Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 171058 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 658 AM EDT THU APR 17 2014 .SYNOPSIS... AN UNSEASONABLY COLD AIR MASS WILL REMAIN OVER THE REGION INTO FRIDAY. A SUBTROPICAL LOW WITH DEEP MOISTURE WILL DEVELOP ACROSS THE SOUTHEAST STATES ON FRIDAY AND SATURDAY. BY EARLY NEXT WEEK...TEMPERATURES SHOULD RANGE CLOSE TO NORMAL AHEAD OF AN APPROACHING COLD FRONT. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 645 AM...CIRRUS HAS OVERSPREAD THE AREA AND WILL REMAIN THRU THE DAY. GUIDANCE IS NOW IN GOOD AGREEMENT SHOWING LOW CLOUDS MOVING INTO THE AREA FROM THE SOUTH THIS EVENING AND OVERNIGHT. SAT PIX SHOW THESE CLOUDS ALONG THE GA/SC COAST WITH A NORTHWARD TRAJECTORY. OTHERWISE...GOING FCST LOOKS ON TRACK...SO UPDATES MAINLY FOR CURRENT CONDITIONS. AS OF 245 AM...HIGH PRESSURE REMAINS RIDGED INTO THE AREA FROM THE NE TODAY. RISING THICKNESSES...SUN FILTERING THRU MOSTLY THIN CIRRUS AND A MODERATING AIR MASS WILL LEAD TO WARMER HIGHS TODAY. HOWEVER...THEY WILL STILL BE AROUND 10 DEGREES BELOW NORMAL. NELY WINDS OUTSIDE OF THE MTNS WILL BECOME GUSTY WITH MIXING ACROSS THE UPSTATE AND NE GA...AND POSSIBLY PARTS OF NC...BY MID MORNING AS MIXING BEGINS. GUSTS SHUD TAPER OF FOR THE AFTERNOON. WINDS ACROSS THE MTNS WILL BE SLY AND COULD SEE GUSTS FOR THE AFTERNOON. ALTHOUGH SFC WINDS WILL REMAIN NELY OUTSIDE OF THE MTNS TONIGHT WITH HIGH PRESSURE REMAINING IN PLACE...LOW LEVEL FLOW BECOMES SLY AHEAD OF AN APPROACHING SHORT WAVE IN THE SWLY UPPER FLOW AND A DEVELOPING GULF OF MEXICO SFC LOW. GUIDANCE NOW INDICATES LOW LEVEL MOISTURE WILL MOVE INTO THE AREA FROM THE SOUTH AS THE SHORT WAVE APPROACHES THE AREA. LOWS SHUD BE QUITE A BIT WARMER THAN PREVIOUS NITES WITH INCREASING CLOUDS AND MODERATING AIR MASS. LOWS STILL END UP AROUND 5 DEGREES BELOW NORMAL...AND COULD LEAD TO PATCHY FROST ACROSS THE NC MTNS.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... AS OF 240 AM THURSDAY...THE GFS AND ECMWF INDICATE THAT AN AMPLIFIED H5 TROUGH WILL RIPPLE OVER THE DEEP SOUTH ON FRIDAY. BOTH SOLUTIONS SHOW THE TROUGH CLOSING OFF OVER S. GA AND N. FL...WITH THE GFS NORTH OF THE ECMWF. AT THE SFC...LOW PRESSURE WILL LIKELY ORGANIZE ALONG THE GA/FL LINE...WITH NEW ENGLAND CENTERED HIGH PRESSURE RIDGING ACROSS THE WESTERN CAROLINAS. THERE IS STRONG AGREEMENT WITH PLACEMENT OF DEEP MOISTURE AND LIFT ALONG AND EAST OF THE SFC AND MID LEVEL LOW. HOWEVER...MODEL AGREEMENT IS LOW ACROSS THE WESTERN CAROLINAS...WITH THE GFS AND ECMWF TRENDING WETTER ACROSS THE CWA AND NAM REMAINING DRY. BASED ON MODEL TRENDS...I WILL HIGHLIGHT THE MTNS...UPPER SAVANNAH RIVER VALLEY...AND EASTERN PIEDMONT WITH CHC POPS FOR SHRA. IN ADDITION...SKY COVER WILL LIKELY FAVOR MOSTLY CLOUDY CONDITIONS. A BLEND OF PREFERRED MOS GUIDANCE SUPPORTS HIGHS ON FRIDAY IN THE UPPER 50S. FRIDAY NIGHT AND SATURDAY...A BAND OF CLOUD COVER AND DEFORMATION FORCING MAY LINGER ACROSS THE WESTERN CAROLINAS. THIS BAND WILL LIKELY SLOWLY DRIFT EASTWARD THROUGH SATURDAY. THE FORECAST WILL INDICATE MOSTLY CLOUDY CONDITIONS WITH SCHC POPS FRIDAY NIGHT...DECREASING FROM WEST TO EAST DURING THE DAYLIGHT HOURS ON SATURDAY. SATURDAY HIGHS ARE VERY CHALLENGING...WITH THE PRESENCE OF CLOUDS AND SHRA WILL LIKELY IMPACT TEMPS BY 10 TO 15 DEGREES. AT THIS TIME...I WILL FORECAST HIGHS AROUND 5 DEGREES BELOW NORMAL. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 3 AM THURSDAY...SUNDAY AND MONDAY...MEDIUM RANGE MODELS INDICATE THAT THE MID LEVEL CLOSED LOW WILL DRIFT EAST OVER THE WESTERN ATLANTIC AS MID LEVEL RIDGING INCREASES EAST OF THE MISSISSIPPI RIVER VALLEY. THIS PATTERN SHOULD RESULT IN WEAK SFC HIGH PRESSURE AND DRY AIR TO BUILD WEST TO EAST ACROSS THE FORECAST AREA SUNDAY AND MONDAY. HIGH TEMPERATURES WILL LIKELY RANGE WITHIN 2 TO 4 DEGREES OF NORMAL. ON TUESDAY...THE GFS AND ECMWF INDICATE THAT A MID LEVEL SHORT WAVE WILL RIPPLE OVER THE FORECAST AREA DURING THE DAYLIGHT HOURS. AT THE SFC...A WEAK COLD FRONT IS TIMED TO SWEEP ACROSS THE SOUTHERN APPALACHIAN REGION DURING THE AFTERNOON. BOTH SOLUTIONS INDICATES THAT A FIELD OF WEAK CAPE WILL EXIST ALONG AND AHEAD OF THE COLD FRONT. THE APPROACH OF THE MID LEVEL S/W AND COLD FRONT...COMBINED WITH WEAK INSTABILITY SHOULD YIELD AT LEAST SCT SHRA/TSRA. DRY CANADIAN HIGH PRESSURE SHOULD BUILD ACROSS THE REGION ON WEDNESDAY. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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AT KCLT AND ELSEWHERE...CIRRUS HAS OVERSPREAD THE AREA AND WILL CONTINUE THRU THE PERIOD. GUIDANCE NOW IN BETTER AGREEMENT ON LOW VFR CLOUDS MOVING IN FROM THE SOUTH DURING THE EVENING AND BECOMING BKN OVERNIGHT. MVFR CIGS CANNOT BE RULED OUT BEFORE DAYBREAK...BUT BULK OF THE GUIDANCE KEEPS THEM LOW VFR. NELY WIND THIS MORNING BECOMES GUSTY WITH MIXING BY MID-MORNING ACROSS THE UPSTATE...THEN WEAKENS DURING THE AFTERNOON AS IT TURNS ENE. KAVL THE EXCEPTION WHERE LIGHT NLY WIND EARLY THIS MORNING BECOMES SLY BEFORE NOON THEN BECOMES GUSTY FOR AFTERNOON. KAVL WIND RETURNS TO LIGHT NLY DURING THE EVENING. ELSEHWERE...WINDS TURN BACK TO NELY BUT REMAIN ABOVE THE LIGHT CATEGORY. OUTLOOK...CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE SYSTEM DEVELOPS ALONG THE COAST. CONFIDENCE TABLE... 11-17Z 17-23Z 23-05Z 05-11Z KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 97% 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
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR GAZ010-017. FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR GAZ018-026-028- 029. NC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NCZ035>037-048- 051>053-056>059-062>065-068>072-082-501>510. SC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR SCZ003-006>009- 011>014-019. FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR SCZ001-002-004- 005-010. && $$ SYNOPSIS...NED NEAR TERM...RWH SHORT TERM...NED LONG TERM...NED AVIATION...RWH

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