Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 062045
AFDGSP

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

.SYNOPSIS...
WEAK HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH THURSDAY...
AS LOW PRESSURE ORGANIZES EAST OF FLORIDA. THE LOW MAY DEVELOP
INTO A TROPICAL OR SUBTROPICAL FEATURE BY THIS WEEKEND...AS IT
DRIFTS NORTH TOWARD THE SOUTH CAROLINA COAST. THERE IS STILL PLENTY
OF UNCERTAINTY AS TO WHETHER OR NOT THE SYSTEM REMAINS OFFSHORE OR
MOVES INLAND OVER THE COASTAL PLAIN OF THE CAROLINAS THIS WEEKEND.
THE LOW WILL EVENTUALLY DRIFT EAST OF THE AREA...AS A COLD FRONT
PUSHES IN FROM THE WEST ON TUESDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
430 PM UPDATE...THE FCST IS ON TRACK. MADE SLIGHT TWEAKS TO
POP/SKY PER SATELLITE AND RADAR OBS...AND LATEST AVBL HRRR WHICH HAS
BACKED OFF ITS EXPECTATIONS FOR CONVECTION NEAR THE BLUE RIDGE.
CONVECTION SHOULD CONTINUE TO BUBBLE NEAR THE TENN BORDER THRU
SUNSET.

AS OF 200 PM...NO BIG CHANGE IS ANTICIPATED FOR THE OVERNIGHT AS
HIGH PRESSURE CONTINUES TO RIDGE SOUTHWEST FROM THE MID-ATALNTIC
REGION INTO THE SOUTHERN APPALACHIANS. HOWEVER...THE SUBTROPICAL LOW
OFF THE EAST COAST OF FLORIDA WILL DRIFT NORTHWARD WITH THE BIGGEST
AFFECT FOR OUR AREA PATCHY HIGH CLOUDINESS. LOW TEMPS TONIGHT WILL
REMAIN MILD WITH LOWS FROM 55 TO 60 OUTSIDE THE MOUNTAINS AND 50-55
MOUNTAIN VALLEYS. SOME FOG IS LIKELY TO DEVELOP AGAIN IN THE
MOUNTAIN VALLEYS...ESPECIALLY IN THE LITTLE TN VALLEY WHERE FOG IS
LIKELY TO DEVELOP SHORTLY AFTER MIDNIGHT AND PERSIST THROUGH SUNRISE.

