Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 160559
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
159 AM EDT TUE SEP 16 2014

.SYNOPSIS...
A NEARLY STATIONARY FRONT WILL INTERACT WITH AN UPPER DISTURBANCE
WHICH WILL CROSS OUR AREA TONIGHT. A COLD FRONT WILL THEN CROSS THE
AREA IN ITS WAKE ON TUESDAY...USHERING IN SEASONABLY COOL AIR AND
MOSTLY DRY WEATHER LASTING INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 155 AM...ADDITIONAL SHOWER AND EVEN ISLD THUNDERSTORM
DEVELOPMENT HAS OCCURRED THIS MORNING ACROSS THE GA MOUNTAINS AND
SAVANNAH RIVER VALLEY. POPS HAVE BEEN INCREASED TO THE CHANCE RANGE
IN THESE AREAS FOR THE NEXT COUPLE OF HOURS. OTHERWISE...WIDESPREAD
CLOUD COVER AND AREAS OF FOG WILL PERSIST IN MOST AREAS UNTIL AFTER
SUNRISE.

AS OF 1015 PM...A FAIR AMOUNT OF THE LIGHT SHWRS HAVE SURVIVED TO
THE NC PIEDMONT AND EASTERN UPSTATE. SO POPS WERE TWEAKED UP IN
THOSE AREAS TO MID CHC. TO THE WEST...AS THE MID LVL SHORTWAVE
BEGINS TO CROSS THE MTNS...THE BACK EDGE OF THE BETTER FORCING SHUD
PUSH THRU...ALLOWING POPS TO TAPER OFF. THE COMBINATION OF SPOTTY
RAINFALL AND SOME CLEARING OF THE LOWER CLOUDS MAY RESULT IN PATCHY
FOG DEVELOPMENT. HOWEVER...NOT EXPECTING ANY SIGNIFICANT DENSE FOG.
TEMPS LOOK ON TRACK.

AS OF 800 PM...AS MID LVL SHORTWAVE ENTERS THE SRN
APPALACHIANS...SHWRS AND A COUPLE OF TSTMS HAVE DEVELOPED ACRS THE
MTNS AND HEADING EAST. THERE IS STILL NOT MUCH INSTBY TO WORK WITH
EAST OF THE MTNS...SO I EXPECT COVERAGE TO REMAIN SCATTERED...AND
PROBABLY GRADUALLY DISSIPATE THIS EVENING. NO MAJOR CHANGES WERE
MADE TO THE FCST WITH THIS UPDATE.

AS OF 530 PM...A FEW SHOWERS HAVE BEGUN TO DEVELOP ACROSS THE SW AND
CENTRAL NC MTNS...AS A MID LVL SHORTWAVE APPROACHES FROM THE WEST.
THIS AREA IS ALSO THE ONLY AREA THAT HAS ANY SBCAPE PER THE SPC
MESOANALYSIS PAGE...WITH VALUES OF 500-1000 J/KG. THE REST OF THE
AREA IS STILL STABLE...AS STRATUS IS STUBBORN TO SCATTER
OUT...DESPITE INCREASING WESTERLY LLVL FLOW. I UPDATED POPS AND
TEMPS TO MATCH UP WITH THE TRENDS. CANNOT RULE OUT A FEW RUMBLES OF
THUNDER IN THE NC MTNS. OTHERWISE...GENERALLY CLOUDY WITH TEMPS IN
THE LWR-MID 70S HEADING INTO THE EVENING. NO CHANGES WERE MADE FOR
THE OVERNIGHT.

