Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 300515 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 115 AM EDT TUE JUN 30 2015 .SYNOPSIS... THE NEXT COUPLE OF DAYS WILL FEATURE A WARMING AND MOISTENING TREND BEFORE A FRONTAL BOUNDARY APPROACHES BY THE MIDDLE OF THE WEEK...DRIVING RAIN AND THUNDERSTORM CHANCES UP. AND UNSETTLED WEATHER PATTERN WILL PERSIST THROUGH THE WEEKEND...WITH TYPICAL SUMMERTIME AFTERNOON SHOWERS AND THUNDERSTORMS DEVELOPING EACH DAY AND HIGH TEMPERATURES WARMING TO NEAR NORMAL BY NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... 0515 UTC UPDATE...WINDS WERE UPDATED WITH A BLEND OF THE LATEST NAM AND ADJMAV...FAVORING GUSTS DURING DAYLIGHT HOURS. POPS AND QPF WERE UPDATED BASED ON ACTIVITY MOVING ACROSS THE NORTHERN NC MOUNTAINS. AS OF 1030 PM EDT MONDAY...CONVECTION TO THE WEST OVER THE CUMBERLAND PLATEAU INTO THE GREAT TN VALLEY IS FCST TO CONTINUE MARCHING EASTWARD OVER THE NEXT FEW HOURS. AS SUCH...LATEST CAM GUID ONCE AGAIN FAVORS THE SOUTHERN TIER OF THE ONGOING CONVECTION WITH THE NORTHERN ACTIVITY FALLING OFF ONCE IT ENCOUNTERS THE TERRAIN...AND A MORE STABLE ENVIRONMENT. FURTHER SOUTH THE MOST RECENT MESOANALYSIS DOES INDICATE BETTER MUCAPE...MAINLY OVER THE SMOKIES. THUS...CANT RULE OUT SOME UPSTREAM CONVECTION MOVING INTO SW NC BEFORE IT ENCOUNTERS MORE STABILITY AND WAINS. FOR THE FCST...TWEAKED POPS A BIT TO BETTER REFLECT LATEST GUID HOWEVER NO SIG CHANGES WERE MADE. OTHERWISE...MADE SLIGHT ADJUSTMENTS TO TEMPS/DEWS/SKY AND LEFT THE REMAINDER OF THE FCST AS IT WAS. PREVIOUS DISCUSSION... AS OF 225 PM...LATEST SATELLITE IMAGE INDICATED A BAND OF DEBRIS CLOUDS ACROSS THE NC MTNS...WITH A SHALLOW CU FIELD ACROSS THE NC AND NRN SC FOOTHILLS AND PIEDMONT. A FEW SHRA TO ISO TSRA MAY REACH THE TN BORDER COUNTIES OF NC BEFORE DISSIPATING THIS EVENING. AT 2 PM...A LIGHT CLUSTER OF SHRA WAS LOCATED NEAR THE INTERSECTION OF GA/AL/TN STATE LINES. AT 2 PM...SPC CAPE ANALYSIS INDICATED 100 TO 200 J/KG ACROSS THE EXTREME WESTERN NC MTNS...WHICH AGREES QUITE WELL WITH THE 12Z NAM. I EXPECT THAT UPSTREAM CONVECTION WILL SURVIVE TO REACH THE TN BORDER...ALONG WITH A FEW SHRA/TSRA DEVELOPING OVER THE NC RIDGES...I WILL HIGHLIGHT WITH CHC TO SCHC POPS AFTER 20Z. SHRA/TSRA MAY TRACK SLOWLY EAST...BUT SHOULD DISSIPATE BEFORE REACHING THE FOOTHILLS. THE REST OF THE NIGHT...A FEW SHRA MAY CONTINUE TO BRUSH THE TN LINE...I WILL INDICATE SCHC POPS. PARTLY TO MOSTLY CLOUDY SKY WITH LIGHT SW WINDS SHOULD RESULT IN MIN TEMPERATURES TO RANGE WITHIN A DEGREE OR TWO OF NORMAL. ON TUESDAY...IT APPEARS THAT THE REGION WILL RETURN TO SUMMER-LIKE CONDITIONS. CONTINUED RETURN FLOW SHOULD RESULT IN DEWPOINTS TO RANGE IN THE LOW TO MID 60S DURING THE AFTERNOON. USING A BLEND OF GUIDANCE...HIGH TEMPERATURES ARE FORECAST TO RANGE FROM THE LOW 