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000
FXUS62 KGSP 200928
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
528 AM EDT MON MAY 20 2013

.SYNOPSIS...
A WEAK UPPER LEVEL TROUGH WILL REMAIN OVER THE REGION THROUGH
TUESDAY. THE FORECAST AREA WILL REMAIN IN A MOIST AND RATHER
UNSTABLE AIRMASS...BEFORE A COLD FRONT CROSSES THROUGH LATE IN THE
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
0930 UTC UPDATE...POPS HAVE BEEN RASIED IN THE NORHERN NC MOUTNAINS
PER RADAR TRENDS. WINDS WERE UPDATED TO INCORPORATE THE 06Z NAM
DATA. SKY COVER WAS RAISED PER OBSERVATIONS.

AT 300 AM EST MONDAY...AN UPPER LOW OVER THE CENTRAL APPALACHIANS
WILL DRIFT SLOWLY EAST TODAY AND TONIGHT...WHILE AN ASSOCIATED
TROUGH MOVES FROM THE FOOTHILLS TO THE PIEDMONT OF OUR AREA. THIS
WILL RESULT IN THE BEST COVERAGE OF POPS SHIFTING EAST WITH
TIME...BUT WILL ALSO RESULT IN BETTER AFTERNOON INSTABILITY
DEVELOPING ACROSS THE AREA AS THICKER AND GREATER CLOUD COVER SHIFTS
EAST. MORNING FOG AND STRATUS WILL BE SLOW TO ERODE IN THE MOIST AIR
MASS OVER OUR AREA...BUT THE MODELS SHOW DRIER AIR MOVING IN FROM
THE WEST THIS MORNING...WHICH SHOULD ALLOW FOR EROSION OF
RESTRICTIONS BY MIDDAY. MODEL SOUNDING SUGGEST A VERY WEAK LOW LEVEL
CAP WILL BE PRESENT TODAY...BUT THE CAP IS SO WEAK THAT CHANCE POPS
WILL BE CARRIED ACROSS THE AREA. WITH DRY ALOFT FOR EVAPORATIVE
COOLING...AND INCREASING WIND SHEAR INCREASING...THE POSSIBILITY OF
SEVERE THUNDERSTORMS WILL EXIST...MAINLY THIS AFTERNOON AND EVENING.
LIGHT SOUTHERLY FLOW INTO THE BLUE RIDGE WILL PROVIDE AN UPSLOPE
COMPONENT AND ENHANCE PRECIPITATION THERE. HIGH TEMPERATURES TODAY
WILL BE RANGE FROM ABOVE NORMAL IN THE MOUNTAINS TODAY AS AN UPPER
RIDGE ADVANCES...TO NEAR NORMAL IN THE FOOTHILLS...AND A BIT BELOW
NORMAL IN THE PIEDMONT NEAREST THE UPPER TROUGH AXIS. MINIMUM
TEMPERATURES WILL BE ABOVE NORMAL AS HEIGHTS RISE ALOFT.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 330 AM MONDAY...GUIDANCE NOW SHOWS ENERGY FROM THE UPPER TROF
CURRENTLY OVER THE AREA REMAINING IN PLACE FOR TUE EVEN AS AN UPPER
RIDGE TRIES TO BUILD. WHILE THE FORCING WILL NOT BE THAT STRONG...
THERE IS NOW A LACK OF A SUBSIDENCE INVERSION. MODERATE INSTABILITY
DEVELOPS DURING THE AFTERNOON. THIS SHUD LEAD TO ANOTHER DAY OF SCT
CONVECTION...WITH SLIGHTLY BETTER CHC OVER THE MTNS AND WRN CWFA
WHERE INSTABILITY IS BETTER. CONVECTION WILL LINGER A LITTLE LONGER
OVER THE MTNS TUE NITE...BUT IT SHUD STILL BE MAINLY DIURNAL IN
NATURE. HIGHS WILL BE 5 TO 10 DEGREES ABOVE NORMAL AND LOWS AROUND 5
DEGREES ABOVE.

