STAYED CLOSE TO THE MAV MOS...BUT ONCE AGAIN...AS WE 
WILL SEE SOME WEAK DOWNSLOPE ON THU AS THE HIGH CROSSES THE 
MTNS...DEWPOINTS COULD VERIFY QUITE A BIT LOWER.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 200 AM TUESDAY...STARTING AT 00Z SATURDAY...THE MEDIUM RANGE 
MODELS ARE IN BETTER AGREEMENT TONIGHT THAN LAST NIGHT BUT STILL 
HAVE SIGNIFICANT DIFFERENCES IN TIMING.  AT LEAST THE GFS AND ECMWF 
BOTH AGREE ON THE CENTER OF THE HIGH OVER THE MID ATLANTIC INITIALLY 
FRIDAY NIGHT AND GRADUALLY MOVING OUT OVER THE ATLANTIC.  THE GFS 
STILL MOVES THE LOW FASTER FROM THE NORTHERN GULF COAST TO THE 
GEORGIA/SOUTH CAROLINA COAST.  BOTH TAKE THE BULK OF THE MOISTURE 
ACROSS AREAS SOUTH OF THE MOUNTAINS.  THE INFLUENCE OF THE HIGH 
RIDGING SOUTHWEST FROM THE VIRGINIA COAST WILL CREATE TEMPERATURE 
PROFILES SUITABLE FOR MIXED WINTRY PRECIP.  IF THIS SYSTEM WERE TO 
MOVE SLIGHTLY FARTHER SOUTH WE WOULD GET EVEN LESS PRECIP.  SEEING 
THAT THERE IS VERY LITTLE NOTICEABLE CHANGE FROM PREVIOUS MODEL 
RUNS...CANNOT SEE A REASON TO CHANGE MUCH AT ALL IN THE GRID.  WEAK 
HIGH PRESSURE WILL BE IN CONTROL OF OUR WEATHER FROM LATE SUNDAY 
THROUGH MONDAY.  THE VERY END OF THE FORECAST PERIOD HAS CONTRASTING 
SOLUTIONS WITH THE GFS TAKING A SYSTEM SOUTH OF OUR FORECAST 
AREA...JUST SKIRTING OUR SOUTHERN ZONES.  THE ECMWF HAS A DEVELOPING 
LOW OVER THE LOWER MISSISSIPPI VALLEY WITH THE BULK OF THE MOISTURE 
HEADED ALMOST STRAIGHT AT US FOR TUESDAY OF NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...CAD WILL CONTINUE ACROSS THE WESTERN 
CAROLINAS THROUGH MOST OF TONIGHT. NORTHEAST WINDS WILL REMAIN 
BETWEEN 7-12 KTS ACROSS THE REGION UNTIL 10Z-12Z. CEILINGS WILL 
LOWER THIS AFTERNOON AND EVENING...REACHING LIFR BETWEEN 4Z-6Z. 
CEILINGS WILL BEGIN TO IMPROVE AROUND 12Z. FORECAST SOUNDINGS 
INDICATE THAT A LLVL JET WILL SLIDE ACROSS THE WESTERN CAROLINAS 
LATE TONIGHT AND EARLY WEDS MORNING...LIKELY CREATING A PERIOD OF LLWS 
BETWEEN 12Z-15Z. AFTER SUNRISE...SOUTHWEST WINDS WILL DEVELOP IN THE 
WAKE OF A PASSING COLD FRONT. MOMENTUM TRANSFER WITHIN MIXING LAYER 
WILL YIELD GUSTS INTO THE 20-30 KTS BY 15Z. CEILINGS AND VIS WILL 
RAPIDLY IMPROVE WITH THE PASSAGE OF THE COLD FRONT.

OUTLOOK... VFR EXPECTED WEDNESDAY THROUGH FRIDAY. A GULF COAST STORM 
SYSTEM COULD SPREAD LIGHT MIXED PRECIP INTO THE REGION FRI NIGHT AND 
SATURDAY.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST WEDNESDAY 
     FOR GAZ010-017.
NC...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EST WEDNESDAY 
     FOR NCZ033-048>053-058-059-062>065-501-503-505-507-509.
SC...NONE.

&&

$$
SYNOPSIS...BSH
NEAR TERM...NED/CSH
SHORT TERM...MCAVOY
LONG TERM...DEO
AVIATION...NED