Area Forecast Discussion


675 
FXUS62 KGSP 161434
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1034 AM EDT WED OCT 16 2013
.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN OVER THE AREA TODAY AS A COLD FRONT 
APPROACHES FROM THE WEST. THE FRONT WILL SLOWLY CROSS THE AREA 
TONIGHT AND THURSDAY. HIGH PRESSURE WILL RETURN LATE IN THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM...LOW CLOUDS DID ROTATE WEST INTO THE I-77 CORRIDOR 
BUT ARE NOW SCATTERING OUT. HOWEVER...CLOUDS ARE MOVING IN FROM THE 
WEST AHEAD OF THE NEXT COLD FRONT. THEREFORE...HAVE STARTED WITH 
CURRENT CONDITIONS AND BLENDED INTO THE GOING AFTERNOON FCST. TEMPS 
WILL LIKELY BE SLIGHTLY COOLER THAN PREV FCST GIVEN THE MORNING 
CLOUDS AND EXPECTED AFTERNOON CLOUDS. OTHERWISE...GOING FCST LOOKS 
ON TRACK WITH SHRA SLOWLY MOVING INTO THE MTNS LATE THIS AFTERNOON 
INTO EARLY EVENING. HAVE MADE SOME COSMETIC CHANGES TO LATER PERIODS 
FOR INTERNAL CONSISTENCY PROBLEMS.
AS OF 455 AM EDT WEDNESDAY...IT/S REALLY FOGGED UP IN THE UPPER AND 
CENTRAL FRENCH BROAD VALLEY THIS MORNING. THE REASON FOR THE FOG IS 
A LACK OF MID AND HIGH LEVEL CLOUD COVER AS THEY HAVE STRUGGLED 
MAKING IT OVER THE SHORT WAVE RIDGE THIS MORNING. I/VE CUT BACK SKY 
COVER OVER MANY ZONES FOR THE NEXT FEW HOURS TO ACCOUNT FOR THIS. I 
WOULD STILL EXPECT AN INCREASE IN CLOUD COVER AFTER SUNRISE ACROSS 
THE REGION BUT ESPECIALLY OVER THE FOOTHILLS AND MOUNTAINS. 
AS OF 210 AM EDT WEDNESDAY...LOW CLOUDS WILL PERSIST ALONG AND EAST 
OF I-77 THROUGH SUNRISE...WITH MID AND HIGH LEVEL CLOUDS AFFECTING 
THE REST OF THE REGION. THERE WILL ALSO BE PATCHES OF STRATUS AND 
FOG OVER THE NC MTNS...THOUGH IT SHOULDN/T BE WIDESPREAD ON ACCOUNT 
OF DISRUPTION OF RADIATIONAL COOLING BY THE HIGHER CLOUD DECK. EVEN 
SOME OF THE PIEDMONT AND FOOTHILL LAKES AND RIVERS WILL SEE PATCHY 
FOG AND STRATUS EARLY ON.
THE GFS LIMPS SOME LIGHT PCPN INTO THE SOUTHWEST MOUNTAINS BY 00 UTC 
TONIGHT WHILE THE NAM IS DRY THROUGH THIS TIME. I TRIMMED POPS BACK 
A LITTLE AS IT APPEARS THAT THE OVERALL TREND FOR A SLOWER EASTWARD 
PROGRESSION OF THE PCPN. EVEN WITH THE HIGH CLOUD COVER...WE SHOULD 
SEE TEMPERATURES A FEW DEGREES ABOVE NORMAL FOR TODAY.
PCPN CHANCES SHOULD REMAIN LOW UNTIL LATE WED NIGHT AS MOST OF THE 
PCPN NOW LOOKS TO ACCOMPANY A WEAK FRONTAL WAVE THAT QUICKLY MOVES 
ACROSS THE SOUTHERN APPALACHIANS DURING THE DAY ON THURSDAY. POPS 
WERE RAISED INTO THE LIKELY CATEGORY LATE TONIGHT AS THE GFS 
CONTINUES TO BRING PCPN ACROSS MUCH OF THE CENTRAL AND SRN MTNS 
TOWARD MORNING. THE STRONGEST LLVL WARM ADVECTION IS FOUND ON THE 
NAM...THOUGH IT RESIDES MAINLY OVER WRN TN. THEREFORE I DON/T 
FORCING FOR MORE THAN A TENTH TO A QUARTER INCH OF RAINFALL OVER THE 
MTN ZONES BY 12 UTC THU.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AT 230 AM EDT WEDNESDAY...A BROAD UPPER TROUGH WILL AMPLIFY OVER THE 
CONTINENTAL USA ON THURSDAY AND FRIDAY. A WELL DEFINED SHORTWAVE WIL 
CROSS THE GREAT LAKES AND OH VALLEY ON THURSDAY...BRUSHING THE 
SOUTHERN APPALACHIANS. ON FRIDAY AN EVEN STRONGER SHORTWAVE DIVES 
INTO THE TROUGH AXIS OVER THE PLAINS...WHILE BOTH THE NAM AND GFS 
SHOW A MINOR IMPULSE EMANATING FROM THE CENTRAL GULF COAST.
A COLD FRONT WILL CROSS OUR AREA FROM THE NW ON THURSDAY... 
ACCOMPANIED BY WIDESPREAD PRECIPITATION. MODEL TIME HEIGHTS SHOW 
DEEP MOISTURE AND ARE FINALLY SHOWING SOME UPWARD MOTION...BUT LOW 
LEVEL WINDS ARE PARALLEL TO THE BLUE RIDGE...LIMITING UPSLOPE FLOW. 
