Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010225
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1025 PM EDT MON AUG 31 2015

.SYNOPSIS...
HIGH PRESSURE WILL LINGER ACROSS THE REGION EARLY THIS WEEK. WEAK
DISTURBANCES MAY RIPPLE ACROSS THE LOWER AND MIDDLE APPALACHIAN
REGION BY MID TO LATE WEEK. A COOL AND MOIST AREA OF HIGH PRESSURE
IS EXPECTED TO SETTLE ACROSS THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA THIS WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 1025 PM...SHRA HAVE DISSIPATED BUT STRATOCU LINGER AND ARE
EVEN EXPANDING. THIS IS LIKELY THE MOISTURE TRAPPED UNDER THE MID
LEVEL SUBSIDENCE INVERSION MENTIONED EARLIER. GOOD NEWS IS THE
CLOUDS ARE VFR. BAD NEWS IS THIS COULD PLAY HAVOC WITH TEMP FCST AND
FOG POTENTIAL OVERNIGHT. FOR NOW...STILL HAVE THE CLOUDS SLOWLY
DISSIPATING WITH MTN VALLEY FOG DEVELOPING AND ONLY A CHANGE IN TEMP
DIURNAL CURVE...NOT THE RESULTANT LOW TEMP.

AS OF 730 PM...LINGERING SHRA ACROSS THE NC MTNS WILL DISSIPATE THIS
EVENING. THE LINGERING CU OUTSIDE OF THE MTNS WILL DISSIPATE QUICKLY
THIS EVENING...BUT DISSIPATE MORE SLOWLY ACROSS THE MTNS. DESPITE
MOISTURE TRAPPED UNDER A MID LEVEL SUBSIDENCE INVERSION...GUIDANCE
SHOWS LITTLE CHC OF LOW CLOUDS OVERNIGHT AS THE LOW LEVEL FLOW WILL
BE W TO NW. HAVE BACKED OFF ON CLOUDS IN RESPONSE. FCST SOUNDINGS
STILL SHOW FOG LIKELY IN THE MTN VALLEYS BECOMING PATCHY DENSE
TOWARD MORNING. FCST LOWS LOOK ON TRACK.

AS OF 425 PM...RADAR SHOWING RIDGE TOP SHRA TRYING TO DEVELOP. BEST
CU FIELDS ARE ALSO THERE. CURRENT FCST TREND OF WITH ISOLATED POP
LIMITED TO THOSE AREAS STILL LOOKS GOOD...BUT CHC OF ANYTHING
SIGNIFICANT IS DIMINISHING. OTHERWISE...FCST ON TRACK WITH UPDATES
MAINLY FOR CURRENT CONDITIONS.

AS OF 230 PM...AN UPPER RIDGE WILL BUILD ALONG THE EAST COAST THRU
THE NEAR TERM. AT THE SFC...A RATHER NEBULOUS PRES PATTERN EXISTS
ACRS MUCH OF THE EASTERN CONUS...WITH A WEAK CENTER OF HIGH PRES
ROUGHLY ACRS THE CENTRAL APPALACHIANS OR JUST TO THE WEST. THIS SET
UP HAS TRAPPED SOME LLVL MOISTURE UNDER A STRENGTHENING MID LVL
INVERSION. THE FLOW IS SO WEAK HOWEVER...THAT THERE IS NO TRIGGER
FOR CONVECTION OR WIDESPREAD CLOUDS OTHER THAN TERRAIN EFFECTS.
THERE IS STILL A SLGT CHC OF MAINLY SHWRS ACRS THE NC MTNS...BUT THE
REST OF THE AREA SHUD BE DRY THRU TONIGHT. TEMPS WILL BE ABOUT A
CATEGORY ABOVE NORMAL...WITH PATCHY FOG AND STRATUS
EXPECTED...MAINLY IN THE MTNS.

