Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 300229
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1029 PM EDT MON SEP 29 2014

.SYNOPSIS...
RAINFALL WILL TAPER OFF LATER TONIGHT AND EARLY TOMORROW. DRIER HIGH
PRESSURE WILL THEN BUILD BACK OVER THE REGION ON TUESDAY AND LINGER
THROUGH THURSDAY. A COLD FRONT WILL ARRIVE FROM THE NORTHWEST ON
FRIDAY WITH A COOL AND DRY AIR MASS MOVING BACK INTO THE REGION OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 1025 PM...PRECIP HAS MOVED EAST OF THE AREA AND SKIES ARE
SLOWLY CLEARING. THIS IS ALLOWING FOG AND LOW CLOUDS TO FORM. ALMOST
A CERTAINTY NOW THAT AREAS OF DENSE MTN VALLEY FOG WILL FORM
OVERNIGHT. HOWEVER...EVEN WITH THE FOG DEVELOPING OUTSIDE OF THE
MTNS...IT IS STILL UNCLEAR WHETHER DENSE FOG OR LOW CLOUDS WILL WIN
OUT. EVEN IF THE LOW CLOUDS ARE PREDOMINANT...THERE WILL LIKELY BE
PATCHY DENSE FOG IN THE NORMALLY MORE FOGGY AREAS...ESPECIALLY NEAR
BODIES OF WATER. WILL UPDATE THE HWO FOR NOW AND LET THE NEXT SHIFT
ISSUE A DENSE FOG ADV IF IT BECOMES MORE THAN PATCHY.

AS OF 750 PM...ISOLATED LIGHT SHRA OR SPRINKLES WILL MOVE EAST OF
THE AREA THIS EVENING LEAVING A DRY FCST. GUIDANCE CONTINUES TO
INCREASE THE PROBABILITY OF DENSE MTN VALLEY FOG OVERNIGHT. WILL KEEP
THE HWO MENTION FOR THE POTENTIAL. GUIDANCE IN LESS AGREEMENT ON FOG
POTENTIAL OUTSIDE OF THE MTNS. SOME GUIDANCE SUGGESTING LOW CLOUDS
REDEVELOP IN THE LINGERING LOW LEVEL MOISTURE AND THE LOWER LEVELS
REMAIN MIXED...WHILE OTHERS SHOW A DECOUPLING ATMOS WITH FOG
FORMING. EXPECT THE BEST CHC OF FOG WILL BE THE NORMALLY MORE FOGGY
AREAS NEAR BODIES OF WATER...WHILE OTHER AREAS SEE ONLY PATCHY FOG
DENSE FOG WITH LOW CLOUDS FORMING. WILL HAVE TO KEEP AN EYE ON THESE
DEVELOPMENTS OVERNIGHT. HAVE UPDATED THE FORECAST FOR THESE FEATURES
AND FOR CURRENT CONDITIONS.

AS OF 430 PM...WIDESPREAD PRECIP BEGINNING TO SLIDE EAST OF THE
AREA. HOWEVER...NUMEROUS LIGHT SHRA LINGER OUTSIDE OF THE MTNS.
LATEST GUIDANCE SUGGESTS THE SHRA WILL CONTINUE TO MOVE EAST AND OUT
OF THE AREA...BUT SLOWLY THE REST OF THE AFTERNOON...THEN MORE
QUICKLY THIS EVENING. ALL REMAINING PRECIP WILL BE VERY LIGHT. DO
NOT EXPECT ANY TSRA THIS AFTERNOON GIVEN THE COOL AND CLOUDY
CONDITIONS AND THE OBSERVED WEAK INSTABILITY. HAVE LOWERED TEMPS AND
RAISED DEWPOINTS IN LINE WITH LATEST OBS...ALONG WITH SKY AND WINDS.

AT 200 PM EDT MONDAY...AN UPPER TROUGH AXIS WILL CROSS THE SOUTHERN
APPALACHIANS THIS AFTERNOON...AND MOVE OFF THE COAST BY LATE
TUESDAY. MEANWHILE...AND UPPER RIDGE WILL PROGRESS FROM THE PLAINS
TO THE MS RIVER VALLEY. A SHORTWAVE ROUNDING THE BASED OF THE TROUGH
WAS PROVIDING SUPPORT FOR WIDESPREAD LIGHT RAIN IN THE
PIEDMONT....WHILE ANOTHER WAS PRECEDED BY A BAND OF SHOWERS NEAR THE
BLUE RIDGE. ALTHOUGH THE ACTIVITY IN THE WEST IS MUCH MORE
LIMITED...INSTABILITY WILL BE GREATER IN THE MOUNTAINS DUE TO
LESSENING CLOUD COVER...AND ISOLATED TO SCATTERED THUNDERSTORMS
CANNOT BE RULED OUT THERE.

