Area Forecast Discussion
Issued by NWS Greer, SC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KGSP 210254 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 954 PM EST THU NOV 20 2014 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION TONIGHT WITH HIGH PRESSURE BUILDING IN ON FRIDAY AND LINGERING INTO SATURDAY. ABUNDANT MOISTURE WILL RETURN ON SUNDAY AHEAD OF A LOW PRESSURE SYSTEM LIFTING FROM TEXAS TO THE GREAT LAKES. THE WEATHER MAY REMAIN UNSETTLED EARLY NEXT WEEK AS ANOTHER COLD FRONT APPROACHES FROM THE WEST. && .NEAR TERM /THROUGH FRIDAY/... AS OF 945 PM...FOR THE 0230 UTC UPDATE...ADJUSTED THE HOURLY TEMP AND DEWPT TRENDS HEADING INTO THE OVERNIGHT HOURS TO MATCH UP WITH THE METARS. OTHERWISE...NO CHANGES NEEDED. AS OF 630 PM...NO SIGNIFICANT CHANGES FOR THE 2330 UTC UPDATE. I UPDATED THE SKY AND WINDS WITH THE LATEST GUIDANCE FOR THE 00Z TAFS. OTHERWISE...NO CHANGES NEEDED. AS OF 200 PM EST THURSDAY...AN UPPER TROUGH AXIS IS FORECAST TO SWING ACROSS THE SOUTHEAST THIS EVENING THROUGH TONIGHT AND OFF THE ATLANTIC COAST BY FRI MORNING. THIS WILL PUSH A TRAILING DRY COLD FRONT THROUGH THE FORECAST AREA THIS EVENING INTO TONIGHT WITH SW/WSW WINDS VEERING TO THE NW IN ITS WAKE. CONDITIONS SHOULD REMAIN DRY WITH CONSIDERABLE LLVL CLOUDINESS CAN BE SEEN ALONG THE TN BORDER. WITH GOOD NW DOWNSLOPING EFFECT...MORNING LOWS ON FRIDAY WILL BE A FEW DEGREES WARMER THAN THIS MORNING/S LOW MAINLY EAST OF THE MTNS. DURING THE DAY ON FRIDAY...H5 HEIGHTS WILL GRADUALLY RISE OVER THE REGION AS A WEAK UPPER RIDGE BUILDS IN FROM THE WEST. THIS WILL ALLOW SURFACE HIGH CENTERED OVER THE OHIO VALLEY TO MIGRATE INTO THE MID ATLANTIC STATES BY FRI AFTERNOON...SETTING UP A COLD AIR WEDGE OVER OUR CWA. THEREFORE...WEE WILL SEE CONTINUED DRY CONDITIONS WITH AFTERNOON TEMPS RUNNING AROUND 7-10 DEGREES BELOW NORMAL. && .SHORT TERM /FRIDAY NIGHT THROUGH MONDAY NIGHT/... AS OF 145 PM EST THURSDAY...OUR MAIN FOCUS FOR THE SHORT RANGE PERIOD IS THE SYSTEM EXPECTED TO MOVE THROUGH ON SUNDAY. PRIOR TO THAT...THE WEATHER SHOULD BE FAIRLY QUIET FOR THE FIRST HALF OF THE WEEKEND. HEIGHTS WILL BUILD AS AN UPPER RIDGE AXIS CROSSES LATE SATURDAY. THAT WILL SUPPORT SURFACE HIGH PRESSURE OVER THE MID ATLANTIC AND CAROLINAS FRIDAY NIGHT THAT SLOWLY DRIFTS OFFSHORE ON SATURDAY. THEN...THINGS GO QUICKLY DOWNHILL SATURDAY NIGHT. A STRONG SHORT WAVE IS FCST TO COME OUT ACROSS TX SATURDAY NIGHT TO AR/MS DELTA REGION BY 12Z SUNDAY. THE PATTERN AMPLIFIES IN RESPONSE WITH THE FLOW VEERING SW ACROSS THE SOUTHEASTERN UNITED STATES BY SUNRISE ON SUNDAY. THIS