000
FXUS62 KGSP 062005
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
305 PM EST THU MAR 6 2014

.SYNOPSIS...
A COASTAL LOW WILL STRENGTHEN AND MOVE FROM FLORIDA UP THE ATLANTIC
COAST TONIGHT AND FRIDAY.  DRIER AND WARMER HIGH PRESSURE IS THEN
EXPECTED TO RETURN TO OUR REGION THIS WEEKEND AND PERSIST THROUGH
EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
THE WINTER WEATHER ADVISORY HAS BEEN UPGRADED TO A WARNING ALONG THE
EASTERN BLUE RIDGE IN NORTH CAROLINA...AND ALONG THE I-40 CORRIDOR
EAST OF THE MTNS...WITH A NEW WINTER WX ADVISORY POSTED FOR THE I-85
CORRIDOR IN NORTH CAROLINA.

EXTENSIVE HIGH CLOUDS AND DECENT LOW LEVEL CAA HAS RESULTED IN TEMPS
REMAINING QUITE CHILLY ACROSS MUCH OF THE AREA THIS AFTERNOON
(EXCEPT FOR THE EXPOSED AREAS OF THE SOUTHWEST NC MTNS...WHERE TEMPS
ARE NEAR 50 THIS PM)...AND MOST AREAS HAVE NOT MANAGED TO ESCAPE THE
30S. AS A RESULT...MODEL GUIDANCE IS TOO WARM IN COMPARISON TO
OBSERVED WET BULB TEMPS...WHICH IS NOT A GOOD SIGN. PRECIP
ASSOCIATED WITH ONGOING NE GMEX CYCLOGENESIS EXTENDS FROM NORTHERN
ALABAMA TO THE I-85 CORRIDOR IN SC...AND WILL CONTINUE TO OVERSPREAD
THE FORECAST AREA THROUGH THE AFTERNOON/EVENING. BASED UPON WET BULB
TEMPS...IT APPEARS THAT MOST AREAS SOUTH OF I-85 WILL SEE MOSTLY
RAIN THROUGH MUCH OF THE EVENING...WITH PERHAPS SOME SLEET THROWN IN
AS TEMPS WET BULB BELOW 40. IN FACT...MOST PORTIONS OF THE FORECAST
AREA WILL SEE PRECIP BEGIN AS RA OR A RA/SLEET MIX.

THE FUN BEGINS LATER THIS EVENING INTO THE OVERNIGHT...AS THE
SURFACE LOW BEGINS TO DEEPEN OFF THE SOUTHEAST COAST...STRENGTHENING
THE DAMMING RIDGE AND INCREASING ADVECTION OF COLD/LOW WET BULB
SURFACE AIR INTO THE FORECAST AREA. THE NAM REMAINS AN OUTLIER IN
DEVELOPING A VERY PROMINENT WARM NOSE (OF +5 TO +6) IN THE 3-5 KFT
LAYER THIS EVENING...AS EASTERLY FLOW ACCELERATES (TO 70-80 KTS)
ABOVE THE COLD DOME NORTH OF THE DEVELOPING CYCLONE. MEANWHILE...THE
GFS AND ECMWF...BOTH FEATURING A MORE /OFF-COAST/ SURFACE LOW
TRACK...DEVELOP VERY LITTLE IN THE WAY OF A WARM NOSE...CERTAINLY
ONE THAT WOULD SUGGEST MORE OF A SLEET THAN A FREEZING RAIN CONCERN.
WE REMAIN QUITE SKEPTICAL OF THE NAM...AS THE WINDS/ADVECTION
PATTERNS SEEM OVERDONE...AND FEEL THAT WAA WILL HAVE DIFFICULTY
OVERWHELMING COOLING INDUCED BY INTENSE UVV IN THIS LAYER. IN
ADDITION...THIS IS NOT A CLIMATOLOGICALLY FAVORED TIME OF YEAR FOR
ICE STORMS. HOWEVER...THERE ARE ENOUGH MEMBERS OF THE SREF ENSEMBLE
SUPPORTING THE OP NAM THAT I/M NOT PREPARED TO ELIMINATE IT
ALTOGETHER. THEREFORE...THE FORECAST IS LARGELY BASED UPON A BLEND
OF PARTIAL THICKNESS GUIDANCE WITH A BLEND OF THE GFS AND NAM (BUT
WEIGHTED TOWARD THE GFS). THIS RESULTS IN MAINLY A SLEET/SNOW
SCENARIO ALONG THE BLUE RIDGE...WITH A SLEET/FZRA SITUATION OVER THE
NORTHWEST PIEDMONT.

