Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 271747
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
147 PM EDT THU AUG 27 2015

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL MOVE OFF THE MID-ATLANTIC COAST THROUGH
THE END OF THE WEEK...RESULTING IN INCREASING MOISTURE AND CHANCES
FOR SCATTERED SHOWERS AND THUNDERSTORMS OVER THE WEEKEND INTO EARLY
NEXT WEEK. TROPICAL CYCLONE ERIKA IS EXPECTED TO APPROACH THE EAST
COAST OF FLORIDA BY LATE IN THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM EDT THURSDAY...LOWERED POPS SLIGHTLY ATOP THE NC
MTN TOPS WHERE CONFIDENCE IN CONVECTION REMAINS LOW AS LATEST
MESOANALYSIS FAVORS LESS THAN 500J/KG CAPE.  OTHERWISE...TWEAKED
TEMPS/DEWS AND SKY IN THE IMMEDIATE NEAR TERM.  FULL FCST DISCUSSION
TO FOLLOW WITHIN THE HOUR.

AS OF 315 AM...THE UPPER TROF WILL BEGIN TO SPLIT TODAY...WITH
THE SOUTHERN END TRYING TO CLOSE OFF INTO AN UPPER LOW...WHILE THE
NORTHERN PORTION PULLS AWAY ACRS THE NORTHEAST STATES. THIS WILL
PLACE THE CWFA WITHIN THE SHEAR AXIS...AND MAY HELP ERODE SOME OF
THE MID LVL CAPPING INVERSION. ALSO...LLVL FLOW WILL INCREASE OUT
OF THE EAST...AS LOW PRES RETROGRADES FROM THE SC COAST TO SW GA
BY THIS EVENING. THE EASTERLY FLOW WILL CONTINUE TO SUPPLY ATLANTIC
MOISTURE UNDERNEATH THE INVERSION. SO THERE SHUD BE A MIX OF SUN AND
CLOUDS AGAIN TODAY...ESP ACRS THE HIGH TERRAIN. THE USUAL MODELS
INCLUDING MOST OF THE CAMS DEPICT ISOLATED TO SCATTERED MTN-TOP
CONVECTION THIS AFTN. THE NAM HAS 500-1500 J/KG OF SBCAPE...BUT
AGAIN MAY NOT BE ACCOUNTING FOR THE MID LVL INVERSION. SO I THINK
THERE IS A SLIGHTLY BETTER CHC THAT A FEW OF THE CUMULUS WILL
BECOME DEEP ENUF TO PRODUCE A FEW SHOWERS AND PERHAPS AN ISOLATED
GARDEN-VARIETY TSTM. BUT OVERALL...I EXPECT A DRY FCST FOR THE
NEAR TERM. TEMPS SHUD BE SIMILAR TO YESTERDAY/S READINGS...ABOUT
A CATEGORY BELOW NORMAL.

