Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 011048 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 648 AM EDT MON SEP 1 2014 .SYNOPSIS... SOUTHERLY FLOW INDUCED BY A PERSISTENT BERMUDA HIGH WILL CONTINUE TO PROMOTE DIURNAL SHOWERS AND THUNDERSTORMS THROUGH MUCH OF THE WEEK. A FRONTAL PASSAGE WILL OCCUR ON TUESDAY EVENING INTO WEDNESDAY MORNING WITH ANOTHER FRONT PASSING THROUGH OVER THE WEEKEND LEADING TO ENHANCED SHOWER AND THUNDERSTORM CHANCES FOR THOSE PERIODS. HIGH PRESSURE WILL ONCE AGAIN REGAIN CONTROL BY EARLY NEXT WEEK BEHIND THE ABOVE MENTIONED FRONT LEADING TO SLIGHTLY COOLER TEMPERATURES AND MORE SETTLED WEATHER. && .NEAR TERM /THROUGH TONIGHT/... AS OF 645 AM...PATCHY DENSE MTN VALLEY FOG ACROSS THE MTNS AND PATCHY FOG ELSEHWERE WILL DISSIPATE BY MID MORNING. ELSEWHERE...BKN CIRRUS THIS MORNING WITH HIGH BASED CU DEVELOPING FOR THE AFTERNOON. A FEW SHRA ACROSS THE MTNS WILL DISSIPATE BY LATE MORNING...BEFORE SCT CONVECTION RETURNS FOR THE AFTERNOON. STILL EXPECT BEST CHC TO BE ACROSS THE NC MTNS WITH ISOLATED ELSEWHERE. OTHERWISE...GOING FCST LOOKS ON TRACK WITH ONLY MINOR CHANGES. AS OF 305 AM...UPPER RIDGE AND SFC BERMUDA HIGH WILL REMAIN IN PLACE TODAY AND TONIGHT. HOWEVER...A SHORT WAVE WILL BRUSH BY THE MTNS TODAY. THIS MAY BE JUST ENUF FORCING TO ACT ON THE DEVELOPING INSTABILITY AND DIFFERENTIAL HEATING TO PRODUCE LOW END SCT CONVECTION ACROSS MOST OF THE NC MTNS...THE FRENCH BROAD VALLEY BEING THE MAIN EXCEPTION WHERE ISOLATED COVERAGE EXPECTED. OUTSIDE OF THE NC MTNS...ATMOS WILL REMAIN CAPPED MOST OF THE DAY WITH ONLY WEAK INSTABILITY DEVELOPING LATE IN THE AFTERNOON WITH RELATIVELY HIGH LFC LEVELS. THERE WILL BE LITTLE IN THE WAY OF FORCING AS LEE TROF SETS UP EAST OF THE CWFA. HAVE LOW END ISOLATED CONVECTION OVER THIS AREA. IN FACT...THERE MAY NOT BE ANY CONVECTION AT ALL ALONG AND SOUTH OF THE I-85 CORRIDOR...BUT WILL MAINTAIN CONSISTENCY WITH THE LOW END ISOLATED POP. HIGHS WILL AGAIN WELL ABOVE NORMAL. CONVECTION WILL DISSIPATE THRU THE EVENING...BUT COULD LINGER A LITTLE LONGER ALONG THE TN BORDER BEFORE DISSIPATING OVERNIGHT. LOWS WILL ALSO AGAIN BE ABOVE NORMAL. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 305 AM EDT SUNDAY...NOT A LOT OF CHANGE REGARDING THE SHORT TERM FORECAST PERIOD WHICH INITIALIZES TUESDAY MORNING AMIDST BROAD SUBTROPICAL DEEP LAYER RIDGING. AMPLIFYING UPPER TROF PUSHING THROUGH THE UPPER MISSISSIPPI RIVER VALLEY WILL BE MOVING EAST WITH AN ASSOCIATED COLD FRONT DRAPED ALONG OR JUST NORTH OF THE OHIO RIVER VALLEY. CONTINUED SOUTHERLY FLOW OVER THE SOUTHEAST AHEAD OF APPROACHING FRONTAL BOUNDARY WILL WARRANT NEAR