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000
FXUS62 KGSP 190215
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1015 PM EDT TUE JUN 18 2013

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL CROSS THE REGION ON WEDNESDAY...BUT
WITHOUT ENOUGH MOISTURE TO EXPECT MORE THAN ISOLATED SHOWERS. MOIST
EASTERLY FLOW WILL THEN KEEP SOME RAIN CHANCES THRU LATE WEEK MAINLY
OVER THE MOUNTAINS. HIGH PRESSURE WILL BUILD OVER THE AREA FOR THE
WEEKEND...MAINTAINING A WARM AND MOIST AIRMASS WITH A CHANCE OF
SHOWERS AND THUNDERSTORMS EACH AFTERNOON.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
930 PM UPDATE...DUE TO LARGELY BOUNDARY-PARALLEL SHEAR...CELLS THAT
INITIALLY FORMED AROUND SUNSET HAVE TRAINED ROUGHLY ALONG A
GREENVILLE TO CHESTER LINE IN CONVERGENT ZONE NEAR THE FRONT.
ACTIVITY NOW BEGINNING TO DIMINISH AS INSTABILITY WANES...BUT SOME
PRECIP LIKELY TO CONTINUE FOR ANOTHER HOUR OR SO AT LEAST. HOWEVER
WITH OUTFLOW PUSHING OUT ACRS GREENVILLE AND SPARTANBURG COUNTIES
CAN/T RULE OUT A COUPLE OF ISOLATED SHOWERS FIRING FROM THE SRN
PORTIONS OF THOSE COUNTIES SOUTH. NORTH OF THE CURRENT ACTIVITY
PRECIP CHANCES ARE TOO SMALL TO MENTION THIS EVENING. STORMS ALONG
THE UPSTREAM BOUNDARY OVER KY WOULD TAKE UNTIL AFTER MIDNIGHT TO
REACH THE TN/NC BORDER...BUT THEY ARE ALREADY STRUGGLING IN THE MORE
STABLE ENVIRONMENT THEY ARE ENTERING...SO DO NOT SEE A NEED TO
REFLECT THESE STORMS IN POPS TONIGHT. TEMPS HAVE BEEN ON TRACK SO
FAR THIS EVENING AND WILL MAINTAIN GOING LOWS.

730 PM UPDATE...PRECIP ACTIVITY NOW CONFINED TO THE PIEDMONT SHOULD
CONTINUE TO MOVE OUT OF THE CWFA WITH FRONT PUSHING INTO THAT AREA.
ACTIVITY GENERALLY WEAKENING WITH LOSS OF HEATING ANYWAY. RAP AS
WELL AS LOCAL WRF MODEL DO NOT SHOW ANY FURTHER DEVELOPMENT THIS
EVENING...AND WINDS ARE DRY AND DOWNSLOPING ANYWAY. STILL DO THINK
SOME OF THE REMAINING CU IN EAST TN AND THE MTNS OF WNC WILL REMAIN
AS PATCHY STRATUS FOR MUCH OF THE NIGHT...WITH CONVECTIVE DEBRIS
SPREADING ACROSS THE SE HALF OF THE CWFA TOO. KEPT PCLDY-MCLDY SKIES
OVERNIGHT AS A RESULT.