TUESDAY...WITH THE CONTINUED UPPER RIDGING...EXPECT THE MID LVLS TO
REMAIN WARM...AND PUT A LID OF MOST DEEP CONVECTION. TEMPS LOOK TO
REBOUND TO A COUPLE CATEGORIES ABOVE NORMAL...WHILE DEWPTS WILL BE
SIMILAR TO MONDAY...IF NOT A DEG OR TWO HIGHER. SO THERE SHUD BE A
LITTLE BETTER INSTBY...DESPITE UNFAVORABLE MID LVLS. I WILL FCST
SLGT CHC TO LOW-END CHC AFTN SHWRS AND TSTMS ACRS THE MTNS AND
FOOTHILL ZONES...WHERE DIFFERENTIAL HEATING WILL BE THE MAIN
TRIGGER. THE PIEDMONT SHUD BE LARGELY DRY.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 330 PM MONDAY...EASTERN CONUS WILL BE UNDER THE INFLUENCE OF A
MEAN RIDGE WHICH WILL GIVE THE AREA TEMPERATURES AROUND 5 DEGREES
ABOVE NORMAL.  A WELL-DEFINED SMALL SHORTWAVE CURRENTLY OVER
INDIANA...WHICH IS CLEARLY SEEN IN WV IMAGERY...WILL PROVIDE SOME
ENHANCED CHANCES FOR THUNDER STORMS...ESPECIALLY OVER HIGHER
TERRAIN...THROUGH THURSDAY.  DUE TO THE ISOLATION OF THE INDIANA
SHORTWAVE FROM THE MEAN FLOW...PREDICTIONS OF ITS MOVEMENT MAY BE
SOMEWHAT INACCURATE...HOWEVER...MODELS SHOW SOME WEAKENING OF THE
RIDGE BY WEDNESDAY WITH THE WAVE BEING SLIGHTLY ENTRAINED INTO WHAT
BECOMES BROAD WESTERLY FLOW ALOFT...WHICH MOVES THE LOBE ACROSS THE
CWA ON WEDNESDAY.  INSTABILITY IS FORECAST TO BE HIGHER OVER THE
MOUNTAINS...BUT STILL SOMEWHAT LIMITED WITH THE BEST MODEL
INSTABILITY IN THE NAM AT AROUND 1500 J/KG OF CAPE...AND HARDLY ANY
LOW-LEVEL WINDSHEAR.  WITH A LITTLE FORCING FROM THE
SHORTWAVE...SOME ISOLATED SEVERE WIND GUSTS MAY BE POSSIBLE IN THE
AFTERNOON ON WEDNESDAY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230PM MONDAY...THE EXTENDED PERIOD BEGINS ON THURSDAY NIGHT
WITH AN AMPLIFYING LONGWAVE TROUGH IN THE MID-LEVELS OVER THE
PACIFIC NORTHWEST BUILDING A DOWNSTREAM RIDGE THAT EXTENDS FROM THE
SOUTHERN PLAINS TO THE GREAT LAKES AND WELL INTO CANADA. AN EAST
COAST TROUGH AXIS EXTENDS INTO THE SOUTHEAST AND LOWER MISSISSIPPI
RIVER VALLEY WHERE A RESIDUAL CLOSED-LOW CIRCULATION REMAINS TRAPPED
UNDERNEATH THE RIDGE. HEADING INTO THE WEEKEND...THE PARENT CLOSED-
LOW CENTERED OVER LABRADOR SHIFTS INTO THE ATLANTIC AS PERSISTENT
RIDGING BUILDS OVER NEW ENGLAND...LEAVING BEHIND A WEAK TROUGH OR
CYCLONIC CIRCULATION OVER THE SOUTHEAST U.S. THAT LINGERS ACROSS THE
AREA THROUGH THE END OF THE PERIOD ON TUESDAY MORNING.
THEREFORE...THE FLOW ALOFT THROUGH THE PERIOD WILL BE HIGHLY
DEPENDENT ON THE EXACT POSITIONING OF THE RESIDUAL TROUGH...BUT
SHOULD GENERALLY BE QUITE WEAK AND TRANSITION FROM NORTHERLY TO
SOUTHEASTERLY BY TUESDAY.

