Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 152141
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
541 PM EDT MON SEP 15 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 TUESDAY/...
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 /TUESDAY NIGHT 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-EXISTANT 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 /22Z MONDAY THROUGH SATURDAY/...
AT KCLT...CIGS WILL ONLY SLOWLY IMPROVE THROUGH MVFR THROUGH THE
AFTN...LIKELY REACHING LOWER END VFR AFTER 20Z. WILL CONTINUE TO
FEATURE TEMPO SHRA FOR PRECIP DEVELOPMENT WITH A PASSING SHORTWAVE
TOWARD EVENING...BUT INSTABILITY STILL LOOKS LIMITED GIVEN THE
CONTINUED AFTN CLOUD COVER. AFTER A BRIEF BREAK IN THE LOWER
CIGS...MVFR CIGS WILL LIKELY FILL BACK IN OVERNIGHT GIVEN THE LOW
LEVEL MOISTURE...HOWEVER...WEAK WESTERLY DOWNSLOPE FROM THE MTNS
MAKES THIS A BIT LESS CERTAIN THROUGH TUE MORNING. WILL KEEP THE
FORECAST DRY THROUGH 18Z ON TUE WITH ACTIVATION ALONG THE FRONTAL
ZONE LIKELY DELAYED UNTIL LATER AFTN.

ELSEWHERE...PERSISTENT MVFR CIGS WILL CONTINUE TO BE SLOW TO SCATTER
THROUGH THE LATE AFTN HOURS. EXPECT THAT SHRA COVERAGE WILL RAMP UP
SLIGHTLY FROM THE WEST WITH AN APPROACHING SHORTWAVE 21Z TO 00Z THIS
EVENING...BUT WITH MOST SHOWERS DISSIPATING OVERNIGHT AS THE WAVE
MOVES EAST. THERE MAY BE JUST ENOUGH INSTABILITY FOR A FEW
TSRA...BUT ONLY KAND WILL GET A TEMPO FOR SLIGHTLY BETTER
INSTABILITY. THE LOWER MVFR CLOUDS WILL STEADILY FILL BACK IN
TONIGHT...BUT JUST AS IN THE CASE WITH KCLT...UNCERTAINTY ON THE LOW
DECK IS HIGH GIVEN A WEAK WESTERLY DOWNSLOPE FLOW THAT SETS UP. WILL
FEATURE PERSISTENCE INCLUDING IFR AT KAVL TOWARD DAYBREAK...MVFR AT
THE FOOTHILL SITES...AND THEN SLOW IMPROVEMENT THROUGH 18Z ON TUE.
WILL KEEP ANY PRECIP THREAT MENTION AFTER 18Z TUE ALONG THE
IMMEDIATE FRONTAL ZONE.

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...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH  89%     MED   70%     MED   61%     HIGH  92%
KGSP       HIGH  85%     MED   73%     LOW   53%     HIGH  90%
KAVL       HIGH  80%     MED   63%     MED   61%     MED   70%
KHKY       HIGH  88%     LOW   55%     LOW   50%     HIGH  90%
KGMU       HIGH  87%     MED   74%     MED   63%     HIGH  90%
KAND       HIGH  83%     MED   70%     LOW   57%     HIGH  90%

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
SHORT TERM...LG
LONG TERM...DEO
AVIATION...HG





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