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 272011
AFDGSP

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

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

&&

.NEAR TERM /THROUGH FRIDAY/...
2015 UTC UPDATE...SKY COVER WAS UPDATED PER THE LATEST VISIBLE
SATELLITE IMAGERY...RESULTING IN A SLIGHT DECREASE ACROSS MUCH OF
THE AREA.

AS OF 230 PM EDT THURSDAY...NEARLY FULL LATITUDE DECOUPLING
UPPER TROF RESIDES OVER THE EASTERN CONUS WHILE ANTICYCLONIC
FLOW PREVAILS AROUND AN UPPER HIGH OVER THE DESERT SOUTHWEST.
AT THE SURFACE...A NEARLY STATIONARY COLD FRONTAL AXIS OFF THE
CAROLINA COASTLINE CONTINUES TO PROVIDE A FOCUS FOR CONVECTION OVER
THAT REGION.  CLOSER TO HOME...LATEST SPC MESOANALYSIS INDICATES
MINOR DESTABILIZATION ACROSS PORTIONS OF WESTERN NC AND ALL OF
NORTHEAST GA AND THE SC UPSTATE...WHICH CONTINUES TO PROMOTE LOW
CU DEVELOPMENT.  AS THE UPPER PATTERN DECOUPLES...ANY NORTHERN
STREAM SHORTWAVE ENERGY WILL SLIDE ACROSS THE SOUTHERN/CENTRAL
APPS LATER THIS AFTERNOON INTO EARLY EVENING.  MODELS CONTINUE TO
INDICATE SOME CONVECTION ALONG THE MTN RIDGETOPS...POSSIBLY AIDED
BY VEERED EASTERLY UPSLOPING...THEREFORE CONTINUED WITH LOW END
SLIGHT CHANCE POPS INTO EARLY EVENING BEFORE ALL POPS ARE REMOVED
CLOSER TO MIDNIGHT.

