Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 301736 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 136 PM EDT THU JUL 30 2015 .SYNOPSIS... A COLD FRONT WILL MOVE INTO THE REGION FROM THE NORTHWEST TODAY AND SETTLE SOUTHEAST OF THE AREA TONIGHT THROUGH FRIDAY. THE FRONT AND ASSOCIATED DEEPER MOISTURE WILL LIKELY REMAIN CONFINED ALONG THE SOUTHEAST COASTLINE THROUGH THE WEEKEND...WITH SLIGHTLY COOLER TEMPERATURES AND MUCH DRIER AIR EXPECTED OVER THE FORECAST AREA. LOW LEVEL MOISTURE WILL GRADUALLY RETURN EARLY NEXT WEEK AS ANOTHER COLD FRONT APPROACHES FROM THE NORTH. && .NEAR TERM /THROUGH TONIGHT/... AS OF 130 PM...ISOLATED TO WIDELY SCATTERED CONVECTION HAS BEGUN TO DEVELOP ACRS THE CWFA...IN LINE WITH THE CURRENT POP TRENDS. TEMPS AND DEWPTS ARE ALSO ON TRACK. SO NO SIGNIFICANT CHANGES WITH THIS UPDATE. AS OF 1015 AM...THE 12Z SFC ANALYSIS SHOWED THE COLD FRONT PUSHING INTO THE SMOKIES AND GREAT TENN VALLEY. THE FRONT WILL CONTINUE TO PUSH ACRS THE MTNS THRU MIDDAY...THEN ACRS THE PIEDMONT THIS AFTN. THERE IS LESS CLOUD COVER AT THIS TIME OF DAY THAN THE LAST FEW DAYS. SO TEMPS ARE WARMING QUICKLY...DESPITE HUMID BL...WITH DEWPTS STILL IN THE LWR-MID 70S. THIS IS RESULTING IN SBCAPE ALREADY IN THE 1500-2500 J/KG RANGE ON THE SPC MESOANALYSIS PAGE ACRS THE PIEDMONT. I HAVE BUMPED MAX TEMPS UP A DEG OR TWO GIVEN THE TRENDS. AS FOR POPS...ONE WOULD EXPECT DECENT COVERAGE OF SHWRS AND TSTMS...GIVEN DECENT INSTBY AND A BOUNDARY WORKING THRU THE AREA. HOWEVER...THE LATEST CAMS ARE A BIT MUTED. I TRIED BLENDING IN CAM POP...BUT THAT DROPPED POP DOWN ACRS MUCH OF THE AREA. SO I PRETTY MUCH KEPT POPS AS IS...WHICH IS IN THE 30-40 PCT RANGE. SEVERE THREAT IS STILL MARGINAL...WITH WIND BEING THE MAIN THREAT. AS OF 650 AM...THE FORECAST APPEARS IN GOOD SHAPE. I WILL TAYLOR POPS TO REFLECT LIGHT RETURNS OVER THE WESTERN NC MTNS. IN ADDITION...I WILL REDUCE FOG MENTION. AS OF 345 AM...LATEST SFC ANALYSIS INDICATED THAT A COLD FRONT WAS CROSSING MIDDLE KY AND TN...MOVING EAST. BASED ON RECENT OBSERVATION TRENDS AND MODEL GUIDANCE...THE COLD FRONT IS EXPECTED TO SWEEP ACROSS THE SOUTHERN APPALACHIANS AROUND MID DAY...REACHING THE PIEDMONT LATE THIS AFTERNOON/EARLY EVENING. MOS GUIDANCE INDICATES THAT HIGH TEMPERATURES SHOULD RANGE IN THE MID 80S WITHIN THE MTN VALLEYS TO LOW TO MID 90S EAST. SFC DEWPOINTS ARE FORECAST TO REMAIN BETWEEN 66 TO 71 DEGREES DURING THE HEAT OF THE AFTERNOON. MODEL SOUNDINGS AND PLAIN VIEW SHOW CAPES GENERALLY RANGING NEAR 2000 J/KG. NAM AND RAP DCAPE INCREASE TO VALUES GREATER THAN 1000 J/KG ALONG AND AHEAD OF THE FRONT. BASED ON THE NAM...A BROKEN BAND OF TSRA