AS OF 220 PM EDT...RADARS REMAIN FAIRLY QUIET ACROSS THE FORECAST
AREA THIS AFTN AS A STABLE SHALLOW COOL SFC LAYER REMAINS IN PLACE
ACROSS THE REGION. ALOFT...WATER VAPOR IMAGERY SHOWS A SRN STREAM
SHORTWAVE MOVING INTO THE MID SOUTH THIS AFTN. IR IMAGERY SHOWS MID
AND HIGH CLOUDS AHEAD OF THIS FEATURE ATOP THE LOWER CLOUDS STILL IN
PLACE ACROSS THE FORECAST AREA...WHICH SHOULD FURTHER INHIBIT LATE
DAY INSTABILITY. BETTER FORCING WILL ARRIVE IN THE FORM OF UPPER
LEVEL WIND DIVERGENCE AND DEEP LAYER DPVA TRAVERSING THE FORECAST
AREA CIRCA 00Z THIS EVENING. THIS FORCING WILL INTERACT WITH GREATER
MOISTURE IN SRN SECTIONS TO REQUIRE THE BEST CHC POPS THERE WITH THE
PASSAGE OF THE UPPER SUPPORT THIS EVENING...HOWEVER...THE MOST
RECENT CONVECTION ALLOWING MODELS HAVE DAMPENED EXPECTATION A BIT IN
THIS REGARD.

A SFC COLD FRONT WILL APPROACH FROM THE NW OVERNIGHT...BUT MAKE
LITTLE PROGRESS INTO THE REGION DURING THE MORNING HOURS. ABUNDANT
BOUNDARY LAYER MOISTURE WILL PERMIT A RETURN OF LOW CLOUDS...PERHAPS
A BIT LESS SOLID THAN THIS MORNING GIVEN THE DEVELOPING WEAK
WESTERLY DOWNSLOPE FLOW. MINS SHOULD BE COMPARABLE TO THIS MORNING.
THE FRONTAL BOUNDARY WILL THEN SLOWLY PUSH SE THROUGH THE REGION
THROUGH THE DAY ON TUE...PROVIDING ADDITIONAL TRIGGERING DURING THE
BEST HEATING PERIOD TUE AFTN. SB CAPE VALUES OF 1000 TO 1500 J/KG
ARE EXPECTED DURING THE AFTN HOURS AS THE WEAK DOWNSLOPE PROVIDES
FOR MORE SCATTERING. WIND SHEAR WILL NOT BE TERRIBLY
IMPRESSIVE...BUT SFC TO 3 KM VALUES COULD BUBBLE UP BRIEFLY TO 25 KT
ACROSS THE NRN TIER CIRCA 21Z. IN ADDITION...A POOL OF 6+ DEG C/KM
LAPSE RATES WILL PASS OVER THE AREA TO POSSIBLY ALLOW SOME TSRA TO
BECOME STRONG ALONG THE IMMEDIATE FRONT. THE CURRENT DAY 2 SPC
OUTLOOK HAS THE ENTIRE AREA IN A GENERAL TSTM RISK...AND THIS SEEMS
APPROPRIATE ALONG WITH A FEW STRONG CELLS POSSIBLE IN THE AFTN.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 215 PM MONDAY...A BROAD UPPER TROUGH WILL DOMINATE THE EASTERN
U.S. THROUGH THE SHORT TERM WITH A SERIES OF SHORT WAVES MOVING
THROUGH THE BASE OF THE TROUGH ACROSS SOUTHERN APPALACHIANS. THE
FIRST IN THE SERIES OF SHORT WAVES AND ASSOCIATED SURFACE COLD FRONT
WILL BE CROSSING THE AREA TUE EVENING. THE FRONT AT 00Z WED SHOULD
BE STRETCHED OUT ACROSS THE PIEDMONT AND IS FORECAST TO MOVE SE
OF THE AREA BY 06Z. SOME ASSOCIATED SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED AND THEY ALSO SHOULD MOVE OUT THE AREA BY
06Z. HIGH PRESSURE IS FORECAST TO BUILD SOUTH FROM THE OHIO VALLEY
IN THE WAKE OF THE FRONT BY WED MORNING. THE NAM IS MUCH DRIER
ACROSS THE REGION BEHIND THE FRONT THAN THE GFS AND THE NAM`S
ASSOCIATED QPF RESPONSE IS ALMOST NON-EXISTENT FOR WED. THE GFS
BOUNDARY LAYER WIND FLOW IS MORE NORTHEASTERLY AND SUBSEQUENTLY MORE
MOIST. THE GFS USES ANOTHER TRANSIENT UPPER SHORT WAVE TO TRIGGER
LIGHT QPF RESPONSE ACROSS MUCH OF THE AREA ON WED. USING A MODEL
CONSENSUS HIGHLIGHTS THE BLUE RIDGE ESCARPMENT WITH CHANCE POPS WITH
ONLY SLIGHT CHANCE ELSEWHERE. ANY PRECIP THAT DOES FALL WILL BE
LIGHT. BOTH THE GFS AND NAM AGREE THAT HIGH PRESSURE WILL REMAIN
NOSED INTO THE REGION THROUGH THU. THE MODELS FORECAST ESSENTIALLY
DRY CONDITIONS WITH ONLY ISOLATED SHOWERS AT BEST.