TOTAL ACCUMS OF SLEET/SNOW ARE EXPECTED TO RANGE FROM 2-6 INCHES
ALONG THE BLUE RIDGE. HOWEVER...MUCH WILL DEPEND UPON HOW MUCH SLEET
FALLS VS THE AMOUNT OF SNOW...AND THE FORECAST IS GENERALLY BASED
UPON AN EXPECTATION OF ABOUT 50/50 SNOW AND SLEET. MORE SNOW THAN
SLEET WOULD EQUATE TO QUITE A BIT MORE SNOWFALL ACCUM. OVER THE NW
PIEDMONT...WILL FORECAST AROUND A HALF INCH OF SLEET ALONG WITH A
QUARTER INCH OF ICE...BUT LATEST GUIDANCE TRICKLING IN SUGGESTS WE
MAY SEE MORE SLEET THAN ICE IN THESE AREAS. MEANWHILE...AROUND A
TENTH OF AN INCH OR SLEET/ICE IS EXPECTED ACROSS THE SOUTHERN NC
FOOTHILLS AND PIEDMONT.

AS THE CYCLONE MOVES UP THE COAST FRI MORNING...THE COLD DOME WILL
BEGIN TO DRAIN...ALLOWING PRECIP TO CHANGE TO ALL RAIN AS THE UPPER
LOW PASSES SOUTH AND EAST OF THE AREA...AND DEFORMATION ZONE PRECIP
REMAINS WRAPPED INTO THE AREA INTO THE EARLY AFTERNOON.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AT 230 PM EST THURSDAY...THE UPPER LOW AND ASSOCIATED SURFACE
CYCLONE WILL BE OFF THE CAROLINA COAST AT THE BEGINNING OF THE PERIOD
AND WILL MOVE QUICKLY NE AWAY FROM THE AREA FRIDAY NIGHT. THIS WILL
ALLOW UPPER HEIGHTS TO QUICKLY BUILD OVER THE REGION FRIDAY NIGHT. A
FLAT UPPER RIDGE WILL THEN PERSIST OVER THE SE U.S. THROUGH SUNDAY.
A SHORT WAVE MOVING THROUGH THE NORTHERN STREAM WILL PUSH A WEAK
BACKDOOR COLD FRONT INTO THE AREA ON SUNDAY.

IN REGARD TO SENSIBLE WEATHER...CLOUDS WILL QUICKLY PULL OUT TO THE
EAST FRIDAY NIGHT AS SURFACE HIGH PRESSURE BUILDS EAST OVER THE
AREA. GENERALLY CLEAR CONDITIONS WILL PERSIST THROUGH SATURDAY. AS THE
WEAK FRONT APPROACHES...CLOUDS WILL BE ON THE INCREASE EARLY SUN.
HOWEVER...WITH DOWNSLOPE FLOW ON SUNDAY A MIX OF SUN AND CLOUDS
LOOKS TO BE A GOOD BET. CAN`T COMPLETELY RULE OUT SOME LIGHT SHOWERS
REACHING THE MOUNTAIN COUNTIES ADJACENT TO TENNESSEE ON SUNDAY AS
THE FRONT ARRIVES. HOWEVER...THE CHANCE FOR MEASURABLE PRECIP APPEARS
TO BE LESS THAN 30 PERCENT.

THE BIG STORY WILL BE THE WARM UP WHICH WILL COMMENCE ON SAT. LOW
LEVEL THICKNESS SUPPORTS MAX TEMPS OF 65 TO 70 BOTH SAT AND SUN
OUTSIDE THE MOUNTAINS...WITH 60S IN THE MOUNTAINS. THIS LOOKS
REASONABLE CONSIDERING THE GENERAL DOWNSLOPE FLOW THAT WILL
PREVAIL.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 205 PM THURSDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
MONDAY WITH A WEAK SHORTWAVE PASSING ACROSS OUR AREA SUNDAY EVENING.
WE WILL THEN BE UNDER THE INFLUENCE OF A LOW AMPLITUDE UPPER RIDGE
CENTERED OVER THE EASTERN GULF INTO MONDAY. LOW LEVEL WIND DIRECTION
TO START THE WEEK WILL REMAIN GENERALLY FROM THE WEST.

