Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 300216 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1016 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/...
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AS OF 10 PM...ONE PATCH OF SHOWERS/STORMS REMAINS OVER CALDWELL AND ALEXANDER COUNTIES...MOVING SLOWLY OFF TO THE N/NW. WILL KEEP AN AREA OF CHANCE POP INTO THE LATE EVENING TO ACCT FOR THIS AND DECREASE IT BY MIDNIGHT OR SO. STILL POSSIBLE THAT THE LIGHT SE UPSLOPE FLOW COULD TRIGGER A FEW SHOWERS TOWARD DAYBREAK NEAR THE BLUE RIDGE. EXPECT SOME LOW CLOUD REDEVELOPMENT IN THE UPSLOPE AREAS ALONG/E OF THE BLUE RIDGE IN THE PRE-DAWN HOURS. TEMPS LOOK OK. REMAINDER OF PREVIOUS DISCUSSION... 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.
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&& .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 /02Z SATURDAY THROUGH WEDNESDAY/...
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AT KCLT...SHOWER ACTIVITY IS EXPECTED TO REMAIN TO THE N/NW OF THE AIR FIELD AS THE ONGOING RADAR ECHOES WILL BE PUSHED AWAY BY A SE WIND. THE BALANCE OF THE NIGHT IS EXPECTED TO BE VFR WITH A LIGHT S OR SE WIND. THE MODEL GUIDANCE SHOWS THE DEVELOPMENT OF A NEW LOW CLOUD DECK JUST BEFORE DAYBREAK MOVING UP FROM THE SE AND FORCED DUE TO WEAK UPGLIDE. THE MODEL TREND IS TO BRING THIS IN AS A MVFR/IFR CEILING...SO THE TAF REFLECTS THIS MORE PESSIMISTIC THINKING...ALTHO THE CEILING IS KEPT LOW MVFR FOR NOW...AND CONFIDENCE IS ONLY MODEST AT BEST. THE CEILING WILL GRADUALLY LIFT AND THEN SCATTER THRU THE MORNING. EXPECT CONDITIONS TO IMPROVE TO VFR BY 15Z OR SO...WITH A LIGHT S/SE WIND. ELSEWHERE...A SHOWER COULD IMPACT KHKY THRU 01Z OR SO AND WILL BE WATCHED FOR RESTRICTIONS. AT THE MOMENT THE SHOWER IS MOVING SLOWLY SO WILL ONLY GO VCSH FOR NOW. KHKY AND KAVL COULD SEE SOME FOG DEVELOPMENT IN THE PRE-DAWN HOURS...SO THAT WAS INCLUDED BECAUSE OF RECENT NEARBY RAINFALL THIS AFTERNOON. THE FOG SHOULD BURN OFF QUICKLY AFTER SUNRISE SATURDAY. THE UPSTATE SC TERMINALS SHOULD BE VERY SIMILAR TO KCLT WITH MINOR TIMING DIFFERENCES AND THE POSSIBILITY OF BRIEF FOG RESTRICTIONS AT KAND. WIND SHOULD BE LIGHT FROM THE SE TO S. 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... 02-08Z 08-14Z 14-20Z 20-00Z KCLT HIGH 100% HIGH 100% HIGH 84% HIGH 100% KGSP HIGH 100% HIGH 93% HIGH 81% HIGH 100% KAVL HIGH 100% HIGH 97% HIGH 100% HIGH 100% KHKY HIGH 100% HIGH 100% HIGH 87% HIGH 100% KGMU HIGH 100% HIGH 90% HIGH 85% HIGH 100% KAND HIGH 100% HIGH 91% HIGH 82% 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
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...LEV NEAR TERM...JDL/PM SHORT TERM...JAT LONG TERM...LEV AVIATION...PM

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