Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 020833
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
333 AM EST MON MAR 2 2015

.SYNOPSIS...
A COLD FRONT WILL CROSS THE FORECAST AREA ON TODAY WITH ANOTHER
ROUND OF CANADIAN HIGH PRESSURE ARRIVING IN ITS WAKE. YET ANOTHER
MOIST COLD FRONT IS EXPECTED TO CROSS THE REGION WEDNESDAY AND
THURSDAY...FOLLOWED BY DRY HIGH PRESSRUE LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 305 AM...THE MOST IMMEDIATE CONCERN WILL BE THE ONGOING FOG
SITUATION...IN WHICH WE ARE SEEING WIDESPREAD 1/2-1/4 MILE VISBY
ACROSS MUCH OF THE PIEDMONT AND FOOTHILLS. A DENSE FOG ADVISORY WILL
BE ISSUED SHORTLY ROUGHLY ALONG/EAST OF HIGHWAY 25...AS VISBY WAS
IMPROVING ACROSS THE UPPER SAVANNAH RIVER VALLEY/THE WESTERN
UPSTATE...WHERE THE SURFACE GRADIENT IS A BIT MORE PRONOUNCED IN
VICINITY OF A COLD FRONT...AND THERE IS ALSO SOME INCREASING
DOWNSLOPE FLOW OFF THE HIGH TERRAIN OF NORTH GA.

OTHERWISE...PATCHY RAIN WILL CONTINUE TO PASS NEAR THE NC AND GA
MTNS EARLY THIS MORNING...BUT A DIMINISHING TREND IS EXPECTED
THROUGHOUT THE MORNING...AND POPS WILL BE MAINTAINED AT CHANCE OR
LESS THROUGH THIS TIME. OTHERWISE...WITH THE QUASI-ZONAL STATE OF
THE MID-LEVEL FLOW...COLD ADVECTION WILL BE DELAYED ACROSS MOST
AREAS OUTSIDE THE MTNS...UNTIL SURFACE HIGH PRESSURE EXPANDS ACROSS
THE CENTRAL APPALACHIANS AND MID-ATLANTIC LATER TODAY. THIS WILL
RESULT IN A BACKDOOR COLD FRONT/COLD AIR DAMMING REGIME DEVELOPING
GRADUALLY FROM NORTHEAST TO SOUTHWEST ACROSS THE CWA THIS AFTERNOON
THROUGH TONIGHT. AS SUCH...THERE WILL BE QUITE THE TEMP GRADIENT
ACROSS THE AREA THIS AFTERNOON...WITH HIGHS RANGING FROM THE LOWER
TO MID-40S ACROSS THE MTN VALLEYS OF NORTHWEST NC...TO THE LOWER 50S
ACROSS THE NORTHWEST PIEDMONT...TO 65-70 ACROSS THE LOWER SC
PIEDMONT.

WARM FRONT ACTIVATION IS EXPECTED TO OCCUR QUICKLY ACROSS THE
SOUTHEAST LATER TODAY INTO TONIGHT...AS A CYCLONE CROSSES THE
CENTRAL CONUS. UPGLIDE PRECIPITATION IS EXPECTED TO EXPAND INTO THE
FORECAST AREA THIS EVENING...WITH LIKELY POPS WARRANTED ACROSS
ROUGHLY THE SOUTHWEST HALF OF THE AREA TONIGHT. WITH TEMPS EXPECTED
TO FALL BELOW FREEZING ACROSS PORTIONS OF THE NORTHERN BLUE RIDGE...
SOME FREEZING RAIN WILL BE POSSIBLE TOWARD DAYBREAK ACROSS PORTIONS
OF THE NORTHERN NC MTNS AND FOOTHILLS. HOWEVER...IT IS NO SURE THING
THAT PRECIP WILL EXPAND THAT FAR NORTH...AND IF IT DOES QPF WILL BE
VERY LIGHT...WITH THE BULK OF RAINFALL EXPECTED TO FOCUS CLOSER TO
THE CAD FRONT ACROSS SOUTHERN PIEDMONT AREAS AND THE SC MIDLANDS.
THEREFORE...NO HEADLINES FOR FREEZING RAIN WILL BE ENTERTAINED ATTM.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AT 300 AM EST MONDAY...ON TUESDAY MORNING A POSITIVELY TILTED UPPER
TROUGH WILL EXTEND FROM HUDSON BAY TO NW MEXICO. THE TROUGHS TILT
BECOMES MORE POSITIVELY BY THURSDAY AS THE NORTHERN PORTION PROGRESSES
INTO EASTERN CANADA...WHILE THE SOUTHERN PORTION REMAINS OVER NW
MEXICO AND THE SW USA.