THE NEW GFS RUN IS FAIRLY DIFFERENT FROM THE PREVIOUS WITH A SHORTER
DURATION OF PRECIP IN MID WEEK.  ALL MODELS KEEP OUR REGION EITHER
DRY OR ALMOST DRY THROUGH AT LEAST MONDAY NIGHT. THE GFS HAS A CUT
OFF 500MB LOW OVER SW TEXAS AT 12Z MONDAY WHICH TRACKS TO CORPUS
CHRISTI AT 12Z TUESDAY AS IT OPENS UP. THE ECMWF HAS A SOMEWHAT
SIMILAR FEATURE. BOTH MODELS BRING THIS SHORTWAVE WITH
ACCOMPANYING SURFACE LOW OVER OUR AREA TUESDAY NIGHT INTO WEDNESDAY.
ALMOST NO INSTABILITY AS THE MAIN FEATURE COMES OVER WED MORNING.
BIG DIFFERENCE BETWEEN THE MODELS IS THE BROAD UPPER TROUGH MOVING
IN BEHIND THE INITIAL SHORTWAVE IS DRY ON THE GFS BUT HAS A LOW TO
FORM ON THE INFLECTION POINT OF THE DEEPER ECMWF TROUGH. THE EC
ACTUALLY HAS THE FIRST FEATURE WRAPPING INTO AND MERGING WITH THE
BIGGER TROUGH MOVING SE. THE TROUGH AND THE SURFACE LOW ON THE EC
MERGE AND BOTH SWING NE WITH MOST ENERGY MOVING NORTH OF OUR
FORECAST AREA. THE GFS ENDS ALL PRECIP OVER OUR AREA BEFORE MIDNIGHT
WED NIGHT AND THE EC ENDS THE WRAP AROUND NW FLOW PRECIP FOR THE NRN
MTNS OF NC THURSDAY AFTERNOON. ALL PRECIP SHOULD BE RAIN AS WE
EXPECT PRECIP TO MOVE EAST OF AREA BEFORE COLDER AIR FILTERS IN BUT
MAY BE BRIEF TRANSITION TO SNOW AS IT ENDS FOR THE NC MTNS. TRENDS
ARE THAT TEMPERATURES IN THE WAKE OF THE DEPARTING LOW AND UNDER THE
UPPER TROUGH WILL BE COOLER THAN PREVIOUSLY FORECAST. TEMPERATURES
EARLY IN THE WEEK BEING ABOVE NORMAL AND DROPPING TO BELOW NORMAL
UNDER THE UPPER TROUGH AND COOL AIR ADVECTION BEHIND THE SURFACE LOW.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
AT KCLT...VFR CONDITIONS WILL CONTINUE THROUGH THE REMAINDER OF THE
AFTERNOON AND EARLY EVENING HOURS AS MOISTURE SPREADS ACROSS THE
REGION FROM THE SOUTH.  EXPECTING -RA TO MOVE INTO THE AREA BY
MID/LATE AFTERNOON WITH A POTENTIAL FOR A WINTRY MIX AT ONSET.
THUS...WENT WITH TEMPO FROM 19-23Z WITH AN MVFR VISB AND -RAPL.  AT
23Z PREVAILED -RA BR WITH AN MVFR VISB AND A LOW VFR CIG.
ISENTROPIC ASCENT WILL RAMP UP FURTHER BY LATE EVENING LEADING TO
CIGS DROPPING TO IFR LEVELS WITH A PREDOMINATE -RA PTYPE.  AS
TEMPERATURES COOL DIURNALLY BY EARLY MORNING...A BRIEF WINDOW OF
FZRA IS POSSIBLE AS LOW TEMPERATURES AT THE SURFACE FALL TO FREEZING
LEVELS.  TEMPERATURES ARE EXPECTED TO WARM BY LATE MORNING LEADING
TO AN ALL RA TRANSITION LASTING THROUGH THE END OF THIS TAF CYCLE.
WINDS THROUGH THE PERIOD WILL BE RATHER STRONG AS THE CAD BUILDS IN
FROM THE NORTHEAST.  THUS...EXPECTING NE WINDS SUSTAINED AROUND THE
15KTS MARK WITH GUSTS NEARING 25KTS BY EARLY MORNING.

