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