Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 230228 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1028 PM EDT MON SEP 22 2014 .SYNOPSIS... COOL AND DRY HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH MID WEEK. MOISTURE AND RAIN CHANCES INCREASE AS WE GO INTO THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/... AS OF 1020 PM...LATEST IR LOOP INDICATED AN EXPANDING AREA OF COLD CLOUD TOPS ACROSS THE CENTRAL AND EASTERN CAROLINAS. THE INCREASING CLOUD COVER IS DEVELOPING EAST OF THE CENTER OF A NEWLY FORMED MID LEVEL LOW. THE GREATEST MOISTURE AND FORCING SHOULD REMAIN EAST OF THE REGION. I WILL KEEP THE FORECAST DRY TONIGHT. LOW TEMPERATURES ARE FORECAST FROM THE 40S ACROSS THE MTNS TO MID 50S EAST. AS OF 745 PM...LATEST W/V LOOP SHOWS A MID LEVEL TROF AMPLIFYING ACROSS THE SOUTHERN APPALACHIAN REGION. MODELS INDICATE THAT A CLOSED LOW WILL DEVELOP THIS EVENING AND WILL REMAIN THROUGH TONIGHT AND TOMORROW. AS A RESULT...MODELS INDICATE THAT PIEDMONT WILL REMAIN UNDER CLOUD COVER ASSOCIATED WITH A DEVELOPING COASTAL SYSTEM. I WILL UPDATE THE FORECAST TO ADJUST SKY AND WIND. AS OF 230 PM EDT MON...THIS AFTERNOON AND EVENING...AREAS OF SHOWERS AND THUNDERSTORMS WERE KEEP DEVELOPING ALONG AND IN THE VICINITY OF THE SURFACE BOUNDARY TO OUR SOUTH AS OF THIS AFTERNOON. A DEEP MOISTURE AXIS JUST TO OUR SOUTH WILL CONTINUE TO BRING CONSIDERABLE LOW-MID LEVEL CLOUDINESS TO THE SOUTHERN HALF OF THE CWA THROUGH THIS EVENING. CONDITIONS SHOULD REMAIN MOSTLY DRY FOR MOST LOCATIONS AS A CANADIAN HIGH PRESSURE CONTINUES TO BUILD IN FROM THE N/NE. THE EXCEPTION WILL BE OVER THE EXTREME SOUTHERN ZONES OF THE FORECAST AREA WHERE SLIGHT TO LOW END CHANCES FOR SHOWERS WERE WARRANTED AT LEAST THRU LATE THIS AFTERNOON. TONIGHT AND TOMORROW...LATEST NEAR TERM MODELS CONTINUE TO INDICATE THAT A POTENT UPPER SHORTWAVE ENERGY WILL ROUND THE BASE OF THE EASTERN CONUS TROUGH...CLOSING OFF AS AN UPPER LOW AS IT MOVES ACROSS THE REGION TONIGHT. THIS UPPER FEATURE IS EXPECTED TO SLOWLY PULL NE AWAY FROM THE REGION TOMORROW. DESPITE THIS UPPER FEATURE...CONDITIONS SHOULD REMAIN DRY AS A COOL CANADIAN HIGH PRESSURE BUILDS IN FROM THE NE AND THE BEST UPPER FORCING REMAINS SOUTH AND EAST OF THE CWA. WITH STRONG CAA IN N/NE FLOW (H85 TEMPS OF 10C-12C WILL PUSH SOUTH INTO THE UPSTATE SC) TEMPS...OVERNIGHT LOWS WILL PLUNGE TO THE UPPER 30S/LOW 40S OVER THE HIGHER TERRAIN AND 50S OVER THE PIEDMONT. AFTERNOON HIGHS FOR TOMORROW WILL REMAIN 5-10 DEGREES BELOW NORMAL GIVEN PERSISTENT COOL NE WINDS. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... A CLOSED UPPER LOW OVER THE SE U.S. WILL GRADUALLY FILL THROUGH THE SHORT TERM LEAVING A WEAK UPPER TROUGH OVER THE AREA BY THU. AT THE SURFACE...HIGH PRESSURE INTIALLY OVER NEW ENGLAND WILL BE DISPLACED INITIALLY TO THE EAST BY A WEAK LOW MOVING NORTHWARD FROM OFF THE CAROLINA COAST. BY THU...THE HIGH IS FORECAST TO RE-DEVELOP TO THE WEST OVER THE EASTERN GREAT LAKES AND RIDGE SOUTHWARD AGAIN ALONG THE EAST SLOPES OF THE APPALACHIANS. THE NET RESULT INITIALLY WILL BE AN INCREASE IN DEEP LAYER MOISTURE ACROSS THE THE WESTERN CAROLINAS AND NE GA ON WED INTO WED NIGHT THANKS TO SOME ISENTROPIC UPGLIDE AS THE COASTAL LOW DEVELOPS TO THE EAST. HENCE...CLOUD COVER WILL INCREASE DURING WED. AS WE GET INTO WED NIGHT...THE MODELS SHOW SOME LIGHT QPF RESPONSE MAINLY EAST OF I-26. HENCE..WILL BUMP POPS UPWARD INTO THE CHANCE CATEGORY ANTICIPATING SOME PATCHY LIGHT SHOWERS. THE SHOWERS SHOULD TEND TO WANE ON THU AS THE COASTAL LOW MOVES NE. HOWEVER...MODEL TIME-HEIGHTS INDICATE THAT CLOUD COVER WILL BE SLOW TO DISSIPATE. TEMPS WILL REMAIN BELOW CLIMO THROUGH THE PERIOD. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... AS OF 2 PM MONDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON FRIDAY WITH BROAD AND STEEP UPPER RIDGING PERSISTING ACROSS MOST OF THE CONUS. THE RIDGE IS EXPECTED TO BEGIN BREAKING DOWN OVER THE WEEKEND AS SOME SORT OF COMPLEX...SPLIT UPPER FLOW PATTERN DEVELOPS OVER THE CENTRAL CONUS. BECAUSE THE POLAR JET WILL LIKELY REMAIN WELL TO THE NORTH...THE UPPER FLOW WILL REMAIN WEAK OVER MUCH OF THE CENTRAL AND EASTERN CONUS. THIS MAKES IT DIFFICULT TO PREDICT EXACTLY HOW THE UPPER PATTERN WILL EVOLVE AS THE RIDGE BREAKS DOWN ON DAYS 6 AND 7. THE OLDER 00Z RUN OF THE ECMWF CLOSES OFF AN H5 LOW OVER ARKANSAS BY EARLY MON AND MOVES THAT LOW TO OUR DOORSTEP BY EARLY TUES. THE NEWER 12Z GFS JUST MAINTAINS SOME DEGREE OF UPPER SWV ENERGY OVER THE SAME REGION AND DOES NOT FORM A CLOSED LOW. AT THE SFC...HIGH PRESSURE WILL BE CENTERED TO OUR NORTH WITH COOL NELY LOW LVL FLOW OVER THE FCST AREA. OVER THE NEXT FEW DAYS THE LATEST GUIDANCE KEEPS THE HIGH NEARLY STATIONARY...EXCEPT FOR THE ECMWF...WHICH MOVES IT SLIGHTLY WESTWARD. THE ECMWF STILL REMAINS MORE BULLISH WRT DEEPER LYR MOISTURE PERSISTING OVER THE CWFA FROM THE SOUTH AND EAST ON FRI AND SAT WHILE THE LATEST 12Z GFS...AND CMC...CONTINUE TO KEEP THE HIGHER RH VALUES JUST TO OUR SOUTH THRU AT LEAST SAT. BY SUN...THE MODELS TRY TO SPIN UP SOME SORT OF GULF OF MEXICO LOW WHICH SPREADS DEEPER MOISTURE OVER MOST OF THE CWFA BY LATE SUN. MON APPEARS TO HAVE THE BEST CHANCE FOR ANY WIDESPREAD PRECIP WITH DEEPER MOISTURE OVER MOST OF THE REGION AND SOME DEGREE OF UPPER LVL SUPPORT JUST TO OUR WEST. AS FOR THE SENSIBLE FCST...I KEPT POPS AT JUST A SLIGHT CHANCE OR BELOW ON FRI AND SAT WITH VALUES INCREASING TO SOLID CHANCE OVER THE MOST OF THE CWFA BY LATE SUN AND HIGHER END SOLID CHANCE BY MON AFTERNOON. TEMPS WERE LARGELY UNCHANGED FROM THE PREVIOUS FCST WITH THE COOLEST VALUES EXPECTED AT THE BEGINNING OF THE PERIOD ON FRI WITH SOME MINOR WARMING GOING INTO THE WEEKEND. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... AT KCLT...LATEST W/V LOOP SHOWS A MID LEVEL TROF AMPLIFYING ACROSS THE SOUTHERN APPALACHIAN REGION. MODELS INDICATE THAT A CLOSED LOW WILL DEVELOP THIS EVENING AND WILL REMAIN THROUGH THE TAF PERIOD. AS A RESULT...MODELS INDICATE THAT CLT WILL REMAIN UNDER CLOUD COVER ASSOCIATED WITH A DEVELOPING COASTAL SYSTEM. FOR THE 0Z TAF...CLOUD BASES ARE FORECAST TO RANGE ABOVE RESTRICTIVE LEVELS. TRENDS WILL BE MONITORED FOR DEVELOPING LOWER CLOUDS OR POSSIBLE RAIN. OTHERWISE...THE TAF WILL FEATURE STEADY NORTHEAST WINDS...DIRECTIONS RANGING FROM 030-050 DEGREES...MARGINALLY GUSTY DURING THE DAYLIGHT HOURS TUESDAY. ELSEWHERE...CONDITIONS SIMILAR TO CLT. KAVL MAY SEE PERIODS OF RESTRICTIVE UPSLOPE CLOUDS AROUND DAYBREAK TUES...I WILL TEMPO BKN009 BETWEEN 10-14Z. KAVL WILL MAINTAIN NNW WIND THROUGH THE TAF PERIOD. OUTLOOK...DRY HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH THE WEEK...WITH EASTERLY FLOW MOISTURE POSSIBLY RETURNING FROM THE COAST THIS WEEKEND. CONFIDENCE TABLE... 02-08Z 08-14Z 14-20Z 20-02Z 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...JOH/NED SHORT TERM...LG LONG TERM...JPT AVIATION...NED

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