AT THE SURFACE...COOL HIGH PRESSURE WILL BE LODGED ALONG THE EASTERN
SEABOARD ON TUESDAY...WITH MOISTURE ISENTROPIC UPGLIDE OVER A FRONT IN
S GA PRODUCING WIDESPREAD PRECIPITATION OVER NE GA AND THE WESTERN
CAROLINAS. AT THIS POINT IT APPEAR THAT THIS WILL BE MOSTLY A RAIN
EVENT...AS THE COLDEST PART OF THE RIDGE WILL BE WELL N OF OUT AREA.
AN EXCEPTION MIGHT BE IN THE NORTHERN NC MOUNTAINS EARLY IN THE DAY.
THE SURFACE RIDGE MOVES OFFSHORE LATE TUESDAY WHILE A COLD FRONT
CROSSES THE OH AND MID MS RIVER VALLEY. THIS FRONT SLOWLY CROSSES
OUR AREA ON WEDNESDAY...FINALLY MOVING SW OF THE AREA ON WEDNESDAY
NIGHT. INSTABILITY WILL BE PRESENT AHEAD OF THE FRONT...POSSIBLE
SUPPORTING A FEW THUNDERSTORMS ON WEDNESDAY. CAPE AND SHEAR DO NOT
APPEAR TO COME INTO GOOD ALIGNMENT AT THIS TIME. BEHIND THE
FRONT...COLD ADVECTION WILL SUPPORT A CHANGEOVER TO SNOW IN THE NC
MOUNTAINS WEDNESDAY NIGHT.

THE HIGH TEMPERATURE TUESDAY WILL RUN AROUND 17 DEGREES BELOW NORMAL
IN COLD AIR DAMMING ON TUESDAY...AND THE MINIMUM TEMPERATURE AROUND
5 DEGREE ABOVE NORMAL UNDER CLOUD COVER WITH ARM ADVECTION SETTING UP
AHEAD OF THE FRONT. TEMPERATURES WEDNESDAY AND WEDNESDAY NIGHT WILL
BE AROUND 5 DEGREE ABOVE NORMAL...IN WARM ADVECTION AHEAD OF THE
FRONT...AND LINGERING CLOUD COVER ITS WAKE.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AT 300 AM EST MONDAY...ON THURSDAY MORNING A POSITIVELY TILTED UPPER
TROUGH WILL EXTEND FROM EASTERN CANADA TO NW MEXICO...WHILE A FLAT
RIDGE WILL BE CENTERED OVER THE BAHAMAS. BY FRIDAY MORNING THE
NORTHERN STREAM TROUGH PROGRESSES...ORPHANING AN UPPER LOW OVER NW
MEXICO AND THE SW USA. THE EASTERN TROUGH AMPLIFIES INTO SATURDAY...
THOUGH STILL REMAINING BROAD...WHILE THE UPPER LOW REMAINS IN NW
MEXICO. BY SUNDAY THE UPPER LOW FILLS AND THE REMAINING TROUGH
PROGRESSES OVER THE SOUTHERN PLAINS. SHORTWAVES ROUNDING THE EASTERN
TROUGH RESULTING IN SOME AMPLIFICATION EARLY MONDAY...THOUGH THE
MODELS DIVERGE ON THE TIMING OF THESE FEATURES.

AT THE SURFACE...ON THURSDAY A COLD FRONT WILL BE DEPARTING THE
AREA....WITH A TIGHT PRESSURE GRADIENT IN ITS WAKE KEEPING MOIST
UPSLOPE FLOW GOING INTO THE NC MOUNTAINS BORDERING TN. BY FRIDAY
HIGH PRESSURE SETTLE OVER THE CENTRAL APPALACHIANS...AND THE
PRESSURE GRADIENT RELAXES OVER OUR AREA. ON SATURDAY THE HIGH
SETTLES SOUTH OVER THE CAROLINAS AND GA. ANOTHER COLD FRONT RAPIDLY
CROSSES THE AREA SATURDAY NIGHT....FOLLOWED BY ANOTHER ROUND OF HIGH
PRESSURE ON SUNDAY. THERE ARE SOME INDICATIONS THAT MOISTURE MAY
SPREAD NORTH OVER THIS HIGH ON SUNDAY...BUT CONFIDENCE IS LACKING.