CLIMO POPS FOR MUCH OF THE REGION ON A DIURNAL TREND. ABOVE MENTIONED RIDING WILL PROVIDE SOME INHIBITION TO CONVECTION ON TUESDAY...ESPECIALLY ACROSS THE EAST. WEAK LEE TROF PRESENT ACROSS CENTRAL NC/SC COULD BE A FOCUS FOR CONVECTION PROVIDING ENOUGH LOW LEVEL CONVERGENCE TO SUPPORT INITIATION DESPITE ABOVE MENTIONED CAP. LAPSE RATES ACROSS THE REGION WILL BE RATHER STEEP LATER IN THE DAY AS TEMPS SURGE TO ABOVE NORMAL LEVELS...THEREFORE MODERATE INSTABILITY COULD ALLOW FOR ENHANCED/STRONG CONVECTION ACROSS THE WESTERN MOST ZONES WHERE UPDRAFTS WILL BE LESS INHIBITED. OTHERWISE...EXPECTING GENERAL SHOWERS AND THUNDERSTORMS ON TUESDAY AFTERNOON/EVENING AHEAD OF APPROACHING FRONT. EXPECTING A NOCTURNAL FROPA OVERNIGHT INTO WEDNESDAY MORNING WITH THE MORE ENHANCED UPPER LEVEL SUPPORT PASSING BY TO NORTH. THUS...POPS WILL ACTUALLY TAPER WITH DIURNAL COOLING THROUGH THE NIGHT WITH ONLY LOW END CHANCE LEVEL POPS RESIDING ACROSS THE HIGH TERRAIN. MODELS CONTINUE TO INDICATE THE FRONT SLOWING AND BECOMING NEARLY STATIONARY THROUGH THE REMAINDER OF THE DAY ON WEDNESDAY AS THE UPPER FLOW FLATTENS AND PARENT SURFACE TROF EJECTS TO THE NORTHEAST. THIS WILL BEGIN A RATHER NOCTURNALLY INDUCED UNSETTLED WEATHER PERIOD ACROSS NORTHEAST GA AND THE WESTERN CAROLINAS. DUE TO THE SLOWER/STALLED PROGRESSION OF THE FRONT...EXPECTING ANY SURFACE COOLING/DRYING TO BE MINIMAL. HOWEVER...THE MID AND UPPER LEVELS WILL EXPERIENCE MODERATE DRYING WHICH WILL ACTUALLY ALLOW FOR RATHER STEEP LAPSE RATES WEDNESDAY AFTERNOON. AS THE UPPER RIDGE SLOWLY RETROGRADES WEST AND THE SURFACE HIGH WEAKENS...THE ATMOSPHERE WILL LIKELY BE FREE FOR CONVECTION AMIDST PROFILES SUPPORTING NEARLY 1500J/KG SBCAPE. THUS...POPS WILL RAMP UP INTO THE AFTERNOON TO LOW END LIKELY LEVELS OVER THE MORE CLIMO FAVORED REGIONS OF THE UPPER FRENCH BROAD WHILE SOLID CHANCE POPS RESIDE SOUTH OF INTERSTATE 40 WHERE FRONTAL BOUNDARY REMAINS. WILL CONTINUE TO EVALUATE STRONG/SEVERE THUNDERSTORM POTENTIAL ON WEDNESDAY AS PROFILES WOULD SUPPORT DOWNBURST/HAIL THREATS. TEMPERATURES THROUGH THE SHORT TERM PERIOD WILL REMAIN NEAR OR JUST ABOVE NORMAL. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 330 AM EDT MONDAY...THE EXTENDED RANGE FORECAST PERIOD INITIALIZES THURSDAY MORNING WITH DIFFUSE QUASI STATIONARY MOISTURE AXIS FROM OLD FRONTAL BOUNDARY REMAINING OVER THE REGION. MEANWHILE...UPPER RIDGE WILL REBUILD SOMEWHAT ACROSS THE SOUTHEAST WITH REINFORCING SURFACE HIGH PRESSURE SLIDING EAST AND OUT TO SEA OVER THE MID ATLANTIC. THIS PATTERN WILL PERSIST THROUGH WEEKS END WITH DIURNALLY INDUCED INSTABILITY WORKING TO OVERCOME CAPPING EACH DAY WARRANTING