AT KAVL...EXPECTING SLIGHTLY IMPROVED CONDITIONS FROM THAT OF SITES
TO THE EAST.  INITIALIZED TAF WITH ENE WINDS AT AROUND 11KTS UNDER
BKN HIGH LEVEL CIGS.  EXPECTING PRECIPITATION TO MOVE INTO THE
REGION AROUND THE 20-21Z TIME FRAME IN THE FORM OF A WINTRY MIX WITH
-RAPL PREVAILING.  AT THAT TIME..VISB WILL LOWER TO MVFR LEVELS WITH
CIGS HOLDING AT LOW END VFR.  BY EARLY EVENING...THERMAL PROFILES
SUPPORT A CHANGEOVER TO -SNPL WITH CIGS AND VISBS LOWERING TO MVFR
LEVELS WITH WINDS BACKING SLIGHTLY TO THE NORTH AT AROUND 8-10KTS.
THESE CONDITIONS WILL PREVAIL THROUGH THE MID MORNING WHEN
TEMPERATURES WARM THROUGH THE COLUMN TO LEVELS NOT SUPPORTIVE OF
WINTRY PRECIPITATION...THUS WENT WITH A PTYPE CHANGEOVER TO ALL RA AT
AROUND 10Z UNDER MVFR CIG/VISB RESTRICTIONS.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE WITH VFR CONDITIONS
PREVAILING THROUGH THE LATE AFTERNOON BEFORE MOISTURE SPREADS IN THE
FROM THE SOUTH AS ISENTROPIC ASCENT RAMPS UP AHEAD OF THE
APPROACHING SURFACE CYCLONE.  CONDITIONS WILL DETERIORATE AT ALL
SITES FROM VFR TO MVFR...BEFORE BOTTOMING OUT AT IFR LEVELS AS
PRECIPITATION SHIELD OVERSPREADS THE REGION.  PTYPES WILL LIKELY BE
MIXED EARLY ON AT KGSP...KGMU...AND KHKY WHILE KAND SHOULD STAY
PREDOMINATELY RA.  OVERNIGHT...PTYPES WILL TRANSITION TO RA AT ALL
SC SITES WITH A WINTRY MIX REMAINING LIKELY AT KHKY WHERE TAF
HIGHLIGHTS SN...PL...AND FZRA.  AS FOR CIGS AND VISBS...EXPECTING
IFR RESTRICTIONS TO PREVAIL THROUGH MID MORNING BEFORE LIFTING TO
MVFR LEVELS THROUGH THE REMAINDER OF THE PERIOD AS THE MOISTURE
PLUME EJECTS TO THE NORTHEAST.  WINDS WILL BE STRONG OVERNIGHT AT
ALL SITES WILL SUSTAINED NE WINDS OF AROUND 15-20KTS POSSIBLE WITH
GUSTS NEARING 25-30KTS...ESPECIALLY AT THE SC SITES.

OUTLOOK...IFR/MVFR FLIGHT RESTRICTIONS AND PRECIPITATION COVERAGE
WILL CONTINUE INTO FRI MORNING...WITH PRECIP POSSIBLY LINGERING
THROUGH FRIDAY AFTN AS LOW PRESSURE PULLS AWAY ALONG THE EAST COAST.
THE BEST CHANCE OF FREEZING/FROZEN PRECIPITATION WILL BE ACROSS THE
NC PIEDMONT THROUGH MIDDAY FRI. DRY HIGH PRESSURE AND IMPROVING
CONDITIONS ARE EXPECTED THROUGH SAT...WITH A DRY COLD FRONT CROSSING
ON SUNDAY.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       MED   74%     LOW   54%     LOW   56%     MED   65%
KGSP       MED   61%     LOW   48%     LOW   41%     MED   65%
KAVL       HIGH  83%     HIGH  81%     MED   73%     HIGH  91%
KHKY       HIGH  96%     LOW   58%     MED   66%     HIGH  83%
KGMU       MED   67%     LOW   47%     LOW   38%     MED   65%
KAND       MED   66%     MED   62%     MED   64%     MED   77%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
     FRIDAY FOR NCZ048-052-059-063-068>072-508-510.
     WINTER STORM WARNING FROM 7 PM THIS EVENING TO NOON EST FRIDAY
     FOR NCZ033-035>037-049-050-053-056-057-064-065-501>507-
     509.
SC...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
     FRIDAY FOR SCZ003.

&&

$$
SYNOPSIS...DEO
NEAR TERM...JDL
SHORT TERM...LG
LONG TERM...DEO
AVIATION...CDG