AT THE SURFACE...A LARGE AREA OF HIGH PRESSURE CENTERED OVER QUEBEC
BUT EXTENDING WELL SOUTHWEST INTO TEXAS WILL GRADUALLY BUILD SOUTH
INTO NEW ENGLAND UNDERNEATH A BUILDING RIDGE ALOFT. THE HIGH
PRESSURE SYSTEM WILL ANCHOR ACROSS NEW ENGLAND THROUGH SUNDAY BEFORE
SHIFTING OFFSHORE HEADING INTO EARLY NEXT WEEK.  THE PATTERN FAVORS
THE SURFACE RIDGE AXIS NOSING SE INTO THE FORECAST AREA...RESEMBLING
A COLD-AIR DAMMING SCENARIO. THE RESULTANT NORTHEASTERLY FLOW OVER
THE WEEKEND WILL VEER EASTERLY AS THE PARENT HIGH SHIFTS OFFSHORE BY
MONDAY...BUT IN EITHER CASE THE PATTERN FAVORS UPSLOPE FLOW AND WEAK
ISENTROPIC UPGLIDE OVER THE WESTERN CAROLINAS THROUGH THE END OF THE
PERIOD.

IN TERMS OF SENSIBLE WEATHER...THE ABOVE PATTERN FAVORS CHANCE POPS
FOR SHOWERS AND GENERAL THUNDERSTORMS THROUGH THE PERIOD FOR A
MAJORITY OF THE FORECAST AREA...WITH THE HIGHEST POPS FAVORING THE
MOUNTAINS.  HIGH TEMPERATURES SHOULD BE A FEW DEGREES ABOVE NORMAL
ON FRIDAY BUT WILL DROP TO A COUPLE OF DEGREES BELOW NORMAL FOR
SATURDAY THROUGH MONDAY.  WITH INCREASED OVERNIGHT CLOUD COVER
ANTICIPATED THIS WEEKEND...EXPECT LOW TEMPERATURES TO BE SLIGHTLY
ABOVE NORMAL.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT...LOW VFR CU SCATTERING OUT AND SHUD DISSIPATE THIS EVENING.
GUIDANCE HAS BACKED OFF SIGNIFICANTLY ON CHC OF RESTRICTIONS
OVERNIGHT. THERE IS SOME MOISTURE TRAPPED UNDER A MID LEVEL
SUBSIDENCE INVERSION. HOWEVER...ANY LOW LEVEL FLOW WILL BE WLY TO
NWLY. FCST SOUNDINGS DO NOT LOOK FAVORABLE FOR FOG. THEREFORE...HAVE
GONE VFR. EXPECT LOW VFR CU TO REDEVELOP WITH HEATING TUE. LIGHT
NELY WIND THIS EVENING BECOMES CALM OVERNIGHT...THEN LIGHT NNE TUE.

ELSEWHERE...THE UPSTATE SITES WILL CLEAR OUT MORE QUICKLY THIS
EVENING. HOWEVER...STILL LITTLE CHC OF RESTRICTIONS...ALTHOUGH KAND
WOULD BE THE MOST LIKELY TO SEE MVFR FOG TOWARD DAYBREAK. LIGHT S TO
SW WIND BECOMING CALM OVERNIGHT AND LIGHT S TO SE TUE WITH FEW VFR
CU DEVELOPING. BKN CU AT HKY WILL DISSIPATE THRU THE EVENING...WITH
MVFR FOG POSSIBLE. WINDS WILL BE LIGHT. KAVL HAS THE BEST CHC OF FOG
WITH IFR LIKELY AND VLIFR POSSIBLE. SHUD SEE ANOTHER ROUND OF BKN
VFR CU THERE. CONVECTION POSSIBLE AGAIN ACROSS THE MTNS...BUT CHC
TOO LOW FOR THE TAF.

OUTLOOK...A PLUME OF GULF AND ATLANTIC MOISTURE WILL CONTINUE TO
WRAP UP ALONG THE SE COAST...GENERALLY JUST SOUTHEAST OF THE
TERMINAL FORECAST AREA...THROUGH THE WEEK. RESTRICTIONS ARE POSSIBLE
DURING PERIODS OF ANY SCATTERED SHOWERS OR THUNDERSTORMS. IN
ADDITION...LOW CLOUDS AND FOG MAY DEVELOP EACH NIGHT...ESPECIALLY IN
THE MOUNTAIN VALLEYS.

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  95%     LOW   59%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     MED   75%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH  91%     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

&&

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

&&

$$
SYNOPSIS...JMP
NEAR TERM...ARK/RWH
SHORT TERM...WJM
LONG TERM...JMP
AVIATION...RWH



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