Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 201755 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1055 AM EDT MON OCT 20 2014 .SYNOPSIS... DRY CANADIAN HIGH PRESSURE WILL PERSIST ACROSS THE REGION TODAY...WITH A WEAK FRONTAL SYSTEM MOVING INTO THE NORTH CAROLINA MOUNTAINS EARLY TUESDAY. DRY AND SEASONAL HIGH PRESSURE WILL BUILD BACK IN BEHIND AN UPPER LEVEL TROF WEDNESDAY AND REMAIN ACROSS THE AREA THROUGH THE WORK WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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CU FIELD DEVELOPING FROM PARTS OF THE SOUTHERN UPSTATE INTO THE WESTERN PIEDMONT OF NC. OTHERWISE SOME PATCHY CI HERE AND THERE. WE DO NOT SEE MUCH NEED FOR ANY SIGNIFICANT ADJUSTEMENTS IN THE FORECAST OTHER TO MENTION HAVE A BIT MORE CLOUDS WHERE THE CU IS BECOMING MORE OPAQUE. OTHERWISE TEMPERARATURES STILL ON TARGET. MID MORNING DISUSSION... OUR MID MORNING UPDATE WAS TO ADD FOG FOR A FEW HOURS IN THE REST OF THE WESTERN NC RIVER VALLEYS WHERE CIRRUS CLOUDS EXITING AND FOG WAS ABLE TO DEVELOP. MOST OF THAT FOG IS BURNING OFF...WITH THE LAST IN THE LITTLE TENNESSEE RIVER VALLEY...AND THAT SHOULD BE GONE SOON. OTHERWISE THE REMAINDER OF THE FORECAST IS IN GOOD SHAPE...WITH OUR DIURNAL TEMPERATURES AND DEWPOINTS FOLLOWING A DECENT TREND. REMAINDER OF PREVIOUS DISCUSSION... MORNING UPDATE...WITH THICKER CI CROSSING OVERHEAD...TEMPS AND TD/S ARE REMAINING ABOVE FR LEVELS ACROSS THE NC MTNS...BUT ISOL AREAS COULD SEE LIGHT FR THROUGH DAYBREAK. NO SIGFNT CHANGES WERE NEEDED TO THE GRIDS. 430 AM EDT UPDATE...PASSING BKN/OVC CI FIELD CONTINUES ACROSS MAINLY THE NRN ZONES THIS MORNING. EVEN WITH CALM CONDS...TEMPS HAVE REMAINED A COUPLE DEGREES F ABOVE THE FCST CURVE ACROSS THE FB VALLEY AND OVER THE NC PIEDMONT AND UPSTATE. THUS...THE HR/LY TEMP GRIDS WERE ADJ UPWARD A BIT OVER THE NEXT FEW HRS. THE THREAT OF WIDESPREAD FR FORMATION ACROSS THE NRN MTNS LOOKS MINIMAL PER THE LATEST MESONET T/TD DATA...HOWEVER PATCHY DEVELOPMENT IS STILL POSSIBLE BEFORE AND THRU SUNRISE. AS OF 245 AM EDT...SURFACE HIGH PRESSURE WILL CONTINUE TO DOMINATE THE WX PATTERN THIS MORNING AND THROUGH MUCH OF THE NEAR TERM. THIS WILL MAINTAIN FAIRLY WEAK WINDS WITH NOMINAL MIXING IN WEAK LLVL FLOW. UPPER LEVEL CLOUDS ASSOCIATED WITH A PASSING TROF AXIS WILL DIMINISH THROUGHOUT THE DAY...YET FEW/SCT CI WILL LINGER WITH FEW/SCT FAIR WX CU PROBABLE AS WELL. MAX TEMPS WILL BE CLOSE TO NORMAL AND RIGHT IN LINE WITH EXPECTED LLVL THICKNESS VALUES. WITH THE SFC HIGH SHIFTING OFFSHORE...THE INCREASE IN SW/LY TEMP/MOIST FLUX MON WILL MAINTAIN HIGHER MINS OVERNIGHT AS WELL. THIS WILL OFFSET MOST FG AND FR THREATS...HOWEVER SOUNDINGS AND MOS GUIDANCE STILL INDICATE A GOOD PROB FOR LOW VSBY ACROSS THE FRENCH BROAD AND LITTLE TN VALLEYS BEFORE DAYBREAK. AN INCREASE IN STCU WILL OCCUR ACROSS THE NC MTN SPINE AND NRN MTNS OVERNIGHT AS A CLIPPER SYSTEM DIVES OUT OF THE GLAKE REGION AND THIS SHOULD BE ENUF TO DIFFUSE VSBY CONCERNS OVER THESE AREAS. THERE WILL BE ENOUGH MECH LIFT AND SOME ULVL DYNAMICAL AIDE TO ALLOW FOR -SHRA AND SPRINKLES WHICH IS COVERED WITH ISOL POPS MAINLY ACROSS THE NRN FOUR NC MTN COUNTIES. MINS MON NIGHT WILL BE WARMER THAN THIS MORNINGS LOWS BY A COUPLE CATS OR RIGHT AROUND NORMAL.