TEMPERATURES WILL RUN AROUND 15 DEGREES BELOW NORMAL IN COLD
ADVECTION BEHIND THE FIRST FRONT ON THURSDAY AND FRIDAY...WARMING TO
AROUND 5 DEGREES BELOW NORMAL AHEAD OF AND IMMEDIATELY BEHIND THE
SECOND FRONT ON SATURDAY AND SUNDAY.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE (EXCEPT KAVL)...VERY POOR AVIATION WEATHER
WILL PERSIST UNTIL AT LEAST SUNRISE ACROSS THE WESTERN CAROLINAS.
THE WORST CONDITIONS SHOULD BE SEEN AT KHKY/KCLT/KAND...WHERE VLIFR
CONDITIONS ARE POSSIBLE AT KCLT AND ALREADY OCCURRING AT KHKY/KAND.
CONDITIONS ARE SLIGHTLY BETTER AT KGSP/GMU...AND WITH A WESTERLY/
SOMEWHAT DOWNSLOPE FLOW IN PLACE JUST ABOVE THE SURFACE...AM
EXPECTING THIS TREND TO HOLD THROUGH THE NIGHT...ALTHOUGH LIFR
CONDITIONS WILL STILL PERSIST. TIMING OF IMPROVING CIGS AND FOG
CONDITIONS AFTER SUNRISE IS QUITE THE CHALLENGE...AS MOISTURE IS
EXPECTED TO REMAIN QUITE ABUNDANT NEAR THE SURFACE THROUGH THE DAY.
HOWEVER...CIGS SHOULD GRADUALLY LIFT TO AT LEAST MVFR AT MOST
TERMINALS BY AFTERNOON AS LIGHT WINDS TURN TOWARD THE N/NW. IN
FACT...DRIER AIR SLOWLY INFILTRATING FROM THE NORTH MAY EVEN RESULT
IN CLEARING AT KHKY DURING THE AFTERNOON. CIGS SHOULD BEGIN TO LOWER
AGAIN BY THE END OF THE PERIOD...ESP ACROSS WESTERN AREAS...AS
ANOTHER COLD AIR DAMMING EVENT BECOMES ESTABLISHED.

AT KAVL...VFR CONDITIONS PERSIST EARLY THIS MORNING...AND IT IS NOT
ENTIRELY CLEAR IF/WHEN DETERIORATION IN FLT CONDITIONS WILL OCCUR...
OR HOW RESTRICTIVE CONDITIONS WILL BECOME. THE MAIN CULPRIT IN THE
CURRENT LACK OF LOW CLOUDS/POOR VISBY APPEARS TO BE A DECENT
WESTERLY DOWNSLOPE FLOW JUST ABOVE THE SURFACE. IN ANYTHING THIS IS
EXPECTED TO GRADUALLY INCREASE THROUGH THE NIGHT...ALTHOUGH SURFACE
WINDS ARE EXPECTED TO TURN UP-VALLEY. NEVERTHELESS...THIS IS NOT
TYPICALLY A GREAT SETUP FOR IFR (OR WORSE) CONDITIONS AT KAVL...SO
HAVE GONE WITH A TREND TOWARD MVFR CONDITIONS BY 08Z. A TEMPO HAS
BEEN INCLUDED TO SUGGEST THE POTENTIAL FOR IFR CIGS (SCT008). VISBY
RESTRICTIONS ALSO REMAIN POSSIBLE. OTHERWISE...VFR CONDITIONS SHOULD
DEVELOP BY AFTERNOON...WHILE CIGS WILL LIKELY BEGIN TO LOWER AGAIN
AFTER SUNSET.

OUTLOOK...LOW CIGS AND LIGHT PRECIP/DRIZZLE WILL BE LIKELY ACROSS
MUCH OF THE AREA LATE MON NIGHT THROUGH AT LEAST TUE. A COLD FRONT
WILL MOVE SLOWLY THROUGH THE REGION WED THROUGH THURSDAY...BRINGING
CHANCES FOR HEAVIER RAINFALL TO THE AREA.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

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...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ035>037-
     056-057-068>072-082-502-504-506-508-510.
SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ007>009-
     012>014-019.

&&

$$
SYNOPSIS...JAT
NEAR TERM...JDL
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...JDL



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