Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 301719
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
119 PM EDT TUE SEP 30 2014

.SYNOPSIS...
DRIER HIGH PRESSURE WILL BUILD OVER THE REGION ON TODAY AND LINGER
THROUGH THURSDAY. A COLD FRONT WILL ARRIVE FROM THE NORTHWEST ON
FRIDAY WITH A COOL AND DRY AIR MASS MOVING BACK INTO THE REGION OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
1715 UPDATE...SKY COVER HAS BEEN ADJUSTED PER THE LATEST VISIBLE
SATELLITE IMAGERY. WINDS WERE UPDATED WITH A BLEND OF THE LATEST NAM
AND ADJMAV GUIDANCE.

AT 1000 AM EDT TUESDAY...AN UPPER TROUGH AXIS WAS LOCATED OVER THE
EASTERN SEABOARD...WITH ONE SHORTWAVE LEAVING THE COAST OF THE
CAROLINAS AND GA...AND ANOTHER MOVING INTO THE OH RIVER VALLEY. AN
UPPER LEVEL RIDGE AXIS WA MOVING FROM THE PLAINS TO THE MS RIVER
VALLEY. SURFACE FRONTS WERE LOCATED OVER THE NE GULF OF MEXICO...AND
THE OH RIVER VALLEY. SATELLITE IMAGERY SHOWED AREAS OF FOG ERODING
IN THE PIEDMONT...WHILE THE NC MOUNTAIN VALLEYS SHOWED LESS EROSION.

THE NORTHERN SHORTWAVE IS EXPECTED TO REACH THE NC MOUNTAINS BY LATE
THIS AFTERNOON...BUT THE SURFACE FRONT TO THE NORTH IS EXPECTED TO
STALL OVER WV AND KY. MODEL TIME HEIGHTS SHOW LIMITED LOW LEVEL
MOISTURE OVER OUR AREA. SOME SHALLOW INSTABILITY WILL EXIST BENEATH
A SUBSIDENCE INVERSION ALOFT...BUT CHANCES FOR PRECIPITATION REMAIN
QUITE LOW. HIGH TEMPERATURES WILL RUN SEVERAL DEGREES ABOVE NORMAL
IN UNDER SLOWLY RISING HEIGHTS ALOFT.

PREVIOUS DISCUSSION...A STRONG SHORT WAVE AND UPPER LOW DIVING DOWN
ACROSS THE GREAT LAKES TO THE UPPER OH VALLEY WILL KEEP AN UPPER
TROF AXIS ALONG THE E COAST THROUGH TONIGHT. THE PATTERN WILL
SUPPORT HIGH PRESSURE RIDGING DOWN FROM THE NW WITH DRY AIR
GRADUALLY FILTERING IN. FOR TONIGHT...THERE COULD BE MORE FOG
DEVELOPMENT...BUT MAINLY OVER THE MTNS. TEMPS WERE KEPT CLOSE TO AN
AVERAGE OF THE GUIDANCE...AND SLIGHTLY ABOVE NORMAL.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 310 AM TUESDAY...ON WEDNESDAY...A WEAK H5 RIDGE AXIS WILL
SLOWLY RIPPLE EAST ACROSS THE CWA. AT THE SFC...A WEAK LEE TROF IS
FORECAST TO DEVELOP DURING THE AFTERNOON...PROVIDING A WEAK PRESSURE
GRADIENT ACROSS THE SOUTHERN APPALACHIAN REGION. WINDS ARE EXPECTED
TO REMAIN AROUND 5 KTS FROM THE SFC UP TO H85. THE COMBINATION OF
MID LEVEL RIDGING AND WEAK FLOW ACROSS THE TERRAIN SHOULD FAVOR DRY
CONDITIONS FOR MOST OF THE CWA. HOWEVER...A SMALL POOL OF
INSTABILITY ACROSS THE WESTERN NC MTNS MAY SUPPORT ISO LATE
AFTERNOON SHRA...HIGHLIGHTED WITH SCHC POPS. TEMPERATURES ARE
FORECAST TO RANGE AROUND 5 DEGREES ABOVE NORMAL.

