Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 171808
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
208 PM EDT WED SEP 17 2014

.SYNOPSIS...
A COOL RIDGE OF HIGH PRESSURE WILL SLOWLY BUILD SOUTHWEST ACROSS THE
AREA THROUGH TONIGHT...THEN INTENSIFY ON FRIDAY. THIS PATTERN IS
EXPECTED TO PERSIST THROUGH THE WEEKEND...BEFORE A COLD FRONT
CROSSES THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 200 PM EDT...VISIBLE SATELLITE IMAGERY THIS AFTERNOON IS
FINALLY SHOWING FASTER EROSION OF THE LOW CLOUD LAYER IN THE WEAK
CAD REGION N OF THE RECENTLY DEPARTED BACKDOOR FRONT. THIS SHOULD
CONTINUE AS VAD WIND PROFILES INDICATE LITTLE RESIDUAL UPGLIDE OVER
THE CAD. HOWEVER...BOUNDARY LAYER MOISTURE IS ALLOWING SOME CUMULUS
REDEVELOPMENT AS SCATTERING OCCURS...AND WEAK PASSING H5 SHORTWAVES
ALOFT COULD TRIGGER SOME ISOLD SHALLOW CONVECTION ALONG THE MOST
UNSTABLE SRN/ERN MTNS AND SE PIEDMONT THROUGH EARLY EVENING. THE
BEST FOCUS OF ANY UPPER FORCING SHOULD BE WITH A 60 TO 70 KT UPPER
JETLET CROSSING THE REGION IN WNW FLOW ALOFT...PLACING THE BEST
UPPER DIVERGENCE OVER THE MIDLANDS AND PIEDMONT EAST OF OUR FORECAST
AREA TOWARD EVENING. OTHERWISE...ANTICIPATE MOSTLY DRY CONDITIONS
WITH LOW CLOUDS AND PATCHY FOG FILLING BACK IN ACROSS THE REGION
OVERNIGHT AS SFC WINDS SLACKEN.

A TRAIN OF ADDITIONAL WEAK SHORTWAVES WILL CONTINUE TO PUSH INTO THE
ERN TROUGH ON THU...BUT AGAIN WITH WEAK TRIGGERING AND LIMITED
MOISTURE. WILL FEATURE LOW END ISOLD POPS FOR THU AFTN AS 850 TO 500
MB LAPSE RATES REMAIN REASONABLY STEEP AT 6.5 DEG C/KM. LOW CLOUDS
SHOULD SCATTER A BIT MORE QUICKLY THU...RESULTING IN MAX TEMPS A
DEGREE OR TWO WARMER IN MOST AREAS...BUT STILL A LITTLE BELOW CLIMO.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
AS OF 300 AM WED...CANADIAN HIGH PRESSURE WILL SPREAD EWD INTO THE
NERN STATES THU AND THU NIGHT...EXTENDING SOUTHWARD ENOUGH TO
REINFORCE THE ALREADY COOL AIR IN PLACE OVER THE CWFA. WITH UPPER
TROUGH AXIS ALREADY EAST OF THE AREA...SUBSIDENCE IS IMPLIED AND PROG
SOUNDINGS FROM NAM/GFS INDICATE CAPPING ALOFT THOUGH THE GFS LAPSE
RATES ARE FAVORABLE ENOUGH TO THINK A FEW TOWERING CU COULD GO UP. AN
EMBEDDED SHORTWAVE WILL DRIFT OVER THE AREA EARLY IN THE DAY ALBEIT
WITHOUT MUCH MOISTURE TO WORK WITH. WILL INCLUDE A SCHC POP AHEAD OF
THE WAVE BUT EXPECT AFTN CONVECTION TO BE INHIBITED.

