Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 020541
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
141 AM EDT TUE SEP 2 2014

.SYNOPSIS...
SOUTHERLY FLOW INDUCED BY A PERSISTENT BERMUDA HIGH WILL CONTINUE TO
PROMOTE DIURNAL SHOWERS AND THUNDERSTORMS THROUGH MUCH OF THE WEEK.
A FRONTAL PASSAGE WILL OCCUR ON TUESDAY EVENING INTO WEDNESDAY
MORNING WITH ANOTHER FRONT PASSING THROUGH OVER THE WEEKEND LEADING
TO ENHANCED SHOWER AND THUNDERSTORM CHANCES FOR THOSE PERIODS. HIGH
PRESSURE WILL ONCE AGAIN REGAIN CONTROL BY EARLY NEXT WEEK BEHIND
THE ABOVE MENTIONED FRONT RESULTING IN COOLER TEMPERATURES
AND MORE SETTLED WEATHER.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 140 AM...PREVIOUS FCST STILL LOOKS ON TRACK. DEBRIS CLOUDS
CONTINUE TO THIN AND MOVE EAST OVERNIGHT. STILL EXPECT ANOTHER ROUND
OF LOW CLOUDS AND FOG ACROSS THE MTN VALLEYS...WITH PATCHY FOG
ELSEHWERE. TEMPS STILL EXPECTED TO BE WELL ABOVE NORMAL.

AS OF 1030 PM EDT...MAINLY LINGERING THIN DEBRIS CLOUDS ARE EXPECTED
OVERNIGHT ACROSS THE FORECAST AREA. HOWEVER...ANOTHER ROUND OF
MORNING LOW CLOUDS AND FOG IS ANTICIPATED IN THE MOUNTAIN VALLEYS
GIVEN THAT THE AIRMASS HAS CHANGED LITTLE FROM PREVIOUS MORNINGS.
MILD MIN TEMPS SOME 5 TO 10 DEGREES ABOVE CLIMO ARE FEATURED IN LINE
WITH PERSISTENCE.

MEANWHILE...THE UPPER RIDGE ACROSS THE SE WILL BE FLATTENED FURTHER
BY THE PASSAGE OF SHORTWAVE ALONG THE OH VALLEY THROUGH TUE. THE
NUMERICAL MODELS ARE A BIT MORE ROBUST WITH CONVECTIVE PRECIP
COVERAGE ARRIVING FROM THE NW WITH ANOTHER SHORTWAVE DURING PEAK
HEATING LATE IN THE DAY...ESPECIALLY ACROSS NW NC. IMPROVED SURFACE
BASED INSTABILITY THROUGHOUT WILL THEN ALLOW SCATTERED ACTIVITY TO
RUN SOUTHEAST INTO THE PIEDMONT ON THE STRENGTH OF OUTFLOWS TUE AFTN
AND EVENING. MAXES SHOULD REACH A BIT HIGHER THAN IN PREVIOUS
DAYS...BUT WITH HEAT INDEX VALUES STILL REMAINING AROUND 100 OR LESS
IN THE WARMEST SE SECTIONS.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 2 PM MONDAY...SHORT RANGE MODELS INDICATE THAT A
WEAKENING MID LEVEL SHORT WAVE WILL RIPPLE OVER THE REGION TUESDAY
NIGHT. THE COMBINATION OF THE PASSAGE OF MID LEVEL DISTURBANCE AND
LINGERING WEAK INSTABILITY SHOULD SUPPORT ISO TO SCT SHRA/TSRA INTO
WEDNESDAY MORNING. LOW TEMPERATURES ARE FORECAST TO RANGE FROM THE
MID 60S WITHIN THE MTN VALLEYS TO THE LOW 70S EAST OF THE MTNS. ON
WEDNESDAY...MID LEVEL HEIGHTS ARE FORECAST TO SLOW RISE ACROSS THE
REGION...SOURCED FROM A RIDGE CENTERED OVER THE DEEP SOUTH. MODELS
INDICATE THAT REMNANT VORTICITY MAY LINGER ACROSS THE WESTERN
CAROLINAS THROUGH THE DAYLIGHT HOURS WEDNESDAY. FORECAST SOUNDING
SHOW WEAK TO MODERATE CAPE DEVELOPING BY MID AFTERNOON...WITH LITTLE
TO NO LLVL SHEAR. THE ENVIRONMENT SHOULD FAVOR SCT TO NUM CONVECTION
ACROSS THE RIDGES DURING THE AFTERNOON AND EVENING...WITH SCT
CONVECTION EAST. A BLEND OF FAVORED MOS SUPPORTS HIGHS FROM THE MID
80S WITHIN THE MTN VALLEYS TO LOW 90S EAST OF I-85.

