Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 061717
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
117 PM EDT WED MAY 6 2015

.SYNOPSIS...
WEAK HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH THURSDAY...
AS LOW PRESSURE ORGANIZES OFF THE SOUTHEAST COAST. THERE IS MUCH
UNCERTAINTY ABOUT THE TRACK OF THE LOW PRESSURE OFF THE SOUTHEAST
COAST ON FRIDAY AND THROUGH THE WEEKEND...AS TO WHETHER OR NOT IT
REMAINS OFFSHORE OR MOVES INLAND OVER THE COASTAL PLAIN OF THE
CAROLINAS. THE LOW WILL MOVE VERY SLOWLY AND MAY NOT DEPART TO THE
EAST UNTIL MONDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 1 PM...BUMPED MAX TEMPS UPWARD A COUPLE DEGREES BASED ON
CURRENT TRENDS. LOW POPS STILL LOOK GOOD ALONG THE TN/NC BORDER
WHERE BEST INSTABILITY EXISTS.

AS OF 945 AM...GENERALLY CLEAR ACROSS THE AREA ALLOWING TEMPS TO
SPIKE  UPWARD QUICKLY... ESPECIALLY OUTSIDE THE MOUNTAINS.
THEREFORE...ADJUSTED TEMP TRENDS. LATEST HRRR NOT EXCITED AT ALL
ABOUT CONVECTIVE CHANCES IN THE MOUTAINS THIS AFTERNOON. MID LEVEL CAP
LOOKS TOO STRONG TO OVERCOME EXCEPT PERHAPS OVER THE HIGHEST TERRAIN
ALONG THE TN BORDER. BLENDED IN LATEST CONSHORT INTO POP GRID WHICH
TAMPED POPS DOWN TO AREAS OF ABOUT 20% ALONG THE TN BORDER IN
WESTERN NC.

AS OF 810 AM...DID A QUICK UPDATE MAINLY TO CAPTURE LATEST HOURLY
TEMP TREND. OTHERWISE FORECAST ON TRACK.

AS OF 620 AM EDT WEDNESDAY...CALM WINDS UNDER MOSTLY CLEAR SKIES
THIS MORNING ACROSS MUCH OF THE FCST AREA.  ALTHOUGH THINNING
SOMEWHAT...STILL SEEING SOME PATCHY HIGH LEVEL CIRRUS ACROSS THE
EASTERN MOST ZONES PER IR SAT.  AS PREVIOUSLY FCST...VISB
RESTRICTIONS DUE TO PATCHY DENSE FOG ARE EVIDENT IN AND AROUND THE
LITTLE TN RIVER VALLEY...WITH IMPROVEMENT FCST AFTER SUNRISE.
OTHERWISE...NO CHANGES NEEDED/MADE TO THE FCST WITH THIS UPDATE.

PREVIOUS DISCUSSION...