SHOULD DEVELOP ALONG AND AHEAD OF THE FRONT. THE CONVECTION MAY CROSS THE MTNS DURING THE MORNING DAYLIGHT HOURS...SLIDING ACROSS THE PIEDMONT DURING THE EARLY TO MID AFTERNOON. IN THE WAKE OF THE BAND...SCT DISCRETE CELLS MAY DEVELOP...MOVING EAST BY SUNSET. GIVEN THE MODERATE CAPE...A WIDE FIELD OF DCAPE...AND THE DAYTIME PASSAGE OF A COLD FRONT...IT APPEARS THAT SEVERAL STORMS COULD PRODUCE DAMAGING WIND GUSTS. HAIL IS POSSIBLE...BUT HIGH WBZ SHOULD LIMIT HAIL SIZE TO LESS THAN SEVERE. WE WILL HIGHLIGHT THE SEVERE POTENTIAL IN THE HWO. TONIGHT...WEAK CAA AND FALLING DEWPOINTS WILL INCREASE FROM NW TO SE IN THE WAKE OF THE FRONT. SKY COVER SHOULD CLEAR FROM WEST TO EAST...WITH MOST OF THE AREA UNDER LITTLE CLOUD COVER BY DAWN FRIDAY. GIVEN THE LIGHT NNW WINDS...THE COOLEST THICKNESSES SHOULD REMAIN OVER THE MTNS. I WILL FORECAST LOWS IN THE 50S AND 60S ACROSS THE MTNS...WITH LOW 70S EAST. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... AS OF 330 AM EDT THURSDAY...A BROAD EASTERN TROUGH WILL DEVELOP ON FRIDAY. UNDER THIS TROUGH...DRIER AIR WILL SPILL INTO THE REGION FROM THE NORTH AS A DEPARTING SFC FRONT SETTLES TO THE SOUTHEAST COAST AND SURFACE HIGH PRESSURE STRETCHES FROM THE MID MS RIVER VALLEY TO THE SRN AND CENTRAL APPALACHIANS. DEWPOINTS ADVECTING/MIXING WELL DOWN IN THE 50S IN MOST AREAS WILL LARGELY PRECLUDE ANY CONVECTION ON FRIDAY...WITH ANY ISOLD SHOWERS CONFINED TO THE EXTREME LOWER PIEDMONT DURING THE AFTERNOON HOURS. THE EASTERN TROUGH WILL AMPLIFY OVER THE WEEKEND AS A SERIES OF SHORTWAVES MOVE THROUGH THE MEAN TROUGH AXIS. DRY SFC HIGH PRESSURE WILL REMAIN IN PLACE ON SATURDAY...WITH A WEAKLY REINFORCING SURFACE FRONT APPROACHING FROM THE NORTH LATE IN THE DAY. ISOLATED SHOWER OR WEAK TSTM COVERAGE MAY OCCUR LATE DAY JUST N OF THE REGION ALONG THE FRONT AND ALSO ACROSS THE SOUTHERN TIER WHERE DEWPOINTS MAY RECOVER EVER SO SLIGHTLY. THE AIRMASS WILL CONTINUE TO MODIFY ON SUNDAY...BUT WITH MOISTURE VERY SLOW TO RETURN. THE SHORTWAVES MOVING THROUGH THE ERN TROUGH WILL REMAIN DIFFICULT TO TIME...BUT THERE IS DEVELOPING CONSENSUS ON STRONGER Q VECTOR CONVERGENCE WITH A SHORTWAVE LATE SUNDAY INTO SUNDAY NIGHT JUST AS MOISTURE REBOUNDS SLIGHTLY. THIS WILL WARRANT BETTER ISOLD COVERAGE OF SHRA/TSRA LATE SUNDAY...WITH MORE OF A NON DIURNAL ISOLD NIGHTTIME POP MENTION ON SUNDAY NIGHT. TEMPERATURES WILL REMAIN NEAR TO SLIGHTLY ABOVE CLIMO THROUGH THE PERIOD. