Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 292049
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
449 PM EDT FRI MAY 29 2015

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL PERSIST ACROSS THE REGION THROUGH THE
WEEKEND AND INTO EARLY NEXT WEEK...WITH MOIST SOUTHERLY FLOW FUELING
SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS.SATURDAY
WILL BE THE DRIEST DAY OF THE WEEKEND...BEFORE A COLD FRONT
APPROACHES THE AREA BY TUESDAY AND STALLS OUT THROUGH THE MIDDLE OF
NEXT WEEK...KEEPING RAIN CHANCES ABOVE AVERAGE. A SLOW DRYING
OUT/WARMING TREND IS EXPECTED BY THE END OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 430 PM...STILL SEEING SCATTERED SHOWERS POPPING UP MAINLY OVER
THE MTNS AND ADJACENT FOOTHILLS. SOME NEW ACTIVITY WAS NOTED NEAR
THE SC BLUE RIDGE. THINK THE CURRENT FCST HAS A VERY GOOD HANDLE ON
THE CONVECTIVE ACTIVITY SO ONLY MINOR COSMETIC CHANGES WILL BE MADE.
TEMPS LOOK GOOD AS WELL.

PREVIOUS DISCUSSION...

SCATTERED SHOWERS CONTINUE TO COVER MUCH OF THE NW HALF OF THE CWA
EARLY THIS AFTERNOON...AS A BOUNDARY OF ATLANTIC ORIGIN CONTINUES TO
PUSH NORTHWEST ACROSS THE AREA. MEANWHILE...DEWPOINTS HAVE CRASHED
BEHIND THIS BOUNDARY ACROSS THE SC MIDLANDS AND CTRL NC. DRIER LOW
LEVEL AIR SHOULD GRADUALLY FILTER INTO OUR PIEDMONT ZONES THROUGH
THE AFTERNOON...RESULTING IN MINIMAL BUOYANCY. POPS WILL THEREFORE
DIMINISH FROM SOUTHEAST TO NORTHWEST WITH TIME THIS PM. CELLS HAVE
THUS FAR BEEN MOVING RIGHT ALONG. THUS...LOCALIZED HYDRO ISSUES WILL
LIKELY BE LIMITED TO LOCATIONS THAT MANAGE TO RECEIVE SOME TRAINING
CELLS...ESP OVER AND NEAR THE HIGH TERRAIN. MODEST BUOYANCY SHOULD
KEEP THE SEVERE STORM THREAT RATHER LOW. CONVECTION SHOULD DIMINISH
QUICKLY THIS EVENING. WITH SE LOW LEVEL FLOW PERSISTING...ANOTHER
SURGE OF ATLANTIC MOISTURE IS EXPECTED TO PUSH INTO THE AREA TOWARD
DAYBREAK...AND THIS COULD RESULT IN SOME ISOLATED SHOWERS NEAR THE
ESCARPMENT...BUT WILL LIKELY BE MANIFEST MORE AS EXPANDING LOW CLOUD
COVER. MIN TEMPS WILL BE NEAR TO SLIGHTLY ABOVE NORMAL.

SATURDAY...OTHER THAN PERSISTENT WEAK UPSLOPE FLOW AND SCANT LOW
LEVEL MOISTURE...NOT MUCH TO HANG ONE/S HAT ON IN TERMS OF THE
CONVECTIVE POTENTIAL. INSTABILITY PARAMETERS FROM FORECAST SOUNDINGS
ARE RATHER PITIFUL FOR LATE MAY...OWING TO WEAK LAPSE RATES/FAIRLY
WARM TEMPS ALOFT RESULTING FROM RISING HEIGHTS. NEVERTHELESS...
THERE WILL BE SOME DEGREE OF BUOYANCY...AND COMBINATION OF UPSLOPE
FLOW/DIFF HEATING SHOULD ALLOW FOR A FEW CELLS...MAINLY IN THE FORM
OF SHOWERS TO FORM NEAR THE HIGH TERRAIN DURING THE AFTERNOON...AND
NEAR-CLIMO POPS WILL BE ADVERTISED.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AT 2 PM EDT FRIDAY...ON SATURDAY EVENING AN UPPER RIDGE WILL BE NEAR
BERMUDA...WHILE AND UPPER TROUGH WILL BE MOVING FROM THE PLAINS TO
THE MS RIVER VALLEY. THE TROUGH CROSSES THE MS RIVER VALLEY ON
SUNDAY NIGHT...REACHING THE OH AND TN RIVER VALLEYS ON MONDAY.
SHORTWAVE ENERGY MOVING THROUGH THIS TROUGH REMAINS TO OUR WEST UNTIL
MONDAY...WHEN A SHORTWAVE CROSSES THE SOUTHERN APPALACHIANS LATE IN
THE DAY.