AS OF 300 AM EDT WEDNESDAY...THE UPPER PATTERN THIS MORNING CONSISTS
OF AN UPPER TROF ATOP THE SOUTHERN ROCKIES WITH A SERIES OF SHORT
WAVE IMPULSES SLIDING THROUGH THE TROF BASE OVER THE OK/TX PANHANDLE
REGION.  FURTHER EAST...SHARP UPPER RIDGE AXIS CONTINUES TO SLOWLY
SLIDE ACROSS THE SOUTHEASTERN UNITED STATES WHILE A CLOSED LOW
CONTINUES TO DEEPEN OFF THE SOUTH FLORIDA COASTLINE.  AT THE
SURFACE...HIGH PRESSURE OFF THE CAROLINA COAST WILL CONTINUE TO
ELONGATE/ERODE AS A SURFACE DISTURBANCE BENEATH THE ABOVE MENTIONED
FLORIDA COASTAL H5 LOW SLIDES NORTHWARD.  IN RESPONSE...PRIMARY
SOUTHERLY MOISTURE FETCH THAT HAS BEEN IN PLACE OVER NORTHEAST GA
AND THE WESTERN CAROLINAS WILL GIVE WAY TO BACKED SURFACE FLOW.
UPPER LEVEL MOISTURE STREAMING IN ALOFT WILL LEAD TO SCATTERED
CIRRUS/CIRROSTRATUS THROUGHOUT THE DAY...THUS PARTLY/MOSTLY CLOUDY
SKIES ARE FEATURED IN THE FCST.  AS FOR POPS...MODEL OUTPUT IS
RATHER UNIMPRESSIVE WILL LITTLE INSTABILITY AVAILABLE FOR
CONVECTION...THUS ONLY ISOLATED/SCATTERED SHRA AND OR TSRA IS
MENTIONED ACROSS THE HIGH TERRAIN.  THEREFORE NORTHEAST GA ALONG
WITH THE NC/SC PIEDMONT REGIONS WILL REMAIN DRY WITH HIGHS TOPPING
OUT IN THE LOWER 80S.  ALL POPS WILL FALL OFF THIS EVENING AS
HEATING IS LOST...WITH PARTLY CLOUDY SKIES PREVAILING THROUGH THE
REMAINDER OF THE PERIOD.  LOWS ON THURSDAY MORNING WILL REMAIN
GENERALLY 3-5 DEGREES ABOVE CLIMO AS NOCTURNAL SKY COVER LIMITS
RADIATIONAL COOLING.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 245 AM WEDNESDAY...THE OBVIOUS CONCERN WITH THE LATER PART OF
THE WEEK CONTINUES TO BE THE FATE OF LOW PRESSURE THAT IS EXPECTED
TO HAVE DEVELOPED/ORGANIZED OFF THE SOUTHEAST COAST BY THURSDAY
MORNING. THE MODELS SEEM TO BE IN BETTER AGREEMENT...BUT SMALL
DIFFERENCES IN THE FCST TRACK OF THE LOW WILL HAVE SOME IMPACT ON
THE PRECIP CHANCES OVER THE ERN ZONES. THE FCST GENERALLY LEANS
TOWARD THE ECMWF WITH ITS KEEPING THE LOW CENTER OVER THE GULF
STREAM A BIT LONGER...AND AWAY FROM THE GFS WHICH MOVES THE LOW THE
FARTHEST WEST...BECAUSE OF A LACK OF CONFIDENCE IN THE STEERING FLOW
THAT WOULD RESULT IN THAT WESTWARD JOG. THE FARTHER EAST THE LOW
TRACKS...THE MORE LIKELY THAT THE WESTERN CAROLINAS/NE GEORGIA WILL
REMAIN UNDER SOME SORT OF WEAK SUBSIDENCE...OR AT LEAST AN AREA OF
RELATIVELY DRY AIR...AROUND THE PERIPHERY OF THE LOW. FOR THAT
REASON...AM NOT PARTICULARLY EXCITED ABOUT PRECIP CHANCES THRU THE
PERIOD...AND ESPECIALLY NOT THURSDAY WHEN THE LOW IS STILL WELL
OFFSHORE. THINK THE BEST CHANCE FOR CONVECTIVE PRECIP ON THURSDAY
WILL BE ON THE TN BORDER WHERE WEAK MOISTURE CONVERGENCE WILL BE
BEST. ON FRIDAY...THERE IS THE CHANCE THAT SOME PRECIP COULD DRIFT
IN FROM THE EAST DURING THE DAY...SO THE PRECIP CHANCES RAMP UP
THERE...AND ARE KEPT THRU FRIDAY NIGHT. MEANWHILE...THE USUAL
DIURNAL WEAKENING CAN BE EXPECTED OVER THE MTNS. TEMPS SHOULD BE A
BIT ABOVE NORMAL...WITH SLIGHTLY COOLER HIGHS OVER THE EASTERN-MOST
ZONES WHERE PRECIP/CLOUDS COULD MOVE IN FRIDAY.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 330 AM WEDNESDAY...WE FOCUS ON THE POTENTIAL FOR LOW PRESSURE
OF SOMEWHAT TROPICAL NATURE EITHER OFF THE CAROLINA COAST OR OVER
THE COASTAL PLAIN DEPENDING ON WHICH MODEL SOLUTION ULTIMATELY HAS
THE BEST HANDLE ON IT. ALL THE GUIDANCE SUGGESTS THE LOW WILL MOVE
SLOWLY N BUT BE LEFT ADRIFT FOR THE WEEKEND. THE ECMWF KEEPS THE LOW
OFFSHORE THRU MOST OF THE PERIOD AND THAT SOLUTION WAS GENERALLY
FAVORED WITH THE THINKING THAT THE LOW MIGHT STAY CLOSER TO THE GULF
STREAM WHERE INSTABILITY WILL BE BETTER. THAT WOULD KEEP THE WESTERN
CAROLINAS/NE GEORGIA IN THE UNFAVORABLE AREA WELL W/NW OF THE LOW
WHERE WEAK SUBSIDENCE AND DRY AIR GETTING ENTRAINED FROM THE N WOULD
KEEP A LID ON CONVECTION. WILL NOT MAKE MANY CHANGES TO THE FCST
BECAUSE OF THE CONTINUED UNCERTAINTY...BUT WILL TAKE THIS
OPPORTUNITY TO IMPROVE SOME INCONSISTENCY WITH NEIGHBORING FCST
OFFICES IN TERMS OF PRECIP CHANCES. IT LOOKS LIKE THE LOW WILL
FINALLY DRIFT AWAY TO THE EAST ON MONDAY. THEREAFTER...WE LOOK TO A
SURFACE FRONT COMING IN FROM THE WEST AS THE UPPER PATTERN FINALLY
STARTS MOVING AGAIN.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...QUIET CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD
WITH GENERALLY JUST PATCHY HIGH CLOUDINESS. LIGHT GENERALLY
EASTERLY WINDS SHOULD BACK TO THE NE OVERNIGHT AND CONTINUE ON
THURSDAY AS A SUBTROPICAL LOW MOVES NORTHWARD OFF THE EAST COAST
OF FLORIDA.

ELSEHWERE...GENERALLY VFR WITH LIGHT WINDS. THE EXCEPTION WILL BE
FOR A FEW HOURS EARLY THURSDAY WHERE FOG MAY REDUCE VSBY`S AT KAVL
AND KHKY TO MVFR.

OUTLOOK...GENERALLY VFR OUTSIDE THE MOUNTAINS EXCEPT FOR PATCHY
MORNING FOG. OVER THE MOUNTAINS AS MOIST UPSLOPE FLOW
PERSISTS...ISOLATED TO SCATTERED DIURNAL CONVECTION IS EXPECTED
THROUGH THE WEEKEND WHICH WILL PRODUCE LOCAL RESTRICTIONS. LOW
CLOUDS AND OR FOG RESTRICTIONS WILL BE POSSIBLE EACH MORNING.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...PM
NEAR TERM...LG
SHORT TERM...PM
LONG TERM...PM
AVIATION...LG


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