ANY ATTEMPT AT RIDGING ENDS WED AS A TROF ROTATING AROUND ANOTHER
UPPER LOW MOVES INTO THE AREA. ALTHOUGH INSTABILITY WILL NOT BE AS
STRONG...FORCING WILL BE MUCH BETTER. THEREFORE...EXPECT NUMEROUS
COVERAGE OF CONVECTION OVER THE MTNS AND HIGH SCT ELSEWHERE BY
AFTERNOON. CONVECTION STILL LOOKS TO BE MAINLY DIURNAL AS THE TROF
AND FORCING MOVE EAST OF THE AREA OVERNIGHT. ALTHOUGH INSTABILITY
WILL BE LESS...SHEAR AND FORCING WILL BE HIGHER...SO ISOLATED SVR
STORMS ARE POSSIBLE. HIGHS WILL BE A FEW DEGREES LOWER...WHILE LOWS
WILL BE NEARLY STEADY.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 400 AM MONDAY...GFS AND ECMWF IN GOOD AGREEMENT ON AN UPPER
TROF MOVING INTO THE AREA THU AND ACROSS THE AREA FRI. THIS LEADS TO
SCT MAINLY DIURNAL CONVECTION EACH DAY. HIGHS THU ABOUT 5 DEGREES
ABOVE NORMAL AND NEAR TO SLIGHTLY ABOVE NORMAL FRI. LOWS ABOUT 5
DEGREES ABOVE NORMAL THU NITE AND NEAR NORMAL FRI NITE.

WEAK RIDGING BUILDS IN SAT WITH SHORT WAVES MOVING BY JUST NORTH OF
THE AREA SUN. AT THE SFC...THE GFS SHOWS DRY HIGH PRESSURE SAT AND
SUN. THE PREV ECWMF WAS WET FOR THE WEEKEND. HOWEVER...THE LATEST
RUN SHOWS A MAINLY DRY BACK DOOR COLD FRONT MOVING IN ON SUN.
THEREFORE...HAVE GONE WITH A DRY FCST BOTH DAYS. HIGHS AND LOWS WILL
BE NEAR NORMAL BOTH DAYS.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
AT KCLT...SHOWER ACTIVITY AROUND THE FIELD IS EXPECTED TO DIMINISH
OVERNIGHT AS INSTABILITY DECREASES. LIFR CIG AND MVFR VSBY SHOULD
PERSIST...WITH VSBY POSSIBLY DIPPING TO IFR AROUND DAWN. VFR MAY BE
SLOW TO RETURN AFTER DAWN...BUT WITH MORE BREAKS IN CLOUDS EXPECTED
MONDAY...HEATING WILL EVENTUALLY ERODE RESTRICTIONS. AFTERNOON
CONVECTIVE CHANCES LOOK BETTER MONDAY WITH GREATER INSTABILITY...
EVEN THOUGH THE PRECIPITATION COVERAGE WILL BE LOWER AS THE UPPER
SYSTEM DRIFTS EAST. LIGHT SOUTH WINDS WILL PREVAIL.

ELSEWHERE...ONLY KHKY FACES THE POTENTIAL FOR OVERNIGHT SHOWERS AS
INSTABILITY DECREASES. GUIDANCE SUPPORTS MVFR FOG AT ALL SITES BUT
KAVL...WHERE IFR IS SUPPORTED...AND LIFR CIGS AT ALL SITES BEFORE
DAWN. GUIDANCE IS SLOW TO ERODE RESTRICTIONS...BUT WITH THE UPPER
SYSTEM DRIFTING EAST...BETTER HEATING SHOULD RESULT IN EROSION OF
RESTRICTIONS BY LATE MORNING. MORE BREAKS IN CLOUDS SHOULD RESULT IN
GREATER INSTABILITY...AND BETTER AFTERNOON CONVECTIVE CHANCES. LIGHT
AND VARIABLE WINDS WILL BECOME SOUTHERLY DURING THE DAY IN THE
FOOTHILLS...AND AND BRIEFLY NORTHERLY IN THE MOUNTAINS BEFORE
BECOMING SOUTHERLY.

OUTLOOK...SCATTERED SHOWERS AND THUNDERSTORMS...AND ASSOCIATED
RESTRICTIONS...ARE EXPECTED TO CONTINUE DURING THE WEEK...BUT SHOULD
BECOME MORE FOCUSED DURING THE AFTERNOON AND EVENING.

CONFIDENCE TABLE...

            09-15Z        15-21Z        21-03Z        03-09Z
KCLT       HIGH  86%     HIGH  94%     HIGH 100%     HIGH 100%
KGSP       HIGH  85%     HIGH  96%     HIGH 100%     HIGH 100%
KAVL       HIGH  82%     HIGH 100%     HIGH 100%     HIGH  89%
KHKY       HIGH  88%     HIGH  97%     HIGH 100%     HIGH 100%
KGMU       HIGH  92%     HIGH  95%     HIGH 100%     HIGH 100%
KAND       HIGH  84%     HIGH  98%     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...RWH
NEAR TERM...JAT
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...JAT