725 FXUS62 KGSP 230731 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 231 AM EST SUN NOV 23 2008 .SYNOPSIS... COOL HIGH PRESSURE OVER THE SOUTHEAST STATES WILL MOVE OFF THE CAROLINA COAST BY EARLY MONDAY. THE NEXT COLD FRONT WILL REACH OUR AREA MONDAY EVENING...FOLLOWED BY NORTHWEST FLOW AND COOLER TEMPERATURES THROUGH THE MIDDLE OF NEXT WEEK. ANOTHER RIDGE OF HIGH PRESSURE WILL BUILD IN FOR THE REMAINDER OF THE WEEK...WHILE ANOTHER FRONT APPROACHES THE AREA NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... STRONG MID-TROPOSPHERIC WARM ADVECTION AHEAD OF A SHORT WAVE OVER NRN TN HAS RESULTED IN MORE CLOUD COVER THAN ORIGINALLY EXPECTED EARLY THIS MORNING. LOCAL 88D/S ARE ALSO SHOWING RETURNS WITH THE CLOUD DECK...MEANING THERE IS QUITE A BIT OF VIRGA UP THERE AS WELL. THE LOWEST 10KFT OF THE ATMOSPHERE IS VERY DRY THIS MORNING...THOUGH THERE IS A CHANCE FOR A LITTLE SLEET OR SNOW AT THE HIGHER ELEVATIONS...AND I/VE ADDED A FEW SLIGHT CHANCE PIXELS FOR THIS TO THE GRIDS AOA 5KFT. STRONG NVA SETS UP AS THE WAVE GOES BY...CLEARING SKIES BY 12 UTC. MAX TEMPS SHOULD GENERALLY BE IN THE LOWER TO MID 50S TODAY OVER THE FOOTHILLS AND PIEDMONT PER LOCAL THICKNESS SCHEMES. THE MOUNTAINS WILL BE A LITTLE COOLER...BUT EVEN THERE WE SHOULD HIT 50 OR SO IN THE LOWER VALLEYS. VERY LATE TONIGHT STRENGTHENING LLVL WARM ADVECTION SHOULD BRING CLOUDS INTO THE SW NC MOUNTAINS. NAM MODEL SOUNDINGS ARE ONLY SATURATED UP TO ABOUT 750 MB BY 12 UTC...AND THE GFS IS A LITTLE DRIER THAN THAT. NEITHER MODEL HAS MUCH SYNOPTIC SCALE ASCENT UNTIL LATER IN THE MORNING...SO I/VE KEPT POPS OUT OF THE FORECAST FOR TONIGHT. I RAISED MIN TEMPS AND DEWPOINTS AS WELL OWING TO THE STRENGTHENING RETURN FLOW. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... AS OF 210 AM SUNDAY...THE NAM AND GFS REMAIN IN VERY GOOD AGREEMENT IN TIMING PRECIP ASSOCIATED WITH FRONTAL BAND INTO THE REGION MONDAY...WITH AT LEAST LIGHT PRECIP EXPECTED TO MAKE ITS WAY INTO THE SOUTHWEST NC MTNS BY NOON. CONSIDERING THE VERY DRY NATURE OF THE PRE-FRONTAL AIRMASS...AND THE EXPECTED COOL START TO MON MORNING...WINTRY PRECIP CANNOT BE RULED OUT AT ONSET. IN FACT...GFS FORECAST SOUNDINGS SUPPORT A BRIEF PERIOD OF FZRA/IP ACROSS THE HIGHER ELEVATIONS EARLY IN THE EVENT. WE WILL CARRY SLIGHT TO LOW CHANCES FOR WINTRY PRECIP MON MORNING...BEFORE WARM ADVECTION ERADICATES THE COLD AIR DURING THE EARLY PART OF THE AFTERNOON. POPS WILL BE INCREASED TO CATEGORICAL (MTNS) TO LIKELY (PIEDMONT) MON AFTERNOON...AS GOOD FORCING/MOISTURE TRANSPORT SHOULD BE MAINTAINED ACROSS THE CWFA. HOWEVER...QPF SHOULD BE RATHER LIGHT...RANGING FROM A HALF INCH OR SO ACROSS THE WESTERN MTNS...TO AROUND A TENTH OF AN INCH ACROSS THE SOUTHEAST ZONES. THE MODELS BEGIN TO DIVERGE MON NIGHT INTO TUE IN THEIR HANDLING OF THE POST-FRONTAL/NORTHWEST FLOW ENVIRONMENT. WHILE THE NAM IS QUITE DRY UPSTREAM