DRYING FROM ALOFT IS EXPECTED BEHIND THE PAIR OF SHORTWAVES THIS
AFTERNOON...WHILE PRECIPITATION DIMINISHES ACROSS THE AREA. WINDS
ARE EXPECTED TO BE QUITE LIGHT LATE THIS AFTERNOON AND OVERNIGHT...
AND MODEL GUIDANCE IS SUPPORTIVE OF FOG ACROSS MOST OF THE AREA...
WITH DENSE FOG QUITE POSSIBLE IN THE NC MOUNTAIN VALLEYS. ALTHOUGH
MODEL TIME HEIGHTS SHOW SOME MOISTURE LINGERING THE LOWER LEVELS...
CLOUD COVER IS EXPECTED TO BE LIMITED. MINIMUM TEMPERATURES ARE
EXPECTED TO RUN AROUND NORMAL.

ON TUESDAY...WITH ONLY LIGHT WINDS EXPECTED TO COME UP FORM THE
NE...MORNING FOG MAY TAKE SOME TIME TO BURN OFF. WINDS WILL
GRADUALLY VEER FROM TO THE SE DURING THE DAY...REMAINING LIGHT. WITH
MORE SUNSHINE AND RISING HEIGHTS ALOFT...HIGH TEMPERATURES ARE
EXPECTED TO RUN SEVERAL DEGREES ABOVE NORMAL. PRECIPITATION IS NOT
EXPECTED ON TUESDAY DUE TO THE DRIER AIR MASS...AND A WARM NOSE
ALOFT BETWEEN 600 AND 400 MB.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 215 PM MONDAY...AN UPPER RIDGE IS FORECAST TO BUILD ACROSS THE
EASTERN U.S. DURING THE MIDWEEK TIMEFRAME IN RESPONSE TO A
SIGNIFICANT UPPER TROUGH DIGGING SOUTH THROUGH THE ROCKIES. SURFACE
HIGH PRESSURE INTIALLY OVER THE WESTERN GREAT LAKES IS FORECAST TO
RIDGE SOUTHWARD OVER THE REGION. THIS WILL PROVIDE A WARM AND
GENERALLY DRY STRETCH OF WEATHER THROUGH THURSDAY. THE EXCEPTION MAY
BE OVER PORTIONS OF THE MOUNTAINS WHERE UPSLOPE FLOW MAY TRIGGER
SOME ISOLATED SHOWERS EACH AFTERNOON. TEMPERATURES WILL BE ABOVE
CLIMO THROUGH THU.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 210 PM MONDAY AFTERNOON...THE MEDIUM RANGE FCST PICKS UP AT 00Z
ON FRIDAY WITH WEAK UPPER RIDGING IN PLACE OVER THE SE REGION AND A
FAIRLY POTENT LOOKING SOUTHERN STREAM UPPER SHORTWAVE DIGGING DOWN
OVER THE SOUTHERN PLAINS. OVER THE NEXT 24HRS...THE SHORT IS
EXPECTED TO MOVE ACROSS THE FCST AREA AND SIMULTANEOUSLY BECOME
ABSORBED BACK INTO THE NORTHERN STREAM UPPER TROF. BEYOND THIS
POINT...THE LONG RANGE MODELS STILL DIFFER WRT THE EVOLUTION OF THE
MAIN UPPER TROF. THE ECMWF REAMPLIFIES THE TROF MULTIPLE TIMES FROM
SAT THRU EARLY NEXT WEEK AND KEEPS THE TROF AXIS ORIENTED TO OUR
NORTH. ON THE OTHER HAND...THE LATEST RUN OF THE GFS MAINTAINS A
MUCH BROADER LONGWAVE TROF OVER THE EASTERN CONUS THRU NEW DAY 7.