AS OF 230 PM EDT TUESDAY...A BIT OF A TRICKY FCST THIS AFTERNOON AND
EARLY EVENING. THE OVERALL PATTERN IS WELL AGREED UPON BY THE
MODELS...HOWEVER CONFIDENCE IN THE EVOLUTION OF S/W ENERGY ACROSS
THE CWFA IS NOT VERY HIGH DUE TO MODEL DIFFERENCES. THE LATEST RADAR
SHOWS AN UNSTABLE AIRMASS TO THE WEST BECOMING INCREASINGLY UNSTABLE
INTO THE WRN ZONES. VSBY SAY SHOW GOOD CLEARING AND HEATING TAKING
PLACE...BUT IN A DEEPLY MOIST ATMOS SBCAPE VALUES WILL LIKELY REACH
ONLY MOD LEVELS. THIS IS A LITTLE EVIDENT IN THE LOW TOP CONV SEEN
TO THE WEST. IN ANY REGARD...WILL ANTICIPATE TSTMS DEVELOPING AHEAD
OF THE WEAK COLD FRONT AND DEPENDING ON THE STRENGTH OF THE CROSS
S/W ENERGY...SOME OF THESE COULD BECOME STRONG TO SEVERE THIS
AFTERNOON. THE MAIN THREAT WOULD BE LARGE HAIL AND PERHAPS DAMAGING
WINDS AS DRIER AIR WORKS INTO THE MLVLS. EXPECT A WIND SHIFT ACROSS
THE MTNS AROUND 00Z AND INTO THE UPSTATE NEAR 05Z. THIS WILL
SUPPRESS ANY ACTIVITY TO THE SOUTH WITH A LOWER THETA/E AIRMASS
MIXING IN. SOME PATCHY DENSE FG IS POSSIBLE AROUND DAYBREAK IN THE
MTN VALLEYS AS THE PGRAD IS NOT REAL TIGHT BEHIND THE FRONT AND
BROADENS THROUGH 12Z.

A CP HIGH WILL WORK SOUTH INTO THE OH VALLEY TOMORROW AND PUSH A
BACKDOOR COLD FRONT INTO THE NRN ZONES BY THE AFTERNOON. THERE IS
NOT MUCH MOISTURE AVAILABLE WITH THIS SYSTEM SO WILL EXPECT THE BEST
PRECIP CHANCES ACROSS THE MTNS...WHERE AN E/LY UPSLOPE FLOW BRINGS
IN ATL MOISTURE. POPS HAVE BEEN HELD TO SLIGHT/CHANCE ACROSS THE
MTNS AND SLIGHT ELSEWHERE...WITH MAINLY -SHRA AND PERHAPS A MODERATE
THUNDERSTORM OR TWO ACROSS THE FHILLS AND MTNS. MAX TEMPS SHOULD
STILL BE A COUPLE DEGREES BELOW NORMAL WITH THE NE/LY SFC FLOW AND
AIRMASS MIXING.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 200 PM EDT TUESDAY...THE SHORT TERM WILL BE DOMINATED BY
SURFACE HIGH PRESSURE THAT WILL SET UP CAMP OFF THE NEW ENGLAND
COAST WHICH WILL REMAIN RIDGED SWD INTO THE SOUTHERN APPALACHIANS
THROUGH FRI. THE UPPER AIR PATTERN WILL BE ALMOST INDETERMINATE IN
THE DEEP SOUTH WITH VERY WEAK FLOW. THE AREA WILL BE BETWEEN A
TROUGH WELL TO THE NE AND AN UPPER RIDGE OVER THE SOUTHERN PLAINS.
HENCE...NO SIGNIFCANT UPPER FORCING IS ANTICIPATED. MODEL TIME
HEIGHTS INDICATE THAT MOISTURE WILL REMAIN RELATIVELY HIGH IN THE
BOUNDARY LAYER WITH DRYING ESSENTAILLY ABOVE 10KFT THROUGH THU NIGHT.
HOWEVER...MOISTURE IN THE COLUMN IS FORECAST TO DECREASE ON FRI.
HENCE...THE WEATHER SHOULD BE DRIVEN BY MAINLY BY THE LOW LEVEL WIND
FLOW AND ANY MECHANICAL LIFT IT MUSTERS...PLUS DIURNAL HEATING.
THEREFORE...MAINLY DIURNAL/SCATTERED CONVECTION IS EXPECTED PRIMARILY
OVER THE MOUNTAINS...WITH PERHAPS A DOWN TICK IN COVERAGE ON FRI
AFTERNOON DUE TO THE DRYER AIR. WITH THE WEAK UPSLOPE FLOW...SOME
NOCTURNAL WIDELY SCATTERED SHOWERS WILL REMAIN POSSIBLE OVER THE
MOUNTAINS WED/THU NIGHTS. USED AN ALLBLEND APPROACH TO TEMPERATURES
WHICH PRODUCED MAX TEMPS ON THU AND FRI ABOUT A CATEGORY BELOW
AVERAGE.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 2 PM TUESDAY...THE MAIN FEATURE FOR THE EXTENDED PERIOD IS A
RIDGE OF HIGH PRESSURE THAT WILL SET UP OVER THE SOUTHEASTERN CONUS
OVER THE WEEKEND AND INTO MONDAY. THE BERMUDA HIGH WILL REMAIN
SITUATED OVER THE ATLANTIC OFF THE EAST COAST...SETTING UP A MOIST
SOUTHEASTERLY TO SOUTHWESTERLY LOW-LEVEL FLOW REGIME FOR THE REGION.
THIS WILL DRIVE MAINLY DIURNAL CONVECTION FOR THE PERIOD...WITH
GREATER CHANCE POPS FAVORING THE HIGHER ELEVATIONS EACH AFTERNOON
THROUGH THE MIDDLE OF NEXT WEEK. THE PERSISTENT RIDGE WILL ALLOW FOR
A SLIGHT WARMING TREND...WITH TEMPS NEAR TO SLIGHTLY ABOVE AVERAGE
BY THE END OF THE EXTENDED PERIOD.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...WINDS WILL SHIFT TO NW QUADRANT THIS EVENING AS FRONTAL
BOUNDARY ARRIVES...BUT TIMING TOUGH WITH TSTM ACTIVITY ACRS THE
REGION. HAVE SETTLED ON 03Z BASED MAINLY ON GFS MOS AND NAM. SOME
SHOWERS PRIOR TO THIS TIME AS WELL THOUGH VSBY SHUD REMAIN VFR.
DRIER AIR WILL WORK IN TONIGHT BUT SOME CLOUD COVER WILL LIKELY
REMAIN GIVEN AMT OF CONVECTIVE DEBRIS AT THIS TIME JUST BEFORE
SUNSET. DOWNSLOPING ON THE NW WINDS WILL LIMIT CLOUD DEVELOPMENT AND
GUIDANCE IN DECENT AGREEMENT THAT BKN CIG WILL REMAIN VFR. THIS WILL
MIX UP TO 050-060 WED MRNG. ISOLATED -SHRA AROUND THE AREA TMRW BUT
NOT WORTHY OF A TAF MENTION. LIGHT NLY WINDS FOLLOWING SHIFT.