TEMPERATURES WILL BE ON THE COOL SIDE GENERALLY A COUPLE CATEGORIES
BELOW CLIMO FOR MAX TEMPS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MONDAY...HURRICANE ODILE WILL MOVE NE FROM ARIZONA
THURSDAY AND MERGE WITH A NORTHERN STREAM TROUGH OVER THE NATIONS
MID SECTION FRIDAY NIGHT AND SATURDAY. MEANWHILE...OUR COLD AIR
WEDGE INDUCED FROM THE SURFACE HIGH CENTERED OVER NEW ENGLAND FRIDAY
WILL GRADUALLY LOOSE ITS GRIP ON OUR WEATHER OVER THE WEEKEND. COOL
NE LOW LEVEL FLOW FROM THE NEW ENGLAND HIGH WILL SHIFT TO A
SOUTHERLY DIRECTION ON SUNDAY AS THE LOW PARTLY REMNANT TO ODILE
WILL CROSS THE GREAT LAKES SAT AND SAT NIGHT. THE BELOW NORMAL TEMPS
FRIDAY AND SATURDAY WILL BE GETTING CLOSER TO NORMAL SUNDAY AND
MONDAY AHEAD OF THE COLD FRONT CROSSING THE OHIO AND MISS VALLEY.
THIS COLD FRONT IS FORECAST TO REACH OUR REGION ON MONDAY PERHAPS
PRODUCING A FEW SHOWERS AND STORMS BUT WE ONLY HAVE SLIGHT CHANCE
POP AT THIS TIME FOR MONDAY. CAPES OF 500 TO 750 INDICATED ON THE
GFS MONDAY AFTERNOON AHEAD OF THE FRONT. VERY LITTLE FETCH OUT OF
THE GULF AHEAD OF THE FRONT AND NOT MUCH MOISTURE TO WORK WITH FOR
CONVECTION. DRYING OUT AND TURNING COOLER MONDAY NIGHT. WE START
NEXT WEEK WITH 500MB TROUGH OVER THE EAST AND A RIDGE OVER THE
WESTERN STATES.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...ANOTHER NIGHT...ANOTHER LESS-THAN-CONFIDENT FORECAST...
ALTHOUGH THE NEXT 6 HOURS APPEAR TO BE SLOWLY COMING INTO BETTER
FOCUS. IFR CIGS HAVE ALREADY BEEN OBSERVED EARLY THIS MORNING...AND
WITH PLENTY OF LOW LEVEL MOISTURE LINGERING...SEE NO REASON WHY THE
NEXT 6 HOURS SHOULD BRING ANY IMPROVEMENT TO THE TERMINAL. IN
FACT...CONDITIONS WILL PROBABLY GET A LITTLE WORSE BEFORE
DAYBREAK...AND EXPECT THE FLIGHT CATEGORY TO AT LEAST FLIRT WITH
LIFR CIGS PERIODICALLY. VISBY IS A BIT MORE UNCERTAIN...ESP WITH THE
WIDESPREAD CLOUD COVER ALREADY IN PLACE...BUT EXPECT VISBY TO
GENERALLY REMAIN IN THE MVFR RANGE...WITH PERIODS OF VFR AND IFR
POSSIBLE. THE GOOD NEWS IS THAT WITH INCREASING DOWNSLOPE FLOW
COMBINING WITH DAYTIME HEATING...CIGS ARE EXPECTED TO LIFT/SCATTER
RATHER QUICKLY AFTER SUNRISE...WITH VFR CONDITIONS LIKELY BY LATE
MORNING. THAT BEING SAID...MORE HEATING SPELLS MORE INSTABILITY AND
SCATTERED CONVECTION SHOULD DEVELOP ACROSS THE AREA DURING LATE
AFTERNOON/EARLY EVENING...WARRANTING A PROB30 FOR SHRA AFTER 22Z.