ON THURSDAY...THE SUBTROPICAL LOW IS FORECAST TO CONTINUE TO DRIFT
NORTHWARD TO OFF THE SOUTH CAROLINA COAST BY LATE IN THE DAY. MODELS
INDICATE THAT THE NON-MOUNTAIN AREAS SHOULD REMAIN DRY AS THEY WILL
BE IN AN AREA OF GENERAL SUBSIDENCE ALONG WITH DRIER AIR ADVECTING
IN FROM THE NE. HOWEVER...THE MOUNTAINS SHOULD SEE SOME SCT
AFTERNOON CONVECTION THANKS TO LOW LEVEL UPSLOPE FLOW AND A SPOKE OF
VORTICITY ROTATING AROUND THE UPPER LOW INTO THE AREA ALONG WITH
CAPES INCREASING TO 500-1000J/KG. HENCE...WILL CONTINUE TO CARRY SCT
POPS IN THE MOUNTAINS. TEMPS WILL BE A COUPLE DEGREES LOWER THAN
TODAY DUE TO INCREASED CLOUD COVER...BUT STILL ABOVE CLIMO.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 130 PM WEDNESDAY...THE MAIN FCST CHALLENGE FOR THE SHORT TERM
WILL BE HOW MUCH IMPACT THE TROPICAL (OR SUBTROPICAL LOW) WILL HAVE
ON OUR WX ACRS THE WESTERN CAROLINAS AS IT APPROACHES THE SC COAST.
THE MODELS ARE IN A LITTLE BETTER AGREEMENT ON THEIR DEPICTION OF
THE FEATURE...GRADUALLY ORGANIZING IT INTO A CLOSED SFC LOW BY
THURSDAY EVENING...WITH OUTER BANDS OF CONVECTION EXPECTED TO START
AFFECTING THE NC/SC COASTS. IT LOOKS LIKE THE MOST LIKELY SCENARIO
IS FOR THE LOW TO MEANDER NEAR THE SC COAST FRIDAY AND
SATURDAY...KEEPING OUR AREA IN THE SUBSIDENCE BAND ON THE NW SIDE OF
THE CIRCULATION. GUIDANCE DOES ALLOW FOR SOME INSTBY AND MTN-TOP
CONVECTION BOTH DAYS...WITH THE I-77 CORRIDOR POSSIBLY BEING
AFFECTED BY SOME RAIN BANDS. THE BLUE RIDGE...UPSTATE AND NE GA LOOK
TO BE IN THE MINIMUM OF POP BOTH DAYS. TEMPS WILL BE 2-3 CATEGORIES
ABOVE NORMAL THURSDAY NIGHT THRU SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM WEDNESDAY...THE MEDIUM RANGE STARTS AT 00Z
SUNDAY...WITH THE TROPICAL OR SUBTROPICAL LOW SOMEWHERE INVOF THE
SC/NC COAST. THE MODELS STILL DIVERGE ON WHERE THE LOW IS STEERED.
THE LATEST WPC PREFERENCE IS CLOSE TO THE 00Z ECMWF...WHICH HAS THE
LOW DRIFT NORTH INTO ERN NC ON SUNDAY...THEN TURN SLIGHTLY NE OFF
THE VA CAPES. THE GFS IS A SLOW AND WESTERN OUTLIER...HAVING THE LOW
DRIFT SW ON SUNDAY TOWARD SAVANNAH...THEN NE ALONG THE COASTAL PLAIN
ON MONDAY. IF THE GFS VERIFIES...WE WOULD PROBABLY SEE MORE ENHANCED
AFTN/EVE CONVECTION. HOWEVER...GIVEN THE CONSENSUS/WPC TRACK...THE
WESTERN CAROLINAS WILL LIKELY STAY ON THE SUBSIDENCE/BACK SIDE OF
THE SYSTEM...WITH MAINLY JUST SOME MTN CONVECTION AND ISOLD PIEDMONT
ACTIVITY SUNDAY AND MONDAY. I WILL UNDERCUT THE SUPERBLEND POPS BOTH
DAYS ABOUT 10-20 PCT...KEEPING CHC POP IN NC...AND SLGT CHC POP
SOUTH. TEMPS WILL CONTINUE TO BE ABOVE NORMAL...ABOUT 7-10 DEG.

TUESDAY AND WEDNESDAY...THE PERSISTENT WESTERN CONUS TROF WILL EJECT
INTO THE PLAINS...AND LIFT NORTH INTO THE GREAT LAKES. THE FLOW WILL
FLATTEN THE SOUTHEASTERN CONUS RIDGE...BUT NOT COMPLETELY.
STILL...BOTH THE GFS AND ECMWF SHOW A COLD FRONT ASSOCIATED WITH THE
UPPER WAVE PUSHING THRU THE AREA ON TUESDAY. THE GFS HAS IT THRU BY
EARLY MORNING...WHILE THE ECMWF PUSHES IT ACRS TUESDAY EVENING.
AGAIN...THE WPC PREFERENCE IS MORE IN LINE WITH THE EC...SO WILL
CONTINUE THE CHC POPS FOR SHWRS AND TSTMS...WITH ABOVE NORMAL TEMPS
TUESDAY. THEN DRY WEDNESDAY WITH SLIGHTLY COOLER TEMPS.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...IT WILL BE SOMEWHAT DIFFICULT TO NAIL DOWN WINDS THIS
AFTN/EVENING UNDER VERY WEAK FORCING. OVERALL PATTERN SUGGESTS ESE
WINDS WILL BACK TO NE TONIGHT AS A SUBTROPICAL LOW MOVES NORTHWARD
OFF THE EAST COAST OF FLORIDA. NE WINDS WILL CONTINUE TOMORROW.
QUIET CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD WITH GENERALLY
JUST PATCHY CIRRUS...JOINED BY A FEW RATHER HIGH BASED CU FOR THE
REMAINDER OF THE AFTN.

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...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  91%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  83%     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...JPT
NEAR TERM...LG/WIMBERLEY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...LG/WIMBERLEY


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