Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030901
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
501 AM EDT THU SEP 3 2015

.SYNOPSIS...
A WEAK PRESSURE PATTERN WILL LINGER ATOP THE REGION FOR THE REST OF
THE WORK WEEK. LATE SUMMER WARMTH AND DAILY THUNDERSTORM CHANCES
WILL BE THE MAIN FEATURES OF INTEREST. A BACK DOOR COLD FRONT IS
EXPECTED TO PUSH ACROSS THE REGION ON FRIDAY FOLLOWED BY A COOL AND
MOIST AREA OF HIGH PRESSURE THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 500 AM EDT...WATER VAPOR IMAGERY SHOWS A SHORTWAVE MOVING
EASTWARD INTO THE BASE OF THE SRN APPALACHIANS THIS MORNING. HIGH
LEVEL CLOUDINESS AHEAD OF THIS WAVE CONTINUES TO KEEP MOST MORNING
FOG AND LOW CLOUD PROBLEMS AT BAY OVER THE AREA. THE UPPER FEATURE
MAY BRING SLIGHTLY ENHANCED UPWARD VERTICAL VELOCITIES THROUGH THE
SRN TIER OF THE FORECAST AREA TODAY...WITH THE BEST DEEP LAYER Q
VECTOR CONVERGENCE LIKELY CROSSING THE REGION DURING THE MORNING
HOURS. THIS TIMING WILL NOT FAVOR DEEP CONVECTIVE DEVELOPMENT...BUT
850 TO 500 MB LAPSE RATES WILL STEEPEN THROUGH THE DAY...AND SRN
TIER INSTABILITY MAY LINGER THROUGH THE MORNING HOURS WHERE HIGHER
SFC DEWPOINTS HAVE POOLED. IN ADDITION TO THIS SRN TIER
FORCING...ANOTHER ROUND OF ISOLD TO SCT RIDGE TOP SHOWER/TSRA
DEVELOPMENT IS EXPECTED WITH PEAK HEATING. ANY ACTIVITY THAT
DEVELOPS IN THE MARGINALLY UNSTABLE PROFILES MAY DRIFT OFF THE BLUE
RIDGE INTO THE ADJACENT FOOTHILLS IN NW FLOW ALOFT LATER THIS AFTN
OR EARLY EVENING...BUT DEWPOINT MIXING SHOULD LIMIT POTENTIAL
FARTHER OUT INTO THE PIEDMONT. DESPITE MID AND HIGH CLOUDS
INHIBITING HEATING SOMEWHAT TODAY...PLENTY OF LOWER 90S TEMPERATURES
ARE STILL EXPECTED EAST OF THE MTNS THIS AFTERNOON.

ANY LINGERING SHOWER ACTIVITY SHOULD GENERALLY WANE TONIGHT WITH THE
LOSS OF INSTABILITY AND THE PERSISTENT N TO NE FLOW FROM SFC HIGH
PRESSURE TO THE N. ADDITIONAL 500 MB SHORTWAVE ENERGY WILL DROP SE
TOWARD THE SRN APPALACHIANS OVERNIGHT...BUT WITH LIMITED MOISTURE.
WILL CONFINE ANY OVERNIGHT SLIGHT CHANCES OF PRECIPITATION TO THE
NRN MOUNTAINS.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
AS OF 245 AM THURSDAY...THE H5 RIDGE WILL BUILD ACROSS THE GREAT
LAKES REGION WITH A BROAD TROUGH ACROSS THE SOUTHEAST CONUS. THE
CENTER OF A 1025+MB HIGH IS FORECAST TO DEVELOP ACROSS THE NEW
ENGLAND STATES...RIDGING SOUTHWEST ACROSS THE MID AND SOUTHERN
ATLANTIC STATES. A BACK DOOR COLD FRONT IS EXPECTED TO REACH THE
PIEDMONT AND FOOTHILLS DURING THE DAYLIGHT HOURS. THE COMBINATION OF
WIDESPREAD WEAK INSTABILITY AND A ADVANCING SFC BOUNDARY SHOULD
TRIGGER SCT SHRA AND TSRA...ESPECIALLY NEAR THE EAST FACING SLOPES.
I WILL FORECAST POPS TO RANGE FROM NEAR 40 TO 50 PERCENT NEAR THE
EAST FACING SLOPES TO AROUND 30 PERCENT EAST. USING A BLEND OF
PREFERRED GUIDANCE...I WILL INDICATE HIGHS RANGING FROM THE MID 80S
WITHIN THE MTN VALLEYS TO LOW 90S EAST. THE GFS SHOWS A ELONGATED H5
H5 VORT SLIDING OVER THE REGION FRIDAY NIGHT. THE COMBINATION OF
LINGERING INSTABILITY AND THE PASSAGE OF THE MID LEVEL DISTURBANCE
SHOULD YIELD SCT SHRAS AND TSRA OVERNIGHT.