SHOULD OPEN UP THE EASTERN GULF AND ATLANTIC AND LET MOISTURE RETURN BEGINNING LATE SATURDAY EVENING. A MOISTENING LOW LEVEL SE FLOW WILL INCREASE SATURDAY EVENING WHICH SHOULD BEGIN TO FORCE THE DEVELOPMENT OF LIGHT PRECIP NEAR THE SC/NE GEORGIA BLUE RIDGE BY 06Z. PRECIP CHANCES BEGIN THERE AND GRADUALLY EXPAND UP THE BLUE RIDGE OVERNIGHT AND OUT OVER THE PIEDMONT AND FOOTHILLS SUNDAY MORNING...FIRST IN RESPONSE TO THE MECHANICAL LIFT WITH THE STRENGTHENING SE FLOW...THEN IN RESPONSE TO THE DEVELOPMENT OF ISENTROPIC LIFT FROM THE S AND UPPER DIVERGENCE FROM THE SW IN THE 06Z TO 12Z SUNDAY TIME RANGE...AND THE APPROACH OF A VORT MAX AFTER 12Z. FORTUNATELY...WARM ADVECTION SHOULD KEEP TEMPS ABOVE FREEZING...SO PRECIP TYPE SHOULD NOT BE AN ISSUE. PRECIP CHANCES OVERALL LOOK VERY GOOD...SO THE POP WAS ALLOWED TO RAMP UP TO CATEGORICAL EVERYWHERE BY SUNDAY AFTERNOON. THERE ARE A FEW ISSUES WITH THIS FCST...CHIEFLY THE SEVERE WEATHER POTENTIAL. AS THE PRECIP DEVELOPS...THE RETREATING SFC HIGH SHOULD BE IN POSITION TO ALLOW FOR AN IN SITU COLD AIR DAMMING WEDGE TO DEVELOP IN THE USUAL LOCATION ON SUNDAY MORNING. ONCE ESTABLISHED... THE WEDGE WILL BE DIFFICULT TO DISLODGE AND SHOULD PREVENT DESTABILIZATION ACROSS ALL BUT PERHAPS THE LAKELANDS. THE SHEAR AND HELICITY SHOULD BE VERY STRONG. THE MAIN SHORT WAVE ACQUIRES A SHARP NEGATIVE TILT AS IT LIFTS OUT TO OUR WEST ON SUNDAY...WHICH BACKS THE LOW LEVEL FLOW IN THE AFTERNOON AS THE LOW LEVEL JET TRANSLATES OVERHEAD ATOP THE WEDGE. AT THIS POINT...THE SITUATION DOES NOT APPEAR FAVORABLE FOR SEVERE STORMS ACROSS MOST OF THE AREA AS WE WILL HAVE THE HIGH SHEAR BUT NOT THE LOW CAPE. EVEN THE USUALLY MORE UNSTABLE NAM KEEPS THE LOW CAPE S OF I-20 THRU 00Z MONDAY. WHATS MORE...WE ALSO LACK THE STRONG SRN STREAM ADVECTIVE SHORT WAVE THAT WE OFTEN SEE IN EVENTS THAT RESULT IN SEVERE STORMS DURING HIGH SHEAR LOW CAPE SITUATIONS. THAT WAVE STAYS WELL TO OUR W AND NW. HEAVY RAIN MIGHT BE THE GREATER CONCERN...BUT EVEN THAT LOOKS SUSPECT AS THE STRONGER STORMS MAY LIFT ACROSS THE COASTAL PLAIN... IN THE WARMER AIR AND NEAR THE WEDGE BOUNDARY...WHICH WILL LIMIT THE MOISTURE TRANSPORT AND PRECIP RATES ACROSS OUR REGION. FOR NOW...WILL NOT MENTION ANY SEVERE WEATHER POSSIBILITIES IN THE HWO. THE MAIN PRECIP SHOULD LIFT OFF TO THE NE SUNDAY EVENING HAVE KEPT SOME LINGERING PRECIP CHANCE PER THE MODEL GUIDANCE AND NEIGHBORING FCST OFFICES. && .