A CAD EVENT WILL TAKE SHAPE BY THE END OF THE DAY THU AS THE SFC HIGH
SHIFTS ACRS THE MTNS. FRIDAY THE UPPER FLOW WEAKENS OVER THE
AREA...WITH BOTH NAM/GFS BASICALLY SHOWING THE TROUGH FILLING OVER
THE SOUTHEAST. THE PARENT HIGH STAYS IN MOTION AS A RESULT...MOVING
OFFSHORE BUT MAINTAINING RIDGING DOWN THE ERN SEABOARD. THE
SUBSIDENCE ALOFT BEING WEAKER...CAPPING IS LESS CERTAIN DURING
HEATING FRIDAY AFTN. ALLOWED A SCHC POP TO RETURN TO THE FCST IN THE
MOST FAVORED AREA...ALONG THE BLUE RIDGE WHERE EASTERLY UPSLOPE FLOW
WILL ENHANCE DEVELOPMENT.  US MODELS BEAR THEIR USUAL DISCREPANCIES
IN TERMS OF CAPE...BUT AGREE THAT SHEAR WILL BE VERY WEAK AND
PROFILES QUITE DRY THROUGH A DEEP LAYER. WE/D PROBABLY BE DEALING
WITH PULSE STORMS POSING A DAMAGING WIND THREAT IF CELLS WERE TO
DEVELOP.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 615 AM WED...NO WHOLESALE CHANGES TO THE EXPECTATIONS FOR THE
WEEKEND AND EARLY NEXT WEEK. ON SATURDAY THE PARENT HIGH ASSOCIATED
WITH THE LATE-WEEK COLD AIR DAMMING WILL BE FORCED FURTHER OFFSHORE.
EASTERLY FLOW MAY CONTINUE IN THE LOW LEVELS...BUT THE INFLUENCE OF
THE WEDGE WILL BE MINIMAL. THE PATTERN SHIFTS AND RETURN FLOW BEGINS
SUNDAY AHEAD OF THE NEXT SYSTEM AFFECTING THE ERN CONUS. A WEAK AREA
OF LOW PRESSURE OFF THE SOUTHEAST COAST IS SHOWN ON BOTH GFS/EC BUT
DOES NOT APPEAR TO HAVE AN IMPACT THIS FAR INLAND. POPS WILL REMAIN
UNMENTIONABLY LOW. TROUGH DIGS INTO THE OHIO VALLEY AND MID-ATLANTIC
SUNDAY NIGHT...ACCOMPANIED BY A COLD FRONT. GFS CONTINUES TO BE A
LITTLE FASTER THAN THE EC IN BRINGING THE FRONT INTO THE AREA...AND
THE EC DEPICTION OF THE TROUGH CONTINUES TO BE STRONGER. POPS MONDAY
APPEAR TO BE A BIT HIGHER THAN CLIMO THOUGH NEITHER MODEL DEVELOPS
SIGNIFICANT QPF AT THIS TIME. BOTH GFS/EC DO SHOW SOME INSTABILITY
AHEAD OF THE FROPA. TEMPS INCREASE SLIGHTLY EACH DAY THRU
MONDAY...WITH MAXES AROUND CLIMO THAT DAY. THEY THEN DROP A COUPLE
CATEGORIES FOR TUESDAY.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...VISIBLE IMAGERY SHOWS SLIGHT SCATTERING AND IMPROVEMENT OF
THE LOW CEILINGS ARRIVING FROM THE EAST AT ISSUANCE TIME. ANTICIPATE
FAIRLY SOLID MVFR RESTRICTIONS THROUGH THE LATE AFTN HOURS...WITH
ANY RECOVERY TO VFR LIKELY VERY BRIEF THIS EVENING BEFORE MVFR CIGS
RETURN QUICKLY IN THE ABUNDANT BOUNDARY LAYER MOISTURE OVERNIGHT.
THERE IS DEVELOPING CONSENSUS THAT A ROUND OF VLIFR TO LIFR
RESTRICTIONS MAY RETURN BY 09Z. WILL TREND THE TAF TOWARD LOWER END
IFR FOR NOW. RECOVERY THROUGH MVFR WILL TAKE THE BETTER PART OF THU
MORNING. ALTHOUGH WEAK SHORTWAVES WILL MOVE OVERHEAD...TIMING IS TOO
UNCERTAIN TO FEATURE ANY PRECIPITATION IN THE TAF AT PRESENT. EXPECT
LIGHT NE SFC WINDS THROUGHOUT.

ELSEWHERE...SLOW BUT STEADY IMPROVEMENTS IN MVFR CIGS ARE EXPECTED
AT THE MTN AND FOOTHILL TAF SITES THROUGH LATE AFTERNOON. A BRIEF
PERIOD OF VFR IS EXPECTED...BUT THIS SHOULD BE FAIRLY SHORT LIVED AS
CIGS RETURN QUICKLY TO MVFR OVERNIGHT GIVEN THE ABUNDANT BOUNDARY
LAYER MOISTURE. ISOLD SHRA CANNOT BE RULED OUT AT KAVL AND THE
UPSTATE TAFS THIS EVENING WITH PASSING SHORTWAVES OVERHEAD...BUT THE
FORCING IS TOO WEAK AND UNCERTAIN TO TIME. EXPECT A PERIOD OF IFR TO
LIFR RESTRICTIONS TO DEVELOP THROUGH DAYBREAK AS THE SFC WINDS
SLACKEN IN THE WEAK CAD REGIME. SLOW BUT STEADY LIFTING FROM IFR
THROUGH MVFR IS EXPECTED THU MORNING. SFC WINDS WILL CONTINUE
NE...EXCEPT TURNING FROM SE TO NW AT KAVL THROUGH THE PERIOD.

OUTLOOK...THE POTENTIAL FOR LATE NIGHT/MORNING FOG/STRATUS WILL
PERSIST INTO THE EARLY PART OF THE WEEKEND...ESPECIALLY IN THE MTN
VALLEYS. CONDITIONS MAY FINALLY DRY OUT FOR THE LATTER PART OF THE
WEEKEND. A COLD FRONT MAY BRING INCREASING CHANCES FOR SHOWERS/TSTMS
EARLY NEXT WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  85%     MED   79%     MED   72%     MED   76%
KGSP       HIGH  84%     HIGH 100%     MED   69%     MED   68%
KAVL       HIGH  85%     HIGH  96%     MED   77%     HIGH  82%
KHKY       HIGH  83%     HIGH 100%     MED   70%     MED   66%
KGMU       HIGH  81%     HIGH 100%     MED   69%     MED   70%
KAND       MED   77%     HIGH 100%     MED   72%     MED   79%

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...DEO
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...HG





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