ON SATURDAY...GFS INDICATES THAT PIEDMONT WINDS WILL STRENGTHEN TO
MARGINALLY GUSTY NE WINDS AFTER SUNRISE SATURDAY. THE NE WINDS...BKN
SKY COVER...SCT TO NUM SHRA/TSRA...SHOULD PROVIDE COOLER
TEMPERATURES ON SATURDAY. THE 2M TEMPS FROM THE ECMWF AND GFS HAVE
HIGH TEMPERATURES IN THE LOW 80S ON SAT. I WILL MAINTAIN COOL HIGH
FOR SAT...GENERALLY 1 TO 2 DEGREES WARMER THAN THE RAW MODEL VALUES.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 3 AM THURSDAY...ON SUNDAY...NE WINDS APPEAR AS STRONG AS
SAT...BUT CLOUD COVER APPEARS THINNER. HIGH TEMPS WILL REMAIN BELOW
NORMAL...BUT LIKELY 1 TO 2 DEGREES WARMER THAN SAT. ON MONDAY...THE
SFC HIGH CENTER SHIFTS OVER THE WESTERN ATLANTIC...RESULTING IN
WEAKER WINDS ACROSS THE REGION. I WILL LIMIT CHC POPS TO THE
MTNS...FOOTHILLS....AND UPPER SAVANNAH RIVER VALLEY. HIGHS TEMPS MAY
RANGE WITHIN A COUPLE OF DEGREES OF NORMAL ON MON. ON TUESDAY...MID
LEVEL RIDGE WILL BUILD ACROSS THE DEEP SOUTH OVER THE SOUTHEAST
CONUS...WITH A BROAD SFC HIGH ACROSS THE SOUTHERN APPALACHIAN
REGION. FORECAST SOUNDINGS INDICATE WEAK LAPSE RATES WITHIN THE MID
LEVELS...YIELDING WEAK VALUES OF INSTABILITY. I WILL INDICATE
DIURNAL SCHC TO CHC POPS...WITH COVERAGE FAVORING THE MTNS. HIGHS
SHOULD RANGE VERY CLOSE TO NORMAL. ON WEDNESDAY...THE H5 RIDGE IS
EXPECTED TO STRENGTHEN ACROSS THE SOUTHEAST...RESULTING IN MILD MID
LEVEL TEMPS ACROSS THE CWA. HIGH TEMPERATURES WILL LIKELY RANGE
WITHIN A DEGREE OR TWO OF NORMAL. HOWEVER...CAPE VALUES MAY REMAIN
LESS THAN 1000 J/KG DUE TO THE WARM TEMPS ALOFT. I WILL FORECAST
DIURNAL SCHC TO CHC POPS...COVERAGE FAVORED OVER THE MTNS.

&&

.AVIATION /09Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...MID AND HIGH LEVEL MOISTURE AHEAD OF AN
APPROACHING SHORTWAVE WILL PROVIDE OCCASIONAL ALTOCUMULUS AND CIRRUS
CIGS THROUGH MUCH OF THE PERIOD...BUT WITH LOWER CONVECTIVE CUMULUS
SLOW TO BUILD WITH DEWPOINT MIXING EXPECTED ONCE AGAIN TODAY. THE
BEST PRECIPITATION CHANCES DURING THE TAF PERIOD WILL BE ASSOCIATED
WITH THE UPPER LEVEL SHORTWAVE CROSSING THE SRN TIER OF THE TERMINAL
FORECAST AREA TODAY...AND WITH SCATTERED RIDGE TOP DEVELOPMENT OVER
THE HIGHER TERRAIN. CONFIDENCE IS TOO LOW TO FEATURE ANY SHRA/TSRA
AT THE TERMINALS YET. EXPECT MAINLY LIGHT NW TO NE WINDS THROUGHOUT
DURING THE PERIOD...POSSIBLY TOGGLING WEST NEAR KAND THIS AFTN AND
EVENING.

OUTLOOK...A PATTERN OF DIURNAL ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS IS EXPECTED TO CONTINUE THROUGH FRIDAY. BY THE
WEEKEND...A MOIST EASTERLY FLOW SHOULD DEVELOP...BRINGING BETTER
CHANCES FOR SHOWERS AND RESTRICTIONS. LOW CLOUDS AND FOG WILL BE
POSSIBLE EACH NIGHT IN THE MOUNTAIN VALLEYS.

CONFIDENCE TABLE...

            09-15Z        15-21Z        21-03Z        03-06Z
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

&&

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

&&

$$
SYNOPSIS...NED
NEAR TERM...HG
SHORT TERM...NED
LONG TERM...NED
AVIATION...HG



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