ELSEWHERE...GREENVILLE AND ASHEVILLE AREA TERMINALS HAVE ALREADY
BEEN BOUNCING IN AND OUT OF IFR/LIFR CONDITIONS THIS MORNING...AND
EXPECT THESE TO CONTINUE FOR THE BALANCE OF THE NEXT 4 HOURS OR SO.
SOME SHRA WILL ALSO BE POSSIBLE NEAR THE UPSTATE SC TERMINALS
THROUGH ABOUT 08Z...AS A SURFACE TROUGH MOVES THROUGH THE AREA.
SPEAKING OF WHICH...THE WINDS WILL SHIFT TO THE W/NW BEHIND THIS
TROUGH...WHICH IS THE PRIMARY REASON THAT FORECAST CONFIDENCE TANKS
AFTER 09-10Z...AS IT IS NOT OUT OF THE QUESTION THAT THIS DEVELOPING
DOWNSLOPE (UP-VALLEY AT KAVL) WIND COULD RESULT IN LIFTING CIGS
TOWARD DAYBREAK. WE HAVE THEREFORE FEATURED SLIGHT IMPROVEMENT AT
THESE TERMINALS BY 10Z...BUT AT LEAST A TEMPO FOR IFR WILL BE
CARRIED THROUGH 12Z. OTHERWISE...KAND/KHKY SHOULD EVENTUALLY SEE
PERIODS OF IFR/LIFR CONDITIONS THIS MORNING AS WELL. THE DOWNSLOPE
FLOW COMBINED WITH DAYTIME HEATING SHOULD RESULT IN CIGS LIFTING/
SCATTERING RATHER QUICKLY AFTER SUNRISE...WITH VFR CONDITIONS LIKELY
BY LATE MORNING. THAT BEING SAID...MORE HEATING SPELLS MORE
INSTABILITY AND SCATTERED CONVECTION SHOULD DEVELOP ACROSS THE AREA
DURING LATE AFTERNOON/EARLY EVENING...WARRANTING A PROB30 FOR TSRA
AT ALL TERMINALS BEGINNING AROUND 20Z GIVE OR TAKE.

OUTLOOK...A RETURN TO MAINLY VFR CONDITIONS IS EXPECTED TUE NIGHT
THROUGH MID WEEK. THE BEST CHANCE OF LOW CLOUDS EACH MORNING WILL BE
IN THE MOUNTAIN VALLEYS. ANOTHER ROUND OF COLD AIR DAMMING COULD
PRODUCE SOME FLIGHT RESTRICTIONS LATE THIS WEEK.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       MED   77%     HIGH  81%     HIGH 100%     HIGH 100%
KGSP       MED   74%     MED   68%     HIGH 100%     HIGH 100%
KAVL       MED   61%     MED   66%     HIGH 100%     LOW   58%
KHKY       MED   66%     MED   73%     HIGH 100%     HIGH 100%
KGMU       MED   70%     MED   75%     HIGH 100%     HIGH 100%
KAND       HIGH  80%     MED   78%     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...DEO
NEAR TERM...ARK/HG/JDL
SHORT TERM...LG
LONG TERM...DEO
AVIATION...JDL





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