AT THE SFC...WARM SLY LOW LVL FLOW WILL BE IN PLACE AT THE START OF
THE PERIOD EARLY FRI. OVER THE NEXT 12 TO 24 HRS...A ROBUST COLD
FRONT WILL MOVE OVER THE CAROLINAS AND SHOULD MOVE OFF THE CAROLINA
COAST BY SAT MORNING. IT ITS WAKE...COOL AND DRY HIGH PRESSURE WILL
SPREAD OVER THE CWFA AND REMAIN THRU THE WEEKEND. THE MODELS ARE
SUGGESTING THAT ANOTHER LOW WILL DEVELOP OVER THE GREAT LAKES EARLY
NEXT WEEK AND MOVE A SECOND COLD FRONT OVER OUR AREA. AT THIS POINT
HOWEVER...THE TIMING BETWEEN MODELS IS INCONSISTENT AND THEY SUGGEST
THAT THE FROPA WILL BE ESSENTIALLY DRY. AS FOR THE SENSIBLE FCST...I
STEADILY RAMP POPS UP FORM WEST TO EAST ON FRI WITH THE HIGHEST
VALUES BETWEEN ROUGHLY 12Z AND 18Z. BY 12Z SAT...POPS DROP BACK
BELOW 20% FOR MOST OF THE CWFA. THE REST OF THE MEDIUM RANGE SHOULD
BE DRY. TEMPS WILL COOL AFTER THE FROPA WITH HIGHS IN THE LOW 70S
OVER THE WEEKEND FOR THE LOWER ELEVATIONS AND LOWS IN THE LOWER TO
MID 50S.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT...A FEW -SHRA POSSIBLE THIS EVENING...BUT VFR CIGS SHUD
SLOWLY SCATTER OUT OVERNIGHT AS DEEP MOISTURE MOVES EAST. LOW LEVEL
MOISTURE LINGERS INTO THE MORNING TUE. GUIDANCE DIFFERS ON WHETHER
THE DEVELOPING MVFR RESTRICTIONS WILL BE VSBY OR CIGS. HAVE KEPT
CONSISTENCY AND GONE WITH MVFR FOG AND SCT MVFR CLOUDS FROM LATE
TONIGHT THRU EARLY TUE MORN. IF CIGS DEVELOP...THEY COULD LINGER
THRU NOON BEFORE SCATTERING OUT WHILE FOG ENDS EARLIER. LIGHT NNE
WIND BECOMES CALM OVERNIGHT WITH LIGHT NLY WIND DEVELOPING TUE. ANY
CLOUDS TUE AFT WILL BE VFR.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT OUTSIDE OF THE MTNS...EXCEPT
BETTER CHC OF RESTRICTIONS. HAVE DROPPED KHKY AND KAND TO IFR AS
THEY USUALLY HAVE MORE RESTRICTIONS THAN KGSP/KGMU. KAVL LOOKS TO
SEE VLIFR OVERNIGHT AS FCST SOUNDINGS AGREE WITH THE POTENTIAL IN
THE MOS GUIDANCE. RESTRICTIONS SHUD BE GONE BY MID MORNING...BUT SCT
LOW CLOUDS COULD LINGER THRU NOON. VFR EXPECTED TUE AFTERNOON WITH
LITTLE CHC OF MTN CONVECTION WITH THE CAPPED ATMOS. LIGHT WIND THRU
THE PERIOD.

OUTLOOK...VFR CONDITIONS WILL PREVAIL WED THROUGH FRIDAY MORNING...
WITH FOG/VSBY CONCERNS REMAINING ACROSS THE MTNS AND FOOTHILLS EARLY
EACH MORNING. A FRONT WILL APPROACH ON FRIDAY WHICH COULD TRIGGER
SOME SHOWERS AND THUNDERSTORMS...WITH ASSOCIATED RESTRICTIONS
POSSIBLE.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH  89%     HIGH  80%     HIGH  81%     HIGH 100%
KGSP       MED   75%     MED   68%     MED   78%     HIGH 100%
KAVL       MED   74%     MED   71%     HIGH  86%     HIGH 100%
KHKY       HIGH  82%     MED   77%     HIGH  85%     HIGH 100%
KGMU       MED   78%     MED   65%     MED   78%     HIGH 100%
KAND       MED   66%     MED   75%     MED   78%     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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...JAT/RWH
SHORT TERM...LG
LONG TERM...JPT
AVIATION...RWH





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