INSTABILITY WILL BE RATHER LIMITED THURSDAY...HOWEVER SHEAR WILL BE 
PRESENT. AT THIS TIME CONFIDENCE IS TO LOW TO MENTION A THREAT OF 
SEVERE WEATHER IN THE HAZARDOUS WEATHER OUTLOOK.
DRIER AIR WILL MOVE IN BEHIND THE FRONT ON THURSDAY NIGHT AND 
FRIDAY....WHILE THE FRONT STALLS NEAR THE COAST. A SURFACE WAVE 
MOVES UP THE FRONT FRIDAY NIGHT...SPREADING MOISTURE BACK 
INLAND....WHILE ANOTHER COLD FRONT APPROACHES THE MOUNTAINS FROM 
THE NW. THE RESULT OF THESE TWO SYSTEMS WILL BE INCREASING CLOUDS 
COVER FRIDAY NIGHT. TEMPERATURES WILL RUN NEAR NORMAL.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AT 230 AM EDT WEDNESDAY...ON SATURDAY MORNING A BROAD AND POSITIVELY 
TILTED UPPER TROUGH WILL EXTEND FROM ONTARIO TO BAJA CALIFORNIA. 
THIS AXIS PROGRESSES VERY SLOWLY...EXTENDING FROM ROUGHLY QUEBEC TO 
TX BY TUESDAY.
A SLOW MOVING COLD FRONT WILL EXTEND FROM THE SC COAST TO THE GULF 
COAST ON SATURDAY MORNING...WHILE ANOTHER COLD FRONT WILL BE OVER 
THE OH AND MID MS RIVER VALLEYS. BY SUNDAY THE FIRST FRONT WILL BE 
OVER THE GULF STREAM AND CENTRAL GULF OF MEXICO...WHILE THE SECOND 
FRONT MOVES OFF THE VA COAST...AND HIGH PRESSURE BUILD OVER THE 
SOUTHERN APPALACHIANS FROM THE W. THE SURFACE HIGH REACHES THE 
CENTRAL APPALACHIANS ON MONDAY...WHILE THE GULF OF MEXICO FRONT 
STALLS. ON TUESDAY THE HIGH CENTER SETTLES OVER THE SOUTHERN 
APPALACHIANS...WHILE THE GULF FRONT MOVES NORTH TO THE GULF COAST.
CLOUDS AND PRECIPITATION MAY LINGER BEHIND THE FIRST FRONT ON 
SATURDAY AS A SURFACE WAVE MOVES UP THE BOUNDARY...WITH THE PIEDMONT 
SEEING THE GREATEST EFFECT. DRYING WILL OCCUR ON SUNDAY AND MONDAY 
AS HIGH PRESSURE MOVES IN BEHIND THE DEPARTING FRONT. BY 
TUESDAY...ISENTROPIC UPGLIDE OVER THE GULF COAST FRONT MAY RESULT 
IN INCREASING CLOUD COVER...BUT PRECIPITATION CHANCES APPEAR LIMITED 
THIS FAR NORTH OF THE BOUNDARY. TEMPERATURES WILL RUN SEVERAL 
DEGREES BELOW NORMAL.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...LOW CLOUDS THAT SPREAD IN NEAR DAYBREAK SHUD REMAIN SCT... 
BUT CANNOT RULE OUT A BRIEF LOW VFR CIG THIS AFTERNOON. LIGHT AND 
VARIABLE WINDS WILL GRADUALLY TURN OUT OF THE SOUTH TO SOUTHWEST AT 
6 KTS OR LESS THIS AFTN. AND LOW CIGS OR PCPN SHOULD STAY WELL WEST 
OF THE AIRFIELD THROUGH 12 UTC THU. 
AT KAVL...FOG SLOWLY LIFTING BUT SHUD BE GONE BEFORE NOON. OTHERWISE 
LOW VFR CLOUDS WILL GRADUALLY THICKEN AS THEY MOVE IN FROM THE WEST 
THROUGH THE DAY. BY LATER TONIGHT SHOWERY PCPN SHOULD SPREAD ACROSS 
THE MOUNTAINS. PREVAILING SHOWERS AND LOWER CIGS WERE CARRIED 
STARTING AT 11 UTC.  
ELSEWHERE...ANY FOG HAS DISSIPATED...BUT MVFR CIGS SLOWER TO LIFT 
ACROSS THE FOOTHILLS. EXPECT VFR BY AFTERNOON...BUT LOW VFR CIGS ARE 
POSSIBLE FROM TIME TO TIME. LIGHT WINDS WILL TURN OUT OF THE SOUTH 
THIS AFTN AS MID AND HIGH LEVEL CLOUDS GRADUALLY THICKEN AND 
LOWER.      
OUTLOOK...LOW PRESSURE WILL MOVE QUICKLY NORTHEASTWARD...ACROSS THE 
SOUTHERN APPALACHIANS ON THURSDAY. THIS WILL SPREAD SHOWERS ACROSS 
THE MOUNTAINS WEDNESDAY NIGHT AND OVER THE REST OF THE REGION ON 
THURSDAY. IF THE PCPN IS HEAVY ENOUGH...THEN SOME RESTRICTIONS ARE 
LIKELY DURING THIS TIME. IMPROVING CONDITIONS ARE EXPECTED THURSDAY 
NIGHT AND FRIDAY. LOWER CIGS ARE POSSIBLE AGAIN FRIDAY NIGHT AND 
SATURDAY AS ANOTHER WAVE OF LOW PRESSURE DEVELOPS ALONG THE COAST.
CONFIDENCE TABLE...
            14-20Z        20-02Z        02-08Z        08-14Z 
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%     
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%     
KAVL       HIGH  93%     HIGH 100%     HIGH  88%     MED   74%     
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%     
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%     
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%     
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...JAT
NEAR TERM...MCAVOY/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...MCAVOY/RWH