Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 151754
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
154 PM EDT MON SEP 15 2014

.SYNOPSIS...
COOL BUT UNSETTLED WEATHER WILL CONTINUE THROUGH TONIGHT...AS A
STATIONARY FRONT WILL REMAIN JUST TO OUR SOUTH BEFORE AN UPPER
DISTURBANCE PASSES THROUGH. A COLD FRONT WILL THEN CROSS THE AREA IN
ITS WAKE...USHERING IN SEASONABLY COOL AIR AND MOSTLY DRY WEATHER
LASTING INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 145 PM EDT...RADARS ARE FAIRLY QUIET ACROSS THE FORECAST AREA
THIS AFTN AS A FAIRLY STABLE SHALLOW COOL SFC LAYER REMAINS IN PLACE
ACROSS THE REGION. ALOFT...WATER VAPOR IMAGERY SHOWS A SRN STREAM
SHORTWAVE MOVING INTO WRN TN EARLY THIS AFTN. IR IMAGERY SHOWS THAT
MID AND HIGH CLOUDS ARE INCREASING AHEAD OF THIS FEATURE ATOP THE
LOWER CLOUDS ALREADY IN PLACE...WHICH SHOULD FURTHER INHIBIT LATE
DAY INSTABILITY. BETTER FORCING SHOULD ARRIVE...HOWEVER...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 BETTER MOISTURE IN SRN SECTIONS TO REQUIRE THE BEST CHC POPS
THERE WITH THE PASSAGE OF THE UPPER SUPPORT THIS EVENING.

A SFC COLD FRONT WILL APPROACH FROM THE NW OVERNIGHT...BUT MAKE
LITTLE PROGRESS INTO THE REGION DURING THE MORNING HOURS. BOUNDARY
LAYER MOISTURE WILL PERMIT A RETURN OF LOW CLOUDS...BUT 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
THROUGHOUT THE DAY ON TUE...PROVIDING ADDITIONAL TRIGGERING DURING
THE BEST HEATING PERIOD TUE AFTN. SB CAPE VALUES OF 1000 TO 2000
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 ALLOW SOME TSRA TO BECOME
STRONG ALONG THE IMMEDIATE FRONT. THE NEW DAY 2 SPC HAS PLACED 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 CROSS THE AREA TUE EVENING. THE FRONT AT 00Z SHOULD BE
STRETCHED OUT ACROSS THE PIEDMONT AND SHOULD 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 INT HE WAKE
OF THE FRONT BY WED MORNING. THE NAM IS MUCH DRIER ACROSS THE REGION
BEHIND TH FRONT THAN THE GFS AND ITS ASSOCIATED QPF RESPONSE IS
ALMOST NON-EXISTANT. THE GFS BOUNDARY LAYER WIND FLOW IS MORE
NORTHEASTERLY AND SUBSEQUENTLY MORE MOIST. THE GFS USES ANOTHER
TRANSIETN UPPER SHORT WAVE TO TRIGGER LIGHT QPF RESPONSE ACROSS MUCH
OF THE AREA. USING A MODEL BLEND HIGHLIGHTS THE BLUE RIDGE
ESCARPMENT WITH CHANCE POPS WITH ONLY SLIGHT CHANCE ELSEWHERE. ANY
PRECIP THAT DOEMS FALL WILL BE LIGHT. BOTH THE GFS AND NAM AGREE
THAT HIGH PRESSURE WIL REMAIN NOSED INTO THE REGION THROUGH THU. THE
MODELS FORECAST ESSENTIALLY DRY CONDITIONS WITH ONLY ISIOLATED
SHOWERS AT BEST.

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

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
AS OF 230 AM MONDAY...AN INITIALLY SIMPLE WESTERN RIDGE/EASTERN
TROUGH PATTERN THURSDAY WILL BECOME MORE COMPLEX OVER THE WEEKEND
WITH REASONABLE AGREEMENT BETWEEN THE 15/00Z GFS AND 14/12Z EC AS TO
ITS EVOLUTION. THE ERN TROUGH PROGRESSES ENOUGH TO ALLOW REAL COLD
AIR DAMMING TO FORM BY FRI MRNG...REINFORCING SEASONABLY COOL TEMPS
FOR THE REGION AND SUPPORTING A DRY FCST THRU MOST OF THE WEEKEND.
WEAK UPPER RIDGING RETURNS TO THE SOUTHEAST SATURDAY AS THE PARENT
HIGH IS PUSHED OFFSHORE. THIS IN CONJUNCTION WITH LOW PRESSURE
MOVING ALONG THE CANADIAN BORDER INITIATES RETURN FLOW
SUNDAY...WEAKENING THE WEDGE AND ALLOWING A BRIEF WARMUP. THAT LOW
DOES THEN BRING ANOTHER COLD FRONT INTO OUR AREA TO START THE NEW
WEEK. GFS IS MORE BULLISH WITH THE FRONT AS IT DEVELOPS A SECONDARY
SFC LOW OVER THE MIDWEST IN RESPONSE TO A SHORTWAVE EMBEDDED IN THE
SYNOPTIC FLOW. THE 15/00Z EC JUST ARRIVED STILL FAVORING THE
PREVIOUS RUN/S TRACK OF THE CANADIAN LOW...BUT AMPLIFIES THE UPPER
TROUGH SUBSTANTIALLY. THIS BACKS UP A STRONGER FROPA FOR EARLY
MONDAY. EITHER WAY IT LOOKS LIKE EVEN COOLER WEATHER IS IN STORE
NEXT WEEK.

&&

.AVIATION /18Z 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
DAYTIME 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
FROM THE WEST WITH AN APPROACHING SHORTWAVE 21Z TO 00Z THIS
EVENING...WITH MOST SHOWERS DISSIPATING OVERNIGHT. 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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  85%     MED   78%     MED   69%     MED   71%
KGSP       MED   72%     MED   79%     MED   62%     MED   68%
KAVL       MED   78%     MED   64%     MED   64%     LOW   57%
KHKY       HIGH  89%     MED   72%     LOW   49%     MED   65%
KGMU       HIGH  81%     MED   79%     MED   70%     MED   75%
KAND       HIGH  80%     MED   77%     MED   69%     MED   68%

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...WIMBERLEY
NEAR TERM...HG
SHORT TERM...LG
LONG TERM...WIMBERLEY
AVIATION...HG





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