ON THURSDAY...CONDITIONS WILL CHANGE VERY LITTLE FROM WEDNESDAY.
HOWEVER...THE CENTER OF A LLVL RIDGE WILL SHIFT ALONG THE ATLANTIC
COAST THROUGH THE DAYLIGHT HOURS. AS A RESULT...LLVL WINDS ACROSS
THE CWA WILL STRENGTHEN SLIGHTLY FROM THE SOUTH...REACHING 15KTS AT
H85. THE SOUTH WINDS SHOULD ADVECT GULF MOISTURE ACROSS THE SOUTHERN
APPALACHIANS. DURING THE LATE AFTERNOON...WEAK SFC CAPE AND SSE FLOW
MAY SUPPORT A FEW SHRAS ACROSS THE MTNS. HIGH TEMPERATURES ARE
FORECAST TO RANGE FROM THE U70S WITHIN THE MTN VALLEYS TO LOW 80S
EAST.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 330 AM TUESDAY...MEDIUM RANGE MODELS TIME A SFC COLD FRONT AND
ASSOCIATED L/W TROF ACROSS THE CWA DURING THE DAYLIGHT HOURS FRIDAY.
0Z GFS DEPICTS THE CONCURRENCE OF SEVERAL INGREDIENTS ON FRIDAY TO
SUPPORT A PRE-FRONTAL BAND OF CONVECTION. BETWEEN SUNRISE AND MID
MORNING...A BAND OF H3 JET DIVERGENCE WILL TRACK OVERHEAD...RUNNING
AHEAD OF THE TROUGH AXIS. VEERING LLVL FLOW WILL INCREASE ACROSS THE
REGION AS THE COLD FRONT APPROACHES. DURING THE LATE
AFTERNOON...0-1KM HELICITY IS FORECAST TO RANGE FROM 150-200 M2/S2.
IN ADDITION...CAPE VALUES MAY RANGE FROM 500-1000 J/KG. THE FORECAST
ENVIRONMENT APPEARS FAVORABLE FOR A BAND OF CONVECTION TO DEVELOP
ALONG AND AHEAD OF THE COLD FRONT WEST OF THE MTNS EARLY FRIDAY
MORNING. THE BAND SHOULD SURVIVE THE PASSAGE ACROSS THE
MTNS...SUPPORTED BY A BROAD FIELD OF CAPE...UPPER FORCING...AND LLVL
SHEAR. I WILL FORECAST POPS TO RANGE FROM CATE TO LIKELY ON FRIDAY.
TEMPERATURES WILL BE LIMITED BY CLOUD COVER AND HIGH RAINFALL
COVERAGE...PEAKING AROUND 5 DEGREES BELOW NORMAL.

SATURDAY THROUGH MONDAY...HIGH PRESSURE WILL TRACK FROM THE
ROCKIES...ACROSS THE SOUTHERN MISSISSIPPI RIVER VALLEY...OFF THE
EAST COAST. THIS AIRMASS WILL FEATURE DRY AND COOL CONDITIONS. HIGH
PRESSURE CENTERED OVER THE CWA ON SUNDAY WILL RESULT IN THE COOLEST
TEMPS OF THE PERIOD. MORNING LOWS ON SUNDAY ARE FORECAST TO RANGE
FROM THE 40S ACROSS THE MTNS TO LOW 50 EAST...HIGHS AROUND 70.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
AT KCLT...MODEL TIME HEIGHTS SUGGEST THE PREDOMINANT CLOUD LAYER
WILL BE AROUND 4000 FT...BUT MOISTURE MAY BE TOO LIMITED TO SUPPORT
MORE THAN SCATTERED LOW CLOUDS...EVEN AT DAYBREAK. GUIDANCE SUPPORTS
ANOTHER ROUND OF DAYBREAK FOG HOWEVER. CONFIDENCE IS TOO LOW TO BUY
INTO IFR VSBY AT THIS TIME...SO MVFR WILL BE CARRIED. VFR RETURNS BY
MID MORNING. GENERALLY LIGHT SW WINDS ARE EXPECTED.

ELSEWHERE...CLOUD COVER MAY INCREASE WITH HEATING THIS AFTERNOON...
BUT NOT OF SUFFICIENT COVERAGE FOR A CIG. SOME LIMITED INSTABILITY
WIL BE PRESENT...BUT NOT OF A DEEP ENOUGH LAYER FOR CONVECTION...AND
RAIN CHANCES WILL BE TOO LOW TO MENTION. GUIDANCE SUPPORTS ANOTHER
ROUND OF FOG...BUT WITH CONFIDENCE LIMITED...ONLY IFR VSBY WILL BE
CARRIED AT KAVL AND KHKY...WITH MVFR AT KAND...AND VFR AT KGSP AND
KGMU. WINDS WILL GENERALLY FAVOR THE S OR SW AT FOOTHILLS SITE...AND
INITIALLY THE N AT KAVL BEFORE IT TOO SEES WINDS BACK TO THE S.

OUTLOOK...FOG/VSBY CONCERNS REMAIN THURSDAY. A FRONT WILL APPROACH
ON FRIDAY WHICH COULD TRIGGER SOME SHOWERS AND THUNDERSTORMS...WITH
ASSOCIATED RESTRICTIONS POSSIBLE. VFR RETURNS ON SATURDAY.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  94%
KGSP       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  94%
KAVL       MED   62%     LOW   55%     LOW   58%     LOW   57%
KHKY       HIGH 100%     HIGH  94%     HIGH  91%     HIGH  97%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  83%     HIGH  97%

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...NED
NEAR TERM...JAT/PM
SHORT TERM...NED
LONG TERM...NED
AVIATION...JAT





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