ELSEWHERE...SHOWER/THUNDER CHANCES VERY SMALL AT TAF SITES THIS
EVENING AS DRIER...MORE STABLE AIR PUSHES IN BEHIND A COLD FRONT.
SITES THAT HAVE NOT ALREADY SEEN SHIFT TO NW WILL SEE IT BY EARLY
WED MRNG. LEFTOVER LOW CU OVER THE MTNS MAY CONGEAL INTO A MORE
SOLID DECK THIS EVENING BUT WITH THE DRY AND DOWNSLOPING FLOW CIGS
UNLIKELY TO LOWER MUCH...SO KEPT VFR CIGS AT ALL SITES. FAIRLY
STRONG SIGNAL FROM GUIDANCE THAT SOME FOG WILL FORM IN THE
MTNS/FOOTHILLS. WENT PREVAILING MVFR WITH TEMPO IFR AT KAVL/KHKY.
MIDLEVEL CIGS EXPECTED TOMORROW WITH ENUF CU DEVELOPMENT TO EXPECT
SOME ISOLATED SHOWERS...BUT WITH COVERAGE TOO LOW TO INCLUDE IN TAFS.

OUTLOOK...MOIST EASTERLY FLOW WILL SET UP WED NIGHT LEADING TO LOW
STRATUS ACROSS MUCH OF THE AREA THU MORNING WITH RESTRICTIONS LIKELY.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   72%     HIGH  86%     HIGH 100%     HIGH 100%
KHKY       HIGH  95%     HIGH  91%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  95%     HIGH 100%     HIGH 100%
KAND       HIGH  95%     MED   72%     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_TABLES

&&

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

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...SBK/WIMBERLEY
SHORT TERM...LG
LONG TERM...VISIN
AVIATION...WIMBERLEY