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 330 AM EDT THURSDAY...MODEL CONSENSUS DEPICTS SLIGHT SHALLOWING OF THE ERN TROUGH MONDAY THROUGH WEDNESDAY. MEANWHILE... A MORE VIGOROUS SURFACE COLD FRONT WILL MOVE SOUTH OF THE GREAT LAKES ON MONDAY AND APPROACH THE FORECAST AREA FROM THE NORTH ON TUESDAY. THERE IS CONSIDERABLE MEDIUM RANGE MODEL SPREAD ON HOW FAR SOUTH THE FRONT GETS...WITH THE ECMWF GENERALLY STALLING THE BOUNDARY N OF THE AREA...WHILE THE GFS AND ASSOCIATED ENSEMBLES BRING IT AT LEAST INTO THE NRN TIER BEFORE TURNING IT AROUND AS A WARM FRONT ON WEDNESDAY. A CONSENSUS APPROACH WILL KEEP THE BOUNDARY N OF THE AREA BUT FEATURE AN UPTICK IN DIURNAL AFTN CONVECTIVE COVERAGE AHEAD OF THE FRONT AS THE BOUNDARY LAYER CONTINUES TO REBOUND AND LAPSE RATES FURTHER STEEPEN ALOFT. TEMPERATURES WILL GRADUALLY WARM THROUGH THE PERIOD. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AT KCLT...A RATHER WEAK AND NEBULOUS COLD FRONT WILL CROSS THE KCLT AREA THIS EVENING. IT IS HELPING TO INITIATE CONVECTION ACRS THE BLUE AND NC FOOTHILLS N OF KCLT...AND THAT ACTIVITY WILL DRIFT SOUTH ACRS THE AREA BETWEEN 19-22Z. GUIDANCE HAS SOME ISOLATED CONVECTION DEVELOPING ALONG THE TRAILING FRONT AFTER 00Z THIS EVENING ACRS THE NC PIEDMONT. CONFIDENCE IS LOW ON THIS...AS DRY AIR WILL BEGIN TO FILTER IN AND THE BL WILL BE STABILIZING. SO WILL NOT MENTION ANY PRECIP BEYOND THE TEMPO. OVERNIGHT...THERE IS BETTER AGREEMENT ON LINGERING VFR STRATOCU WELL INTO THE NIGHT...AS MOISTURE LINGERS BELOW A DEVELOPING INVERSION AROUND 5000-7000 FT AGL. DRY AIR WILL EVENTUALLY CLEAR THIS OUT FRIDAY MORNING. WINDS ARE ALREADY FAVORING A N DIRECTION AHEAD OF THE FRONT...AND WILL CONTINUE TO THRU THE PERIOD...INCREASING BEHIND THE FRONT TO AROUND 8-10 KTS BEFORE DAYBREAK FRIDAY. ELSEWHERE...SCATTERED CONVECTION THIS AFTN SEEMS TO WARRANT VCTS FOR ALL SITES. CLOUD BASES WILL HOVER AROUND 4500-6000 FT...THEN LIFT TO AROUND 7000-8000 FT BEHIND A PASSING COLD FRONT THIS EVENING. THE NAM HAS POTENTIAL MVFR CIGS AT KAVL FOR A BRIEF TIME THIS EVENING...SO WILL MENTION SCT FOR NOW. A N WIND WILL INCREASE SLIGHTLY OVERNIGHT...WITH DRY AIR WORKING IN. SO NOT EXPECTING ANY FOG OR LOW CLOUDS OUTSIDE THE LITTLE TN RIVER VALLEY. THE VFR-LVL STRATOCU IS EXPECTED TO DISSIPATE FRIDAY MORNING. OUTLOOK...DRY HIGH PRESSURE WITH BUILD IN ACRS THE REGION FRIDAY...ALLOWING FOR GENERALLY DRY AND QUIET WEATHER THROUGH THE WEEKEND. A GRADUAL INCREASE IN CHANCES FOR SHOWERS/THUNDERSTORMS AND RESTRICTIONS WILL RETURN FOR THE START OF THE NEW WORK WEEK. CONFIDENCE TABLE... 17-23Z 23-05Z 05-11Z 11-12Z KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL HIGH 100% HIGH 100% LOW 56% 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...HG NEAR TERM...ARK/NED SHORT TERM...HG LONG TERM...HG AVIATION...ARK

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