80S WITHIN THE NC MTN VALLEYS TO AROUND 90 EAST. FORECAST SOUNDINGS INDICATE THAT CAPE VALUES SHOULD RANGE FROM 1000 TO 2000 J/KG ACROSS THE REGION...WITH LITTLE TO NO CIN. THE NEAR TERM MODELS INDICATE THAT A MID LEVEL S/W WILL RIPPLE ACROSS THE SOUTHERN APPALACHIANS DURING THE AFTERNOON. AS THE S/W APPROACHES...DEEP CONVECTION IS FORECAST TO DEVELOP ACROSS THE MTNS BY MID DAY. COVERAGE ACROSS FOOTHILLS AND PIEDMONT SHOULD INCREASE DURING THE AFTERNOON. STEERING FLOW MAY YIELD EAST BOUND STORMS AROUND 15 M/S. I WILL FORECAST HIGH CHC TO LIKELY POPS ACROSS THE MTNS...WITH SOLID CHC POPS EAST. SPC DY2 HIGHLIGHTS MOST OF THE SOUTHEAST U.S. WITH A MARGINAL RISK...5 PERCENT CHC FOR SEVERE STORMS. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... AS OF 2 PM MONDAY...SOME SEMBLANCE OF THE EAST COAST TROUGH WILL PERSIST INTO LATE WEEK. HOWEVER...SOME WEAKENING IN THE PATTERN IS FORECAST BY LATE THU AS AN UPPER LOW DEVELOPS IN EASTERN CANADA WITH AN ENSUING SPLIT FLOW REGIME TO THE SOUTH. DURING THIS TIME...A SERIES OF LOW PRESSURE SYSTEMS WILL MOVE THROUGH THE OHIO VALLEY ALONG A QUASI-STATIONARY BOUNDARY. ALOFT A SERIES OF WEAK SHORT WAVES ROTATING THROUGH THE UPPER TROUGH HAVE THE POTENTIAL TO ENHANCE CONVECTION...ESPECIALLY IF THEY ARRIVE DURING THE OPTIMUM DIURNAL CYCLE TIME. IN REGARD TO THE SENSIBLE WEATHER IN THE SOUTHERN APPALACHIANS AND THE WESTERN CAROLINAS...IT LOOKS LIKE THE PERIOD CAN CERTAINLY BE CHARACTERIZED AS UNSETTLED. MODEL TIME HEIGHTS SHOW RATHER DEEP LAYER MOISTURE WITH PWATS INCREASING TO NEAR 2 INCHES BY THURSDAY. ALSO...THERE CERTAINLY ARE SOME DISAGREEMENTS IN THE MODEL DETAILS. THE 12Z NAM IS A LITTLE FARTHER SOUTH WITH THE STORM TRACK AND BRINGS THE LOWS THROUGH THE CENTRAL APPALACHIANS. THIS RESULTS IN THE MODEL BRINGING WHAT LOOKS LIKE A MCS INTO THE NC MOUNTAINS BY LATE WED WHICH PUSHES ACROSS THE MOUNTAINS WED NIGHT WITH AREAS OF VERY GENEROUS QPF. THE GFS IS MUCH MORE MUTED WITH NOT NEARLY THE QPF AS THE NAM. THE NAM APPEARS TO BE AN OUTLIER IN COMPARISON ALSO WITH THE EC AND SREF...SO WILL LEAN TOWEARD THE GFS SOLUTION. THIS WILL RESULT IN DIURNALLY ENHANCED SCT THUNDERSTORMS ON WED AFTERNOON AND EVENING. WITH WIND FIELDS REMAINING STRONGER THAN USUAL FOR EARLY JULY AND CAPES INCREASING TO >1000J...SOME SCT SEVERE STORMS ARE OUT OF THE QUESTION. IT IS LOOKING LIKE THU COULD BE THE MORE ACTIVE DAY IN REGARD TO OVERALL COVERAGE OF THUNDERSTORMS AS A SHORT WAVE ROTATES THROUGH DURING THE AFTERNOON. WILL THEREFORE INCREASE POPS TO NUMEROUS OVER A LARGE PORTION OF THE FORECAST AREA ON THURSDAY AFTERNOON. TEMPS ARE FORECAST TO BE NEAR CLIMO EACH DAY...EXCEPT A COUPLE DEGREES BELOW ON THU WESTERN PORTIONS DUE TO MORE CLOUDS/PRECIP. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... AS OF 230 PM MONDAY...THE MEDIUM RANGE BEGINS THURSDAY NIGHT AS A WEAK SURFACE LOW/VORT MAX ROUNDS THE BASE OF THE LONGWAVE H5 TROUGH TOWARDS THE SPINE OF THE SOUTHERN APPALACHIANS. THIS WILL KEEP POPS ELEVATED EVEN INTO THE OVERNIGHT HOURS HEADING INTO FRIDAY MORNING. OVERALL HEIGHTS BEGIN TO RISE AS THE UPPER TROUGH BREAKS DOWN ON FRIDAY...THOUGH A BOUNDARY IN CLOSE PROXIMITY TO THE FORECAST AREA AND PLENTIFUL SOUTHERN STREAM MOISTURE WILL KEEP POPS ELEVATED WELL ABOVE CLIMO TO END THE WORK WEEK. THE AXIS OF ANOTHER H5 TROUGH AND AN ASSOCIATED SPOKE OF VORTICITY WILL ARRIVE JUST IN TIME FOR PEAK HEATING ON SATURDAY...WITH ACCOMPANYING POPS NEAR OR JUST ABOVE NORMAL...THOUGH CONVECTION APPEARS TO FOLLOW A TYPICAL TREND OF WANING SOMEWHAT AFTER SUNSET. THE TROUGH IS PROGRESSIVE IN LIFTING OFF THE NORTHEAST CONUS LATE IN THE WEEKEND...LEAVING A NORMAL JULY DIURNAL PATTERN OF POPS FOR EARLY NEXT WEEK. MAX TEMPS FOR THE MEDIUM RANGE WILL START NEAR AVERAGE AT THE END OF THIS WEEK...THEN RISE TO JUST ABOVE CLIMO THIS WEEKEND AND THROUGH NEXT WEEK. A TYPICAL MOIST SUMMERTIME AIRMASS WILL LIMIT THE DIURNAL TEMPERATURE RANGE...KEEPING MIN TEMPS SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... AT KCLT...VFR. GUIDANCE BRINGS A LOW VFR CIG OVER THE AREA AROUND MIDDAY AS THE REMAINS OF A COLD FRONT MOVE IN FROM THE WEST. WINDS WILL FAVOR THE SW...BECOMING GUSTY DURING THE DAY. CONVECTIVE CHANCES RAMP UP ENOUGH TO WARRANT A MENTION IN THE TAF THIS AFTERNOON AND EVENING. GUIDANCE IS NOT SUPPORTIVE OF A DAYBREAK FOG RESTRICTION. ELSEWHERE...VFR. THE BULK OF OVERNIGHT CONVECTIVE ACTIVITY IS EXPECTED TO REMAIN N OF KAVL...AND WILL LOSE STEAM ANYWAY AS IT ENCOUNTERS A MORE STABLE ATMOSPHERE. ALTHOUGH SEVERAL GUIDANCE MEMBER FAVOR A DAYBREAK FOG RESTRICTION AT KAVL...THE CONSENSUS DOES NOT. LOW VFR CIGS WILL OVERSPREAD THE REGION AROUND MIDDAY AHEAD OF AN APPROACHING SURFACE BOUNDARY. CONVECTION ASSOCIATED WITH THIS BOUNDARY WILL BE OF GREAT ENOUGH COVERAGE FOR A LATE AFTERNOON AND EARLY EVENING MENTION IN THE TAFS. WINDS WILL FAVOR THE SW...WITH DAYTIME GUSTS...EXCEPT AT KAVL WHERE WINDS MAY OCCASIONALLY CHANNEL UPVALLEY FROM THE NW. OUTLOOK...A LINGERING BERMUDA HIGH COMBINED WITH AN AMPLIFYING LONGWAVE TROF OVER THE SOUTHEAST WILL GRADUALLY INCREASE MOISTURE AND INSTABILITY THROUGH MOST OF THE WORK WEEK. THUNDERSTORM COVERAGE MAY INCREASE EACH DAY THROUGH WEDNESDAY...WITH SCT TO NUM DIURNAL THUNDERSTORMS LATE IN THE WEEK. RESTRICTIONS MAY OCCUR WITH PASSING STORMS...AND EACH MORNING OVER AREAS OF WET SOIL. CONFIDENCE TABLE... 05-11Z 11-17Z 17-23Z 23-00Z KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL HIGH 100% HIGH 83% 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...LEV NEAR TERM...CDG/JAT/NED SHORT TERM...LG LONG TERM...LEV AVIATION...JAT

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