Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 010219 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1019 PM EDT TUE MAR 31 2015 .SYNOPSIS... HIGH PRESSURE WILL SLIDE EAST OF THE AREA TONIGHT AS A WEAK COLD FRONT PASSES OVER THE CAROLINAS OVERNIGHT. SURFACE RIDGING WILL QUICKLY BUILD AGAIN FOR WEDNESDAY WHILE PRECIPIATION CHANCES INCREASE ON THURSDAY AS MOIST SOUTHERLY FLOW RETURNS. YET ANOTHER COLD FRONT IS EXPECTED TO APPROACH THE CAROLINAS FRIDAY EVENING WITH HIGH PRESSURE RETURNING FOR THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... 0215 UTC UPDATE...POPS WERE UPDATED BASED ON RADAR TRENDS IN NE GA AND WESTERN UPSTATE SC...RESULTING IN GREATER COVERAGE OVER THOSE AREAS. AS OF 230 PM...LATEST SATELLITE IMAGES INDICATED SUNNY CONDITIONS ACROSS THE FORECAST AREA...A FEW CU OVER GRAHAM COUNTY. LATEST MESOSCALE ANALYSIS INDICATE THAT THE FORECAST AREA WAS CAPE FREE. HOWEVER...LOW VALUES EXISTED ACROSS EASTERN TN SOUTH ACROSS AL AND NW GA. RECENT RUNS OF CAMS INDICATE THAT CONVECTION THE DEVELOP ALONG AN OLD FRONT ACROSS THE I-20 CORRIDOR WILL TRACK SOUTHEAST...MISSING THE UPPER SAVANNAH RIVER VALLEY. GIVEN THE CURRENT SATELLITE TRENDS...IT APPEARS THE CAMS ARE CORRECT. OTHERWISE...DEEP MIXING SHOULD PROVIDE GUSTS AROUND 20 KTS THROUGH EARLY THIS EVENING. WINDS SHOULD DECOUPLE AROUND 1Z...SETTLING FROM THE SW SLIGHTLY BELOW 10 KTS. TONIGHT...NEAR TERM MODELS INDICATE THAT A COLD FRONT ASSOCIATED WITH A MID ATLANTIC CLIPPER WILL REACH THE SOUTHERN APPALACHIANS AROUND 0Z...PASSING SOUTH OF THE NC/SC LINE BY 6Z. AS THE FRONT ENCOUNTERS THE MTNS THIS EVENING...WEAK CAPE MAY POOL ACROSS THE TN BORDER COUNTIES OF NC. THE 12Z 4KM WRF INDICATES THAT WEAK SHOWERS/THUNDERSTORMS DEVELOP ALONG THE SPINE OF THE APPALACHIANS BETWEEN 3Z TO 8Z. THE NAM AND GFS ARE GENERALLY ON BOARD WITH THE 4 KM WRF. HOWEVER...GIVEN LOW DEWPOINTS AND NEARLY ZERO CAPE THIS AFTERNOON...I ASSUME THAT INSTABILITY WILL STRUGGLE TO EXIST PAST MIDNIGHT. I WILL INDICATE CHC TO SCHC ACROSS THE TN BORDER COUNTIES THIS EVENING...WITH NO MENTION AFTER 5Z. FOG WILL BE POSSIBLE ANYWHERE THAT RAIN FALLS. LOW TEMPERATURES ARE FORECAST TO RANGE FROM THE U30S TO LOW 40S ACROSS THE MTNS TO AROUND 50 ACROSS THE UPSTATE AND NE GA. WEDNESDAY...WEAK HIGH PRESSURE SHOULD BUILD SOUTH ACROSS THE WESTERN CAROLINAS DURING THE DAYLIGHT HOURS. LIGHT NORTH-NORTHEAST WINDS ARE FORECAST TO DEVELOP DURING THE PRE DAWN HOURS AND REMAIN THROUGH THE DAY. RISING MID LEVEL HEIGHTS AND LINGERING LOW BL DEWPOINTS WILL YIELD DRY CONDITIONS ACROSS THE REGION. HIGH TEMPERATURES SHOULD RANGE FROM THE MID 60S WITHIN THE MTN VALLEYS TO LOW TO MID 70S ALONG AND EAST OF I-85. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... AS OF 300 PM EDT TUESDAY...SHORT TERM BEGINS WITH RISING THICKNESSES ACROSS THE SOUTHEAST AS WEAK RIDGING ALOFT BUILDS IN. NORTHWEST FLOW OVER THE WESTERN CAROLINAS WILL HELP TO PUSH THE SURFACE HIGH PRESSURE FARTHER OFFSHORE AS ANOTHER SHORTWAVE DIGS INTO THE MID SOUTH. WAVETRAIN SLIDES QUICKLY EAST DURING THE DAY ON THURSDAY AND SHORTWAVE DAMPS SOMEWHAT AS IT PUSHES INTO THE SOUTHEAST...BUT STILL ENOUGH FOR ALL GUIDANCE TO DEVELOP SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN APPALACHIANS. FINGER OF STABILITY PERSISTS JUST IN THE LEE OF THE MOUNTAINS BUT BOTH NAM AND GFS INCREASE SBCAPE VALUES ACROSS UPSTATE SOUTH CAROLINA AND NORTHEAST GEORGIA... WITH NAM PUSHING UPWARDS OF 2000 J/KG. GFS SUBSTANTIALLY LOWER THAN THAT WITH ONLY LIMITED SBCAPE VALUES PUSHING INTO THE FORECAST AREA. HAVE TRIED TO REFLECT A COMPROMISE WHICH SEEMS TO BE IN DECENT AGREEMENT WITH SPC DAY3 CONVECTIVE OUTLOOK...BRINGING GENERAL THUNDER INTO THE WEST AND SOUTHWEST PORTIONS OF THE FORECAST AREA. WEAK DEEP-LAYER SHEAR /GENERALLY LESS THAN 35KT 0-6KM/ COINCIDES WITH THESE ENCROACHING SBCAPE VALUES SO WHILE AT THIS TIME SEVERE THUNDERSTORMS ARE NOT ANTICIPATED...EVOLUTION OF THE SHORTWAVE WILL HAVE TO BE MONITORED IN SUBSEQUENT FORECASTS. SHOULD SEE A BIT OF LOWERING HIGH TEMPS FOR THURSDAY AFTERNOON IN RESPONSE TO THE FALLING HEIGHTS ASSOCIATED WITH THE SHORTWAVE ITSELF AS WELL AS INCREASED CLOUD COVER. SHORTWAVE PUSHES THROUGH THURSDAY NIGHT INTO FRIDAY MORNING LEAVING WEAK NEAR ZONAL FLOW ALOFT OVER THE AREA ON FRIDAY. SOUTHERLY SURFACE FLOW WILL CONTINUE TO PUMP MOISTURE ESPECIALLY INTO THE PIEDMONT WITH HIGHS AGAIN REACHING WELL ABOVE SEASONAL NORMALS ACROSS THE AREA. MEANWHILE ANOTHER MORE SIGNIFICANT TROUGH DIPS OUT OF CANADA INTO THE MIDWEST AND GREAT LAKES...DRAGGING A COLD FRONT ALONG WITH IT. SOME CONCERN STILL ON TIMING WITH THE GFS 6-12 HOURS FASTER THAN THE ECMWF /THIS HAS BEEN THE TREND FOR THE PAST FEW RUNS/ BUT IN ANY CASE SHOULD START TO SEE AN INCREASE IN POPS LATE IN THE SHORT TERM PERIOD ESPECIALLY ACROSS THE MOUNTAINS AS THE INFLUENCE OF THE FRONT PUSHES INTO THE FORECAST AREA. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 330 AM EDT TUESDAY...THE MEDIUM RANGE FCST PERIOD INITIALIZES FRIDAY MORNING AHEAD OF A COLD FRONT PUSHING SOUTHEAST THROUGH THE OH VALLEY INTO THE TN VALLEY REGION. A SURFACE WAVE DEVELOPING ALONG THE FRONTAL AXIS WILL DEEPEN AS SOUTHERLY FLOW OVER THE SOUTHEAST SETS UP AN IMPROVING WARM SECTOR WHERE DEWPOINTS ARE FCST TO SURGE INTO THE UPPER 50S TO LOWER 60S WITH SURFACE TEMPERATURES FCST IN THE 70S TO NEAR 80. AS DIURNAL HEATING MAXIMIZES...WOULD NOT BE SURPRISED TO SEE SCATTERED CONVECTION ON FRIDAY AHEAD OF THE FRONT...AS DEPICTED ON BOTH THE GFS/ECMWF. THAT SAID...MODELS FAVOR QUITE A BIT OF MOISTURE IN THE MID/UPPER LEVELS LIMITING LAPSE RATES...THUS DAMPENING THE POTENTIAL FOR DEEP/ORGANIZED CONVECTION DESPITE MODEST SHEAR THROUGH THE PROFILE. FCST FEATURES CHANCE LEVEL POPS ACROSS THE EAST WHILE INCREASING LIKELY POPS ARE FAVORED OVER THE MTNS WITH THUNDER MENTIONED REGIONWIDE. THE FRONT WILL PUSH THROUGH THE REGION DURING THE EVENING HOURS WITH AN ADDITIONAL ROUND OF SHOWERS/THUNDERSTORMS POSSIBLE ALONG AND JUST BEHIND THE FRONTAL AXIS. BY THAT TIME EXPECTING INSTABILITY TO BE AT A PREMIUM THEREFORE ONLY ISOLATED/SCATTERED THUNDERSTORMS LOOK FEASIBLE AT THAT POINT. HIGH PRESSURE WILL SPILL IN SHARPLY ON SATURDAY MORNING FROM THE WEST LEADING TO A DRYING FCST FOR THE REMAINDER OF THE WEEKEND AMONGST NEAR NORMAL TEMPERATURES AND MOSTLY SUNNY SKIES. THE NEXT ROUND OF WEATHER IS FCST ON MONDAY AS ANOTHER WEAK SHORTWAVE SLIDES THROUGH THE TN VALLEY INTO THE SOUTHERN APPS. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... AT KCLT...VFR. SKY COVER WILL INCREASE SOMEWHAT OVERNIGHT AS A COLD FRONT APPROACHES...BUT NOT ENOUGH FOR A LOW VFR CIG. THE WIND WILL VEER FROM SW TO NW TONIGHT...AND NE BY DAYBREAK...BUT WILL REMAIN RATHER LIGHT. MODEL GUIDANCE DOES NOT SUPPORT A VSBY RESTRICTION. ELSEWHERE...VFR. SKY COVER WILL INCREASE AHEAD OF AN APPROACHING FRONT...BUT ENOUGH FOR A LOW VFR CIG AT KAVL ONLY. FOOTHILLS WINDS WILL VEER FROM SW TO NW THIS EVENING...THEN NE BY DAWN....AND SE ON WEDNESDAY AFTERNOON. KAVL WINDS WILL BO NW EARLY AND REMAIN THERE UNTIL WEDNESDAY AFTERNOON WHEN THEY GO SE AS WELL. OUTLOOK...AN APPROACHING WARM FRONT AND RESULTANT MOISTURE RETURN WILL BRING BETTER CHANCES FOR PRECIP/RESTRICTIONS ACROSS THE AREA LATER IN THE WEEK...PERHAPS STARTING THURSDAY MORNING. A COLD FRONT WILL AFFECT THE AREA FRIDAY INTO EARLY SATURDAY...BRINGING ANOTHER ROUND OF RAIN/POSSIBLE THUNDERSTORMS AND RESTRICTIONS. VFR WILL RETURN FOR THE REST OF THE WEEKEND. CONFIDENCE TABLE... 02-08Z 08-14Z 14-20Z 20-00Z 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_TABLES && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...JPT NEAR TERM...JAT/NED SHORT TERM...TDP LONG TERM...TDP AVIATION...NED

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