SURFACE HIGH PRESSURE WILL ADVECT ACROSS THE APPS THROUGH THE
OVERNIGHT WHILE THE SOUTHERN STREAM UPPER WAVE RETROGRADES SLIGHTLY
TO THE WEST OVER THE NORTHCENTRAL GULF.  MODELS INDICATE EASTERLY
VEERED SFC-H85 FLOW THROUGH FRIDAY MORNING LEADING TO WEAK UPGLIDE
POTENTIAL ATOP THE INTRUDING SUMMERTIME WEDGE LIKE SFC PRESSURE
PATTERN THANKS TO HIGH PRESSURE OFF TO THE IMMEDIATE NORTHEAST.
AS A RESULT...PARTLY/MOSTLY CLOUDY SKIES ARE EXPECTED FRIDAY
MORNING...ESPECIALLY ACROSS THE EASTERN TIER OF THE FCST AREA.
SAID SKY COVER WILL EVENTUALLY SCT INTO THE LATE MORNING TO EARLY
AFTERNOON AS THE BOUNDARY LAYER HEATS YIELDING A FEW CUMULUS THROUGH
THE PERIOD.  AS FOR PRECIPITATION...MODELS ARE FAIRLY CONSERVATIVE
WITH REGARDS TO DESTABILIZATION WITH THE BEST OF WHICH RESIDING
ONCE AGAIN ALONG THE HIGH TERRAIN WHERE DIFFERENTIAL HEATING WILL
BE MAXIMIZED...THUS THE FCST FEATURES SLIGHT CHANCE POPS FOR SUCH.
TEMPERATURES ON FRIDAY WILL REMAIN A FEW DEGREES BELOW NORMAL.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM THURSDAY...SHORT TERM BEGINS WITH LONGWAVE UPPER TROUGH
LIFTING INTO CANADA...WITH UPPER WEAKNESS/ENERGY OVER THE SOUTHEAST
AND LOWER MISSISSIPPI VALLEY BREAKING OFF. A WEAK SURFACE LOW
DEVELOPING OFF THE CAROLINA COAST WILL BEGIN TO LIFT NORTHEAST...AND
WITH SURFACE HIGH IN PLACE OVER THE MID-ATLANTIC STATES THE
SOUTHEASTERLY FLOW WILL BEGIN TO BRING MORE MOISTURE INTO THE REGION
FOR THE SHORT TERM. THE UPPER WEAKNESS OVER THE SOUTHEAST WILL BEGIN
TO PHASE WITH ANOTHER SHORTWAVE CROSSING THE GREAT LAKES SATURDAY
INTO SUNDAY...THE LATTER HELPING TO PULL THE FORMER BACK TO THE
NORTHEAST. AS IT DOES SO...AN ASSOCIATED VORT MAX AND EVEN A WEAK
UPPER JET WILL PUSH ACROSS THE CAROLINAS. AS A RESULT...EXPECT
CLOUDS TO BE ON THE INCREASE ESPECIALLY ON SATURDAY...AS POPS SPREAD
ACROSS THE AREA FROM THE SOUTH AND SOUTHWEST AS WELL...WITH SOME
LIKELIES SHOWING UP ACROSS THE MOUNTAINS AND FOOTHILLS BY SUNDAY
AFTERNOON. WITH INCREASED CLOUDS AND CHANCE OF PRECIPITATION...
EXPECT HIGHS TO CONTINUE TO HOVER JUST BELOW SEASONAL NORMALS BUT
WITH LOWS INCREASING TO ABOVE NORMAL VALUES AS A RESULT OF THE
ADDITIONAL SURFACE MOISTURE. DEFINITELY SOME DIFFERENCES IN
AVAILABLE INSTABILITY BETWEEN THE GFS AND NAM BUT INSTABILITY WILL
INCREASE FROM THE SOUTHWEST SATURDAY...WITH THUNDER POSSIBLE PRETTY
MUCH ACROSS THE ENTIRE AREA ON SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 245 PM THURSDAY...MEDIUM RANGE/EXTENDED HAS A LOT OF
UNCERTAINTY ESPECIALLY THE FARTHER OUT WE GO IN THE FORECAST. TO
START WITH...THE UPPER WEAKNESS FROM THE SHORT TERM WILL SLOWLY
DISSIPATE AS IT PHASES WITH AND IS ABSORBED BY THE LONGWAVE TROUGH
WITH THE WAVETRAIN UP ALONG THE U.S./CANADA BORDER. THIS GIVES WAY
TO UPPER RIDGING BY TUESDAY. THE PATTERN SUPPORTS A SLIGHT
INCREASING TREND IN TEMPERATURES...BUT THE UNKNOWNS START PILING UP
QUICKLY DEPENDING ON WHAT ERIKA DECIDES TO DO. CURRENT OFFICIAL
FORECAST HAS THE STORM HUGGING THE EAST SIDE OF THE FLORIDA
PENINSULA AS A HURRICANE THROUGH TUESDAY MORNING. 12Z GUIDANCE /BOTH
GFS AND ECMWF/ KEEP IT RIGHT ALONG THE SOUTH CAROLINA COAST...AND
THEN PUSH IT EAST AND OUT TO SEA AS THE UPPER RIDGE PUSHES EAST.
THIS COULD VERY LIKELY LEAVE OUR AREA MOSTLY DRY. FOR NOW THOUGH
HAVE TAKEN A SPLIT POP PARADIGM WITH CHANCE POPS IN SOUTHEAST
ZONES...IN CLOSER PROXIMITY TO THE INFLUENCE OF ERIKA...AND CHANCE
POPS IN THE MOUNTAINS...AS NORTHWEST FLOW INCREASES AND WOULD LEND
THE UPSLOPE COMPONENT TO THE AREA DESPITE SYNOPTIC SUBSIDENCE AROUND
THE PERIPHERY OF THE STORM...WITH SLIGHT CHANCE BETWEEN. WITHOUT
DIFFERENT GUIDANCE...HAVE KEPT TREND OF HIGHS AT OR JUST SLIGHTLY
BELOW SEASONAL NORMALS AND LOWS AT OR JUST SLIGHTLY ABOVE. OBVIOUSLY
HIGHLY DEPENDENT ON BOUNDARY LAYER MOISTURE. HOWEVER...OF COURSE ANY
SHIFT IN THE TRACK WILL HAVE VARYING IMPACTS ON THE FORECAST FOR
NEXT WEEK SO STAY TUNED.

&&

.AVIATION /20Z 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...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     MED   78%     MED   70%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  90%     MED   68%     HIGH  93%
KHKY       HIGH 100%     HIGH 100%     HIGH  83%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  95%     HIGH  97%

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...JPT
NEAR TERM...CDG/JAT
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...CDG


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