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 250 PM THURSDAY...ON MONDAY...THE SFC COLD FRONT IS EXPECTED TO RUN NORTH TO SOUTH ACROSS MIDDLE KENTUCKY AND TENNESSEE BY 12Z MONDAY. AT H5...THE LONGWAVE TROUGH AXIS WILL AMPLIFY ACROSS THE CENTRAL CONUS INTO THE SOUTHERN PLAINS. THE PATTERN SHOULD PROVIDE WARM LLVL TEMPS AND THICKNESSES ACROSS THE FORECAST AREA ON MONDAY. USING A BLEND OF GUIDANCE...I WILL FORECAST HIGH TEMPERATURES TO RANGE FROM THE MID 60S WITHIN THE MTN VALLEYS TO THE LOW 70S EAST. I WILL KEEP A MENTION OF CHC POPS ACROSS THE CWA WITH THE PASSAGE OF THE COLD FRONT. TUESDAY...THE LONGWAVE TROUGH WILL APPROACH THE SOUTHEAST THROUGH THE DAY...RESULTING THE PASSAGE A FEW WEAK VORTS. I WILL KEEP SCHC TO CHC POPS ACROSS THE REGION. MIN TEMPERATURES SHOULD REMAIN AROUND 5 DEGREES ABOVE NORMAL. HIGH TEMPERATURES ARE FORECAST TO RANGE FROM THE MID 50S WITHIN THE MTNS VALLEYS TO AROUND 60 EAST. WEAK CAA WILL DEVELOP ACROSS THE REGION TUESDAY EVENING AND NIGHT. H85 FLOW IS FORECAST TO REMAIN FROM THE WNW AROUND 20 KTS...SUPPORTING WEAK NORTHWEST FLOW SHOWERS ALONG THE TN BORDER AND RIDGES. PRECIP IS EXPECTED TO MIX OVER FROM RAIN TO SNOW DURING THE EVENING...WITH SNOW REMAIN DURING THE NIGHT. ACCUMS APPEARS TO REMAIN MININMAL DURING THE PERIOD OF NWFS. WED THROUGH THURS...THE ECMWF INDICATES THAT DRY ZONAL FLOW WILL DEVELOP ACROSS THE REGION. THE GFS INDICATES THAT A VERY STRONG MID LEVEL SHORT WAVE WILL RIPPLE ACROSS THE REGION THANKSGIVING AFTERNOON...WHICH COULD RESULT IN SIGNIFICANT WEATHER. HOWEVER...NATIONAL PREFERRED GUIDANCE IS CLOSE TO THE ECMWF...SO IT WILL BE THE MODEL OF CHOICE. TEMPERATURES WILL REMAIN SLIGHTLY BELOW NORMAL BOTH DAYS. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... AT KCLT AND ELSEWHERE...LITTLE CHANGE NEEDED FOR THE 00Z TAFS. EXPECT VFR CONDITIONS TO PERSIST THROUGH 00Z SATURDAY. SW TO WSW WINDS WILL VEER TO THE NW BY AROUND 6Z AS A DRY COLD FRONT PUSHES THROUGH THE AREA. THE EXCEPTIONS ARE KAVL AND KHKY...WHERE WINDS START OUT NW OR N...AND WILL SHOULD PREVAIL THROUGHOUT THE PERIOD. AS SURFACE HIGH PRESSURE BECOMES CENTERED TO OUR NORTHEAST...N/NW WINDS OVERNIGHT WILL VEER TO THE NE BY FRIDAY MORNING. SKIES SHOULD REMAIN MOSTLY CLEAR UNDER THE RIDGE FOR MOST LOCATIONS. OUTLOOK...DRY HIGH PRESSURE LINGERS FRIDAY NIGHT AND SATURDAY. CLOUDS AND PRECIPITATION RETURN TO THE AREA ON SUNDAY WITH ANOTHER FRONT...AND ASSOCIATED RESTRICTIONS ARE POSSIBLE. BRIEF DRYING FOLLOWS THE FRONT ON MONDAY. CONFIDENCE TABLE... 03-09Z 09-15Z 15-21Z 21-00Z 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...CSH NEAR TERM...ARK/JOH SHORT TERM...PM LONG TERM...NED AVIATION...ARK/JOH

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.