OF THE SOUTHERN APPALACHIANS...THE GFS FEATURES AN EXTENDED PERIOD OF VERY MOIST UPSLOPE FLOW. IN FACT...THE GFS SUGGESTS THERE IS THE POTENTIAL FOR A HEAVY NORTHWEST FLOW SNOW EVENT LATE MON NIGHT INTO TUE...AS THE TEMP STRUCTURE...SYNOPTIC PATTERN...AND MOISTURE DEPTH ARE ALL SUPPORTIVE OF SUCH AN EVENT. CONSIDERING MODEL PERFORMANCE THUS FAR IN THE SEASON...WE WILL LEAN HEAVILY TOWARD THE WETTER GFS SOLUTION THROUGH MID-WEEK. THIS WILL RESULT IN A FORECAST OF LIGHT ACCUMULATIONS OF SNOW ACROSS THE FAR WESTERN MTNS FROM LATE MON NIGHT THROUGH EARLY WED. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... AS OF 200 AM SUNDAY...THE MEDIUM RANGE BEGINS 00Z THURS WITH A SFC HIGH BUILDING BACK OVER THE SE CONUS AND SFC FLOW WEAKENING AND TURNING MORE SOUTHERLY. MODEL CONSENSUS REMAINS PRETTY GOOD FOR THE FIRST 36 HRS OR SO OF THE PERIOD...HOWEVER AFTER THAT THE GFS CONTINUES TO BE CONSIDERABLY FASTER THAN THE ECMWF WRT AN UPPER LVL SHORT WAVE AND ITS ASSOCIATED SFC LOW THAT APPROACHES THE CWA. BY 12Z SAT...THE LATEST GFS RUN HAS THIS LOW OVER WEST VIRGINIA WHILE THE ECMWF PLACES IT OVER ARKANSAS. DECIDED TO GO WITH A BLEND OF THE TWO WHICH RESULTED IN A SOLUTION THAT IS CLOSER TO THE 00Z GFS. WITH THAT SAID...I DID NOT NEED TO CHANGE THE SENSIBLE FCST VERY MUCH. I LEFT SLIGHT CHANCE POPS OVER THE ENTIRE CWA FOR SAT AND THE FIRST HALF OF SUN WITH NO QPF INCLUDED YET. THE FIRST PART OF THE FORECAST SHOULD REMAIN DRY W/ THE SFC RIDGE OVER THE AREA. TEMPS REMAIN A BIT TRICKY ON DAYS 6 AND 7 WITH A LOT RIDING ON THE DEVELOPMENT OF THE SFC LOW AND TIMING OF THE FROPA. I KEPT MAX TEMPS IN THE MID 50S FOR THE UPSTATE AND LOW TO MID 40S FOR THE NC MOUNTAINS. MIN TEMPS SHOULD SHOW A STEADY WARMING TREND AND REACH THE UPPER 30S OVER GSP BY EARLY SUN. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... MID LEVEL CLOUD DECK WILL PUSH EAST OF THE REGION BY 12 UTC. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT...THOUGH FAVORING A SOUTHERLY COMPONENT WHEN THE AIR DOES STIR. AFTER SUNRISE WINDS WILL INCREASE OUT OF THE S TO SW AT SPEEDS UNDER 10 KTS. OUTLOOK...A COLD FRONT WILL MOVE THROUGH THE AREA MON WITH CHANCE OF SHOWERS AND CIG/VSBY RESTRICTIONS. EXPECT GUSTY NW WINDS BEHIND THE FRONT MON NIGHT...CONTINUING THROUGH MID WEEK. SCT SNOW SHOWERS AND MVFR CEILINGS PSBL KAVL MON NIGHT THRU TUE NIGHT IN MOIST NW FLOW. && .FIRE WEATHER... DEWPOINTS OVER NE GA WILL BE A LITTLE HIGHER TODAY...BUT SO WILL TEMPERATURES. I/M RIGHT AT 4 HRS OF 25 PERCENT OR LOWER RH/S IN MY NE GA ZONES...SO I/LL KEEP THE RED FLAG WARNING FOR THAT AREA FOR TODAY. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...RED FLAG WARNING FROM 10 AM THIS MORNING TO 7 PM EST THIS EVENING FOR GAZ010-017-018-026-028-029. NC...NONE. SC...NONE. && $$ SYNOPSIS...DEO NEAR TERM...MCAVOY SHORT TERM...JDL LONG TERM...JPT AVIATION...MCAVOY FIRE WEATHER...MCAVOY