Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 070226
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1026 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/...
1015 PM UPDATE...ALL CONVECTION HAS MOVED OFF THE SPINE OF THE
APPS...THE MEAN EASTERLY FLOW HAVING PUSHED IT INTO EAST TN.
ACTIVITY OVER VA IS DYING AS INSTABILITY IS USED UP. HAVE REMOVED
ALL POPS FROM THE FCST TONIGHT. CIRRUS CONTINUE TO STREAM NWD ACRS
THE ERN HALF OF THE CWFA AND THIS LOOKS TO CONTINUE...SO THIS AREA
HAS BEEN UPPED TO MOSTLY CLOUDY WORDING FOR THE NIGHT. TEMPS HAVE
COOLED FASTER THAN THE AVBL HRLY GUIDANCE...BUT TRIED TO MAKE
APPROPRIATE ADJUSTMENTS BASED ON THE LATEST OBS AND TRENDS FROM THE
LAMP AND RAP. STILL THINKING FOG IS UNLIKELY EVEN IF DEWPTS ARE
REACHED.

AS OF 730 PM...HIGH PRESSURE CONTINUES TO RIDGE SOUTHWEST FROM THE
MID-ATLANTIC REGION INTO THE SOUTHERN APPALACHIANS. HOWEVER...THE
SUBTROPICAL LOW OFF THE EAST COAST OF FLORIDA WILL DRIFT NORTHWARD
TONIGHT WITH THE BIGGEST AFFECT FOR OUR AREA BEING PATCHY HIGH
CLOUDINESS. LOW TEMPS TONIGHT WILL REMAIN MILD WITH LOWS FROM 55 TO
60 OUTSIDE THE MOUNTAINS AND 50-55 MOUNTAIN VALLEYS. LOW LEVEL
PROFILES REMAIN PRETTY DRY...AND DEWPOINTS MIXED OUT ENOUGH THIS
AFTERNOON THAT FOG LOOKS UNLIKELY FOLLOWING UPS TECHNIQUE. REMOVED
FOG MENTION FROM FCST.

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 /03Z THURSDAY THROUGH MONDAY/...
AT KCLT...VFR. DRY LLVL PROFILES AND SFC DEWPOINTS WILL BE
UNSUPPORTIVE OF RESTRICTIONS THU MRNG. WINDS ARE MOST LIKELY TO HOLD
ESE THROUGH THE EVENING BEFORE BACKING TO NWLY...AHEAD OF
SUBTROPICAL LOW PRESSURE SYSTEM MOVING TOWARD THE NC COAST. THE NELY
WINDS WILL CONTINUE THRU THE DAY THU. AS THE SYSTEM NEARS AND THE
GRADIENT AMPLIFIES IN THE AFTN...CONCURRENT WITH FAIRLY DEEP
MIXING...WINDS ARE EXPECTED TO BECOME GUSTY. INCREASING/THICKENING
CIRRUS WILL BE SEEN AS THE DAY PROGRESSES.

ELSEWHERE...VFR EXPECTED THIS PERIOD WITH CONDITIONS REMAINING DRY
ENOUGH TO PRECLUDE MRNG RESTRICTIONS. WINDS WILL BE MAINLY CALM
OVERNIGHT BUT SHOULD COME UP FROM THE N OR NE THU MRNG. KAVL WILL
FLIP TO SELY LATER IN THE DAY. A FEW LOW END GUSTS ARE LIKELY...BUT
APPEAR INFREQUENT ENOUGH TO OMIT FROM THE TAFS. FEW-SCT SHRA/TSRA
ARE EXPCD OVER THE MTNS...BUT CHC AT KAVL IS TOO LOW TO MENTION.

OUTLOOK...MOIST UPSLOPE FLOW PERSISTS INTO THE AREA...SO ISOLATED TO
SCATTERED DIURNAL CONVECTION IS EXPECTED THROUGH THE
WEEKEND...PRODUCING WILL PRODUCE LOCAL RESTRICTIONS. LOW CLOUDS AND
OR FOG RESTRICTIONS WILL BE POSSIBLE EACH MORNING.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
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...JPT
NEAR TERM...LG/WIMBERLEY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...WIMBERLEY


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.