ON THURSDAY...SFC HIGH PRESSURE WILL BECOME CENTERED ACROSS THE MID
ATLANTIC STATES...RESULTING IN WEAK SOUTHEAST LLVL FLOW. H5 HEIGHTS
ACROSS THE FORECAST AREA WILL LIKELY RISE ABOVE 590 DM. FORECAST
SOUNDINGS INDICATE A WEAK SUBSIDENCE INVERSION DEVELOPING DURING THE
AFTERNOON AROUND H6. AFTERNOON CAPES WILL LIKELY RANGE FROM FROM
1500-2000 J/KG ACROSS THE REGION. CIN VALUES MAY ERODE DURING THE
HEAT OF THE AFTERNOON. THE NAM LIMITS CONVECTION TO THE HIGH TERRAIN
AS THE GFS APPEARS MUCH WETTER ACROSS THE FOOTHILLS AND PIEDMONT. I
WILL TAKE A COMPROMISE OF BOTH SOLUTIONS...FORECASTING 40 TO 50 POPS
ACROSS THE MTNS TO 30 TO 40 POPS ACROSS THE FOOTHILLS AND PIEDMONT.
I WILL FORECAST HIGH TEMPERATURES 2 TO 3 DEGREES ABOVE NORMAL...BUT
SLIGHTLY COOLER THAN WED DUE TO GREATER COVERAGE OF CONVECTION.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM EDT MONDAY...AN UPPER RIDGE WILL WEAKEN OVER THE REGION
THU NIGHT INTO SAT AS THE CENTER OF H5 HIGH RETROGRADES TOWARD THE
WESTERN CONUS WHILE A NORTHERN STREAM UPPER TROUGH DIGS INTO THE
GREAT LAKES REGION. THE TROUGH IS EXPECTED TO PROGRESS EASTWARD TO
THE MID ATLANTIC STATES THRU SUN AND OFF THE EASTERN SEABOARD BY
MONDAY.

AT THE SURFACE...A BERMUDA HIGH PRESSURE WILL REMAIN IN PLACE THRU
FRI NIGHT RESULTING IN PERSISTENT MOIST S/SE FLOW AND SLIGHTLY ABOVE
NORMAL TEMPS. DESPITE THE UPPER RIDGING...MOIST PROFILE AND MODERATE
DIURNAL BUOYANCY SHOULD OVERCOME THE WEAKLY CAPPED ALOFT LEADING TO
LOW END TO SOLID CHANCE POPS FOR DIURNALLY DRIVEN CONVECTION. SAT
AND SUN...MODELS HAVE COME INTO BETTER AGREEMENT WITH THE TIMING OF
THE FROPA LATE SAT INTO EARLY SUN. THE MAIN CONCERN DURING THIS
PERIOD WILL BE HEAVY RAINFALL DUE TO THE COMBINATION OF SLOW PASSAGE
OF THE FRONT...MOIST PROFILE AND GOOD BUOYANCY. BOTH THE GFS AND
ECMWF DEPICT HEALTHY QPF RESPONSE OVER THE MTNS SAT AND OVER MUCH OF
THE CWA ON SUN. THEREFORE...HAVE UPDATED POPS TO INCREASE TO AROUND
30-50 ON SAT AND 40-60 ON SUN. MONDAY...DRIER AND COOLER CONDITIONS
EXPECTED AS THE FRONT STAYS SOUTH OF THE AREA AND A WEDGE OF SURFACE
HIGH BUILDS IN FROM THE NE. TEMPERATURES WILL REMAIN SLIGHTLY ABOVE
NORMAL THU INTO SUN AND COOLS DOWN BY 5-10 DEGREES BY MON.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...MAINLY HIGH DEBRIS CLOUDS WILL MOVE EAST OF THE AREA THRU
DAYBREAK WITH LIGHT SWLY WIND. A SCATTERED CUMULUS FIELD WILL BUILD
THROUGH THE DAY WITH HEATING AS WINDS INCREASE FROM THE SW OR WSW...
BUT SPEEDS WILL REMAIN LESS THAN 10 KT THROUGHOUT. SHORTWAVES MOVING
INTO WESTERN NC FROM THE NW LATE DAY COULD ALLOW TSRA TO MAKE A RUN
TOWARD THE PIEDMONT AGAIN...AND PROB30 FOR TSRA AFTER 21Z AND INTO
THE EVENING APPEARS WARRANTED.

ELSEWHERE...EXPECT MAINLY HIGH LEVEL DEBRIS CLOUDS OVERNIGHT...
EXCEPT FOR ANOTHER ROUND OF LOW CLOUDS AND VSBY RESTRICTIONS AT KAVL
AND ACROSS THE REST OF THE MTN VALLEYS. WILL GO AHEAD AND FEATURE
VLIFR CONDITIONS WITH THIS PACKAGE GIVEN THE MOS CONSENSUS AND
OBSERVATIONS YESTERDAY MORNING. BRIEF MVFR FOG WILL BE POSSIBLE AT
KHKY AND KAND. EXPECT CUMULUS TO BUILD WITH HEATING AND WINDS TO
REMAIN SW OR WSW THROUGH THE DAY...EXCEPT AT KAVL WHERE NW FLOW IS
EXPECTED. PROB30 FOR TSRA APPEARS WARRANTED AT ALL LOCATIONS LATE
DAY...BUT WITH THE BEST CHANCES FROM KAVL AFTER 18Z AND KHKY AFTER
20Z.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH THE REST OF
THE WEEK...BUT RESTRICTIONS ARE LIKELY EARLY EACH MORNING IN THE
MOUNTAIN VALLEYS DUE TO LOW CLOUDS AND FOG. DIURNALLY DRIVEN
SHRA/TSRA ARE EXPECTED EACH AFTERNOON AND EARLY EVENING...WITH THE
MOST COVERAGE OVER THE MOUNTAINS.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  85%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH  95%     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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JOH
NEAR TERM...HG/RWH
SHORT TERM...NED
LONG TERM...JOH
AVIATION...RWH





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