Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 011908 CCA
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
257 PM EDT MON SEP 1 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 TUESDAY/...
AS OF 200 PM...A FEW SHOWERS WERE DEVELOPING OVER THE HIGHER
TERRAIN...MAINLY OVER THE SMOKIES AND SRN MOUNTAINS OF NC AND N
GEORGIA...AS ANTICIPATED BY THE CONSENSUS OF THE CONVECTION ALLOWING
MODELS. THE CONSENSUS GENERALLY FAVORS THE SMOKIES AND BALSAMS...AND
DOWNPLAYS THE CHANCES OVER THE NC PIEDMONT...SO THAT TREND WILL BE
KEPT THROUGH THE AFTERNOON. SKY COVER ALSO NEEDS TO BE ADJUSTED TO
TAKE INTO ACCT THE THICKER AREA OF HIGH CLOUDS E OF THE MTNS. NO
OTHER BIG CHANGES AS TEMPS STILL LOOK GOOD.

OVER THE NEXT 24 HOURS...THE UPPER RIDGE ACROSS THE SOUTHEAST WILL
BE FLATTENED FURTHER BY THE PASSAGE OF A SHORT WAVE UP THE OH VALLEY
LATE TONIGHT AND EARLY TUESDAY. HOWEVER...THE CLOSEST THIS FEATURE
WILL COME IS A CHUNK OF ENERGY BRUSHING PAST THE NRN MOUNTAINS THIS
EVENING. AT THAT EARLY TIME...THERE WILL BE LITTLE FOR THIS WAVE TO
WORK WITH. ALTHO IT MAY ENHANCE THE CHANCE OF CONVECTION A BIT... IT
DOES NOT LOOK LIKE WE WILL HAVE ANYTHING MORE THAN SCT/WIDELY SCT
SHOWERS AND STORMS MAINLY OVER THE HIGHER TERRAIN. THE WAVE PASSES
EARLY ENOUGH THAT ANY STORMS SHOULD DIE OFF WITH LOSS OF HEATING.
THEREAFTER...PERHAPS SOME DENSE FOG AGAIN IN SOME OF THE MOUNTAIN
VALLEYS. LOWS SHOULD BE SEASONALLY MILD AGAIN.

ON TUESDAY...STILL NOT MUCH HAPPENING AT MID LEVELS...BUT THERE
COULD BE SOME WEAK UPPER DIVERGENCE AS THE JET STREAK PASSES WELL TO
THE NORTH. THE MODELS ARE A BIT MORE ROBUST WITH CONVECTIVE PRECIP
COVERAGE OWING TO SOME IMPROVED SURFACE BASED INSTABILITY BY THE
AFTERNOON. SO...THE TREND OF HAVING A HIGHER POP FOR TUESDAY
AFTERNOON STILL LOOKS LIKE A GOOD ONE...AS DOES REACHING A FEW
DEGREES HIGHER FOR THE HIGH TEMP.

&&

.SHORT TERM /TUESDAY NIGHT 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 SUNDAY/...
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 /19Z MONDAY THROUGH SATURDAY/...
AT KCLT...A BAND OF CIRRUS WILL TRANSLATE EWD OVERHEAD THROUGH MID
AFTERNOON...BUT OTHER PATCHES OF THICKER CIRRUS REMAIN UPSTREAM AND
SHOULD MOVE THROUGH DURING THE LATE AFTERNOON. THIS WILL HELP TO
KEEP A LID ON THE DEEPER CONVECTION...SO NO VCSH IS INCLUDED. EXPECT
WIND TO REMAIN LIGHT FROM THE WSW. THE CLOUDS SHOULD THIN OUT A BIT
OVERNIGHT WITH A LIGHT SSW WIND. SOME POTENTIAL FOR FOG ACROSS THE
PIEDMONT...BUT TOO LOW TO MENTION IN THE TAF. ON TUESDAY...EXPECT A
SIMILAR SITUATION...WITH WIND COMING UP FROM THE SW AFTER THE
BOUNDARY LAYER WARMS AROUND 13Z-14Z.

ELSEWHERE...OUTSIDE OF THE MTNS WILL SEE SIMILAR CONDITIONS AS KCLT.
KAVL HAS THE ONLY OUTSIDE CHANCE OF SEEING A SHOWER OR STORM...IF
THE MODEL GUIDANCE IS CORRECT. NOT OVERLY EXCITED ABOUT THEIR
CHANCES...SO THIS IS LIMITED TO A VCTS. LATE TONIGHT...EXPECT
ANOTHER ROUND OF VALLEY FOG...AT LEAST DOWN INTO THE IFR RANGE...
AFTER 07Z. THIS COULD VERY WELL GO LIFR OR VLIFR...BUT THAT WILL NOT
BE USED IN THE FCST YET. THE FOG SHOULD BURN OFF AGAIN AROUND 13Z.

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

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-19Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  91%     MED   65%     HIGH  93%
KHKY       HIGH 100%     HIGH 100%     MED   79%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  91%     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...PM
SHORT TERM...NED
LONG TERM...JOH
AVIATION...PM








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