AT LEAST CHANCE LEVEL POPS FOR THE AFTERNOON HOURS. GLOBAL MODELS REMAIN IN CONSENSUS ON ANOTHER RATHER ROBUST FROPA OVER THE WEEKEND WITH SOME DISCONTINUITY REGARDING TIMING AND INTENSITY. THE GFS SOLUTIONS ARE A FEW HOURS FASTER THAN THAT OF THE ECWMF...NEVERTHELESS BOTH INDICATE FRONTAL PASSAGE LATE SATURDAY EVENING INTO SUNDAY. AS THE FRONT APPROACHES...ABOVE MENTIONED SUBSIDENCE WILL WEAKEN AS UPPER HEIGHTS AND SURFACE PRESSURES FALL. THEREFORE FAIRLY HEALTHY POPS ARE FORECAST OVER THE WEEKEND WITH MID LEVEL CHANCE POPS FEATURED ACROSS THE LOWER TERRAIN WHILE NEAR LIKELY LEVEL POPS ARE MENTIONED ACROSS THE NORTHERN MOUNTAINS/FOOTHILLS. HIGH PRESSURE LOOKS TO BUILD IN BEHIND THE FRONT FOR THE START OF THE NEW WORK WEEK LEADING TO DECREASING PRECIPITATION CHANCES AS DRIER AIR ADVECTS IN. TEMPERATURES THROUGH THE MAJORITY OF THE EXTENDED RANGE WILL BE ABOVE NORMAL WITH SLIGHT COOLING FORECAST BEHIND THE LATE WEEKEND FROPA FOR THE NEW WEEK. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... AT KCLT...BKN CIRRUS WILL REMAIN OVER THE AREA THRU THE MORNING WITH SCT HIGH BASED CU DEVELOPING FOR THE AFTERNOON. THE CU WILL BECOME BKN FOR LATE AFTERNOON INTO EARLY EVENING WHEN IT SCATTERS OUT. DO NOT EXPECT ANY VSBY RESTRICTIONS THRU THE PERIOD. LIGHT SW WIND THIS MORNING BECOMES WSW FOR THE AFTERNOON. LIGHT SLY WIND EXPECTED DURING THE EVENING AND OVERNIGHT. BEST CHC OF CONVECTION WILL BE ACROSS THE MTNS. ELSEWHERE...OUTSIDE OF THE MTNS WILL SEE SIMILAR CONDITIONS AS KCLT. KAVL WILL SEE VLIFR THRU 13Z...LIFR BECOMING LOW VFR BY 14Z. THERE WILL ALSO BE SOME SHRA AROUND THIS MORNING. NWLY WIND PICKS UP THIS MORNING BECOMING SLY THIS AFTERNOON...THEN CALM OVERNIGHT. SHUD BE ANOTHER NITE WITH AT LEAST IFR AND LIKELY VLIFR BEFORE DAYBREAK. KAVL HAS THE BEST CHC OF SEEING ANY AFTERNOON/EVENING CONVECTION. HOWEVER...CHC STILL TOO LOW TO INCLUDE IN THE TAF ATTM. OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE WEEK...BUT RESTRICTIONS ARE POSSIBLE EARLY EACH MORNING DUE TO LOW CLOUDS AND FOG...PRIMARILY IN THE MOUNTAIN VALLEYS. DIURNALLY DRIVEN SHRA/TSRA ARE EXPECTED EACH AFTERNOON WITH THE MOST COVERAGE OVER THE MOUNTAINS. CONFIDENCE TABLE... 10-16Z 16-22Z 22-04Z 04-10Z KCLT HIGH 94% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 91% HIGH 100% HIGH 100% HIGH 100% KAVL MED 71% HIGH 100% HIGH 100% HIGH 81% KHKY HIGH 94% HIGH 100% HIGH 100% HIGH 100% KGMU HIGH 91% HIGH 100% HIGH 100% HIGH 100% KAND HIGH 94% 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...CDG NEAR TERM...RWH SHORT TERM...CDG LONG TERM...CDG AVIATION...RWH

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