TONIGHT...INCREASING LLVL MOISTURE IN THE FORM OF BOTH HIGHER
DEWPTS AND CLOUD COVER MAY KEEP TEMPS CLOSER TO NORMAL OR EVEN
A CATEGORY ABOVE NORMAL IN SPOTS. BUT I EXPECT ANY SHWRS THAT
DEVELOP WILL DISSIPATE QUICKLY WITH LOSS OF HEATING AFTER SUNSET.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 325 AM THURSDAY...THE SOUTHEAST COASTAL STATES WILL COME
INCREASINGLY UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE/BERMUDA HIGH
DURING THE SHORT TERM...WHICH WILL RESULT IN INCREASING LEVELS OF
MOISTURE AND INSTABILITY OVER OUR AREA. CONDITIONS SHOULD BE
SUFFICIENT TO BREAK THE DRY SPELL AND ALLOW SOME CONVECTION TO FIRE
OVER THE HIGH TERRAIN FRI AFTERNOON...ALTHOUGH COVERAGE IS EXPECTED
TO REMAIN ISOLATED. MEANWHILE...A WEAKNESS IN THE SUBTROPICAL RIDGE
AND WEAK CYCLONE WILL PERSIST ACROSS THE GULF OF MEXICO AND ADJACENT
GMEX COASTAL STATES EARLY IN THE PERIOD. THERE ARE INDICATIONS IN
THE NUMERICAL MODEL GUIDANCE THAT THIS CYCLONE WILL LIFT NORTHEAST
AS AN AREA OF HEIGHT FALLS OVERSPREADS THE NORTHERN CONUS OVER THE
WEEKEND. THE GFS HAS BEEN PARTICULARLY CONSISTENT WITH THIS
SCENARIO...RESULTING IN SUBSTANTIAL INCREASE IN DEEP LAYER MOISTURE
OVER OUR AREA BY THE END OF SATURDAY. THE NAM AND ECMWF ARE
BEGINNING TO LATCH ON TO THIS SCENARIO AS WELL. THAT BEING THE
CASE...30-40 POPS WILL BE CARRIED ACROSS MUCH OF THE FORECAST AREA
FROM SAT AFTERNOON THROUGH SUNDAY...ALTHOUGH THESE COULD PROVE TO BE
TOO CONSERVATIVE. DESPITE INCREASING THICKNESS VALUES...MAX TEMPS
ARE EXPECTED TO REMAIN CLOSE TO CLIMO...OWING TO INCREASING
MOISTURE/CLOUD COVER...WHILE MIN TEMPS SHOULD CREEP ABOVE NORMAL FOR
THE SAME REASON.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 335 AM THURSDAY...THE GLOBAL MODELS ARE IS AGREEMENT IN
BUILDING A MASSIVE UPPER RIDGE ACROSS THE EASTERN CONUS BY THE
MIDDLE OF NEXT WEEK...ALBEIT WITH SOME TYPE OF WEAKNESS/REMNANT WEAK
CYCLONE PERSISTING SOMEWHERE OVER THE EASTERN HALF OF THE CONUS.
SOUTHERLY LOW LEVEL FLOW AND HEAT/HUMIDITY UNDER THE RIDGE SHOULD
ALLOW FOR SUFFICIENT INSTABILITY TO SUPPORT AT LEAST ISOLATED
DIURNAL CONVECTION THROUGH THE PERIOD. OF COURSE...THE ELEPHANT IN
THE ROOM REVOLVES AROUND THE FATE OF TROPICAL CYCLONE ERIKA. IT
SHOULD BE SAID THAT WITH THE EXPECTED EVOLUTION IN THE UPPER PATTERN
(MASSIVE RIDGE OVER THE EAST)...UNCERTAINTY REGARDING THE EVENTUAL
TRACK WILL BE HIGHER THAN NORMAL. THE OFFICIAL NHC TRACK CONTINUES
TO CURVE THE CYCLONE ACROSS THE BAHAMAS TOWARD THE EASTERN FLORIDA
COAST BY DAY 5. THIS IS CERTAINLY IN KEEPING WITH A CONSENSUS OF
NUMERICAL GUIDANCE. HOWEVER...AFTER DAY 5...THERE IS QUITE A BIT OF
DIVERGENCE AMONG THE GLOBAL MODELS...WITH THE ECMWF SPINNING DOWN
THE CYCLONE OVER THE DEEP SOUTH...WHILE THE GFS KEEPS THE STORM OFF
THE COAST AND STRENGTHENS IT AS IT ENCOUNTERS THE GULF STREAM BEFORE
MAKING LANDFALL ON THE SC COAST BY DAY 7. AGAIN...CONFIDENCE IN ANY
SPECIFIC MODEL SOLUTION IS EXTREMELY LOW AT THIS POINT OWING TO THE
NEBULOUS UPPER PATTERN. STAY TUNED...

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...VFR THROUGH THE PERIOD HOWEVER WITH THE POSSIBILITY OF
MVFR CIGS BY EARLY/MID MORNING FRIDAY.  INITIALIZED TAF WITH LIGHT
NE GUSTS AND SCT LOW VFR AS LATEST VISIBLE SAT INDICATES MODEST CU
IN THE REGION.  MODELS HAVE TRENDED TOWARDS A SHALLOWER...LESS
MOIST LAYER BY DAYBREAK FRIDAY WHICH COULD INHIBIT ANY MVFR
CIG DEVELOPMENT.  NEVERTHELESS...IT REMAINS POSSIBLE THAT CIG
RESTRICTIONS COULD OCCUR AND THEREFORE OPTED TO CONTINUE WITH SCT
MVFR MENTION.  OTHERWISE...ENE WINDS WILL PREVAIL ON FRIDAY WITH
SOME SCATTERING OF LOW CLOUDS EXPECTED TOWARDS EARLY AFTERNOON.

ELSEWHERE...SIMILAR TO THAT OF KCLT ABOVE AS ALL SITES
FEATURE PREVAILING LOW VFR CU CIGS THROUGH THE AFTERNOON AS
LOW LEVEL MOISTURE REMAINS IN PLACE SUPPORTIVE OF SUCH AMONGST
LIGHT/MODERATE NE FLOW.  REGARDING ANY RESTRICTIONS OVERNIGHT
DUE TO MOISTURE ADVECTING IN FROM THE EAST...PER PREVIOUS/LATEST
GUID KEPT ANY MVFR/IFR FROM TAFS AND THUS OPTED TO CONTINUE SCT
MVFR MENTION...ASIDE FOR AT KAVL WHERE GUIDANCE HAD A FAIRLY
GOOD CONSENSUS ON MOUNTAIN VALLEY FOG/STRATUS THUS RESTRICTIONS
WERE INCLUDED.  CONDITIONS WILL IMPROVE AT ALL SITES THROUGH FRIDAY
MORNING WITH LOW VFR CU PREVAILING LATE IN THE PERIOD ATOP CONTINUED
ENE FLOW.

OUTLOOK...MOISTURE WILL SLOWLY INCREASE FROM THE SOUTH AND EAST
THROUGH THE WEEKEND AND THEREFORE ISOLATED TO SCATTERED AFTERNOON
AND EVENING SHRA/TSRA CHANCES WILL INCREASE.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     LOW   57%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     LOW   57%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     LOW   59%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     LOW   40%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     MED   64%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     LOW   48%

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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JDL
NEAR TERM...ARK/CDG
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...CDG


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