AT THE SURFACE...A COLD FRONT WILL SLOW WHILE CROSSING THE OH AND
LOWER MS RIVER VALLEY ON SATURDAY NIGHT. THIS FRONT REACHES THE
SOUTHERN APPALACHIANS BY EARLY MONDAY...THEN MOVES VERY LITTLE
DURING THE DAY. INSTABILITY IS EXPECTED TO INCREASE ALONG AND AHEAD
OF THIS BOUNDARY ON SUNDAY...AND SHEAR IS EXPECTED TO FOLLOW SUIT ON
MONDAY...SUPPORTING AN INCREASING CHANCE OF CONVECTION. LOW LEVEL
FLOW WILL BE VEER FROM LIGHT SW ON SUNDAY...TO SLIGHTLY GREATER BUT
NEARLY PARALLEL TO THE BLUE RIDGE ON MONDAY...LIMITING THE UPSLOPE
FLOW COMPONENT. ISENTROPIC UPGLIDE WILL BE LARGELY LACKING.
PRECIPITATION AMOUNTS WILL BE GREATEST WHERE THUNDERSTORMS MOVE
SLOWLY IN WEAK SOUTHERLY STEERING FLOW ON SUNDAY...MAINLY AGAINST
THE BLUE RIDGE...AND WHERE THEY TRAIN IN BETTER SW FLOW ON SUNDAY.
TEMPERATURES WILL RUN SLIGHTLY ABOVE NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM FRIDAY...MODEL CONSISTENCY AT THE BEGINNING OF THE
MEDIUM RANGE IS RELATIVELY GOOD. THE PERIOD STARTS MONDAY NIGHT WITH
AN UPPER TROUGH AND ASSOCIATED SURFACE FRONT JUST TO THE WEST OF THE
SOUTHERN APALACHIANS...WITH A RATHER BROAD UPPER LOW OVER THE MS/LA
GULF COAST. THE FRONTAL BOUNDARY MEANDERS SLIGHTLY TO THE EAST...AND
REMAINS STALLED OVER OUR AREA THROUGH TUESDAY NIGHT. A MOIST AIRMASS
WILL REMAIN IN PLACE OVER THE CWA AHEAD OF THE FRONT...RESULTING IN
LIKELY POPS FOCUSED AROUND THE FRONTAL BOUNDARY WITH SLIGHTLY
DIURNAL TREND. A SURFACE HIGH WILL BUILD INTO THE NORTHEAST ON
WEDNESDAY...CREATING A WEDGE/CAD SETUP BY THURSDAY THAT SHOULD
REMAIN AT LEAST THROUGH FRIDAY.

MODEL DIVERGENCE BEGINS ON THURSDAY...WITH THE GFS NOW SUGGESTING A
WETTER END OF THE PERIOD THAN THE ECMWF. THE GFS MAINTAINS AN UPPER
LEVEL LOW SLOWLY LIFTING NORTHWARD FROM THE GULF COAST WHICH
WOULD PREVENT CLEARING OF THE FRONTAL BOUNDARY FROM OUR AREA...WHILE
THE ECMWF DIVES THE LOW INTO THE GULF AND ALLOWS THE FRONT AND
ITS ASSOCIATED MOISTURE TO CLEAR BY FRIDAY. WENT WITH POPS JUST
ABOVE CLIMO WITH A DIURNAL PEAK...WEIGHTING THE GFS MORE HEAVILY DUE
TO ITS BETTER RUN-TO-RUN CONSISTENCY. INSTABILTY REMAINS MEAGER
THROUGH THE EXTENDED PERIOD...SO ANY CONCERNS SHOULD BE MAINLY
LIMITED TO LOCALLY HEAVY RAINFALL ASSOCIATED WITH WEAK STEERING
FLOW/TRAINING.