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 305 AM EDT MONDAY...ANOTHER IN A SERIES OF POTENT SHORT WAVE TROUGHS WILL DIG STRONGLY OUT OF THE GREAT LAKES REGION...TOWARD THE SOUTHERN APPALACHIANS AND MID-ATLANTIC EARLY IN THE SHORT TERM PERIOD. THIS WILL INTRODUCE ANOTHER SURGE OF COOL AIR INTO OUR AREA LATE TUE INTO TUE NIGHT. THE SERIES OF WAVES WILL CARVE OUT AN UPPER LOW OVER THE MID-ATLANTIC/NORTHEAST THAT WILL RESULT IN A SOMEWHAT PROTRACTED PERIOD OF NW FLOW ACROSS THE CAROLINAS/NORTH GEORGIA INTO LATE WEEK. A PERIOD OF NW FLOW RAIN SHOWERS WILL BE POSSIBLE... MAINLY TUE NIGHT AS UPSLOPE MOISTURE DEEPENS BRIEFLY WITH THE PASSAGE OF THE UPPER WAVE. HOWEVER...EVEN THEN TENN BORDER POPS SHOULD NOT EXCEED 30 PERCENT OR SO. MOISTURE WILL BECOME MORE SHALLOW BY EARLY WED...BUT STILL EXPECT PLENTY OF LINGERING CLOUD COVER TO PERSIST NEAR THE TENN BORDER THROUGH THE END OF THE PERIOD. MEANWHILE...CLASSIC COOL/MOSTLY CLEAR AUTUMN WEATHER WILL PERSIST SOUTHEAST OF THE BLUE RIDGE... WITH NEAR NORMAL TEMPS ON TUESDAY GIVING WAY TO WEATHER THAT WILL BE 5-10 DEGREES BELOW CLIMO BY WEDNESDAY. DESPITE THIS...CURRENT INDICATIONS ARE THAT CLOUDS AND/OR WIND WILL PRECLUDE MUCH OF A FROST FREEZE CONCERN IN THE MTNS... EXCEPT PERHAPS IN THE SHELTERED VALLEYS OF THE SOUTHWEST MTNS (WHERE THE FROST/FREEZE PROGRAM HAS ALREADY ENDED FOR THE SEASON). && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 315 AM MONDAY...THE PATTERN WILL REMAIN TYPICALLY INACTIVE THROUGH THE MEDIUM RANGE...AS A MEAN LONG WAVE TROUGH WILL GENERALLY BE MAINTAINED NEAR THE EAST COAST THROUGH THE PERIOD. TEMPS WILL MODIFY CLOSER TO CLIMO BY THE WEEKEND...AS HEIGHTS RISE DOWNSTREAM OF DAMPENING SHORT WAVE RIDGE. A CONSENSUS OF THE LATEST GLOBAL MODEL GUIDANCE WOULD SUGGEST PASSAGE OF ANOTHER STRONG SHORT WAVE TROUGH OVER THE WEEKEND...WHICH COULD BRING SMALL CHANCES FOR MOUNTAIN SHOWERS AND COOL US DOWN AGAIN BY THE END OF THE PERIOD. && .AVIATION /18Z MONDAY THROUGH FRIDAY/...
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AT KCLT AND ELSEWHERE...VFR FLIGHT CONDITIONS THROUGHOUT THE TAF PERIOD. HIGH PRESSUE CONTINUES TO MOVE EAST AND RETURN FLOW WAS HELPING SOME SCT CU TO DEVELOP THIS AFTERNOON. THIS MAY MAKE A RUN AT THE CLT AIRFIELD...BUT ABOVE MVFR CONDITIONS. AHEAD OF THE NEXT APPROACHING FRONT...THE MODELS WERE ADVERTISING A BAND OF AC/CI ZIPPING ACROSS THE REGION TONIGHT. WE HAVE FOLLOWED THIS TREND AND INSERTED INTO SAID FORECAST. WINDS SHOULD BE SOUTHERLY...AND WE BUMPED THEM UP A NOTCH...BASED ON SOUNDING DATA. THOSE SHOULD RELAX AT SUNDOWN. FOLLOWING THE AC/CI MOVING THROUGH TONIGHT...AND BEFORE THE LOW CLOUDS CAN START IN THE CAA PATTERN WITH THE NEXT FRONT...THERE MAY BE A WINDOW OF OPPORTUNITY FOR FOG IN THE NC MOUNTAIN VALLEYS/THE NW UPSTATE OF SC/AND NORTHEAST GEORGIA. OUTLOOK...A ROUND OF GUSTY NW WINDS AND MOUNTAIN STRATOCU WILL BE POSSIBLE BEHIND A MOSTLY DRY COLD FRONT LATE TUE INTO EARLY WED. OTHERWISE...VFR CONDITIONS SHOULD PREDOMINATE INTO LATE WEEK. CONFIDENCE TABLE... 10-16Z 16-22Z 22-04Z 04-10Z KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL HIGH 94% 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 89% HIGH 99% 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...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...SBK NEAR TERM...SBK/TS SHORT TERM...JDL LONG TERM...JDL AVIATION...SBK

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