MAX TEMPS WILL BE NEAR OR JUST BELOW CLIMO AT THE BEGINNING OF THE
MEDIUM RANGE...AND THE MOIST AIRMASS WILL KEEP LOWS A CATEGORY OR
TWO ABOVE CLIMO...LIMITING THE DIURNAL TEMPERATURE RANGE. HIGHS WILL
REBOUND SLIGHTLY TO NORMAL OR JUST ABOVE BY THE END OF THE PERIOD.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT/UPSTATE SC TERMINALS...WINDS SHOULD EVENTUALLY SETTLE AT SE
AT AROUND 5 KTS THIS AFTERNOON IN THE WAKE OF NW-MOVING BOUNDARY.
LOWER DEWPOINTS FILTERING INTO THE AREA BEHIND THIS BOUNDARY ARE
EXPECTED TO RESULT IN DIMINISHING CHANCES FOR CONVECTION THIS
AFTERNOON. THUS...ALL VCSH/VCTS WERE REMOVED FROM THE FORECAST.
HOWEVER...A STRAY SHOWER CANNOT BE RULED OUT...ESP OVER THE FIRST
COUPLE OF HOURS OF THE FORECAST PERIOD. OTHERWISE...ANOTHER BOUNDARY
OF ATLANTIC ORIGIN IS EXPECTED TO PUSH INTO THE AREA OVERNIGHT...
BRINGING ANOTHER WAVE OF LOW LEVEL MOISTURE. WEAK UPGLIDE/UPSLOPE
FLOW IS EXPECTED TO RESULT IN EXPANDING LOW CLOUDS TOWARD
DAYBREAK...ESP NEAR THE BLUE RIDGE/UPSTATE SC TERMINALS. THE
FORECAST HAS BEEN MAINTAINED AT LMVFR FOR NOW...BUT CANNOT RULE OUT
IFR CONDITIONS.

AT KAVL/KHKY...SHOWERS/POSSBL THUNDERSTORMS WILL PERSIST IN THE VCNY
OF THESE TWO TERMINALS FOR THE NEXT COUPLE OF HOURS...WITH DIMINISHING
CHANCES EXPECTED THEREAFTER. TEMPOS ARE CARRIED THROUGH 19/20Z FOR
SHRA AND MVFR CONDITIONS. WEAK UPGLIDE/UPSLOPE IS EXPECTED TO RESULT
IN EXPANDING LOW CLOUDS TOWARD DAYBREAK. THE FORECAST HAS
BEEN MAINTAINED AT LMVFR FOR NOW...BUT CANNOT RULE OUT IFR
CONDITIONS.

OUTLOOK...MOIST SW FLOW WILL CONTINUE TO AFFECT THE TERMINAL
FORECAST AREA THROUGH THIS WEEKEND...AS A COLD FRONT LAYS OVER TO
THE NORTH OF THE AREA. EXPECT POCKETS OF MORNING FOG AND/OR STRATUS
MOST DAYS...WITH CONTINUED CHANCES OF AFTN/EVENING SHRA/TSRA EACH
DAY.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  98%     HIGH  91%
KGSP       HIGH 100%     HIGH 100%     HIGH  84%     HIGH  85%
KAVL       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  89%
KHKY       HIGH 100%     HIGH 100%     LOW   59%     HIGH  91%
KGMU       HIGH 100%     HIGH 100%     HIGH  92%     HIGH  91%
KAND       HIGH 100%     HIGH 100%     LOW   48%     HIGH  83%

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...LEV
NEAR TERM...JDL/PM
SHORT TERM...JAT
LONG TERM...LEV
AVIATION...JDL


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