Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 301119
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
719 AM 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/...
AS OF 630 AM...A LARGE AREA OF DENSE FOG PERSISTED ACROSS THE
WESTERN CAROLINAS GENERALLY E OF THE BLUE RIDGE. THE DENSE FOG AREA
HAS DEVELOPED ACROSS MOST OF UPSTATE SC...SO THE DENSE FOG ADVISORY
HAS BEEN EXPANDED TO INCLUDE THOSE AREAS. MEANWHILE...THE FOG HAS
ALREADY LIFTED TO PATCHY LOW STRATUS ACROSS THE FRENCH BROAD
VALLEY...PARTLY IN RESPONSE TO SOME DRIER AIR FILTERING UP THE
VALLEY FROM THE NW. WILL CANCEL THE ADVISORY EARLY FOR THE NC MTNS.
THE FOG SHOULD DISSIPATE FAIRLY QUICKLY AFTER SUNRISE WITHOUT MUCH
IN THE WAY OF CLOUDS ABOVE THE LOW STRATUS TO DELAY ANY WARMUP.

THE NEXT 24 HOURS SHOULD BE RELATIVELY QUIET. 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. A MOSTLY CHANNELED VORT MAX WILL MOVE OVERHEAD TODAY WITH
LITTLE TO SHOW FOR IT BECAUSE OF A LACK OF MOISTURE. THE PATTERN
WILL SUPPORT HIGH PRESSURE RIDGING DOWN FROM THE NW WITH DRY AIR
GRADUALLY FILTERING IN. THE NAM SUGGESTS THE DEVELOPMENT OF A FEW
SHOWERS NEAR THE BLUE RIDGE THIS AFTERNOON BECAUSE OF MOISTURE
CONVERGENCE...BUT FCST SOUNDINGS SHOW A VERY SHALLOW LAYER OF
INSTABILITY BELOW A STRONG SUBSIDENCE INVERSION. WILL NOT INCLUDE
ANY SHOWERS AT THIS TIME AS THE GFS IS NOT AS EXCITED. FOR
TONIGHT...THERE COULD BE MORE FOG DEVELOPMENT...BUT MAINLY OVER THE
MTNS. TEMPS WERE KEPT CLOSE TO AN AVERAGE OF THE GUIDANCE.

&&

.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 /11Z TUESDAY THROUGH SATURDAY/...
AT KCLT...CONDITIONAL CLIMATOLOGY SUGGESTS THAT VLIFR CONDITIONS DUE
TO DENSE FOG WILL CONTINUE UNTIL ABOUT 13Z...AFTER WHICH EXPECT A
PERIOD OF VSBY IMPROVING TO MVFR...THEN VFR BY AROUND 14Z OR PERHAPS
15Z AT THE VERY LATEST AS THERE IS NO MID/HIGH CLOUD LAYER TO
PREVENT A QUICK WARMUP. THE REST OF THE DAY SHOULD BE VFR WITH A FEW
STRATOCU AND A LIGHT N WIND. LATE TONIGHT...FOG IS POSSIBLE ONCE
AGAIN...SO AN MVFR VSBY WAS INCLUDED AFTER 10Z...BUT CONFIDENCE NOT
AS HIGH AS IT WAS FOR FOG THIS MORNING.

ELSEWHERE...VARIABLE VISIBILITY FIRST THING THIS MORNING AT TAF
SITES OUTSIDE THE MTNS...BUT GENERALLY IN THE VLIFR TO IFR RANGES.
PLACES THAT DO NOT HAVE THE DENSE FOG WILL PROBABLY HAVE VERY LOW
STRATUS...AND THUS WILL BE AT LEAST IFR AS WELL. THE FOG/STRATUS IS
EXPECTED TO BURN OFF BY 14Z AT MOST PLACES. THEREAFTER...VFR WITH A
LIGHT N WIND. EXPECT MORE FOG DURING THE EARLY MORNING HOURS ON
WEDNESDAY WITH MOST PLACES AT LEAST MVFR. THE MOUNTAIN VALLEYS HAVE
THE BEST CHANCE OF DROPPING TO IFR.

OUTLOOK...VFR CONDITIONS WILL PREVAIL WED THROUGH FRIDAY MORNING...
WITH FOG/VSBY CONCERNS REMAINING ACROSS THE MTNS AND FOOTHILLS EARLY
EACH MORNING. A FRONT WILL APPROACH ON FRIDAY WHICH COULD TRIGGER
SOME SHOWERS AND THUNDERSTORMS...WITH ASSOCIATED RESTRICTIONS
POSSIBLE. EXPECT VFR TO RETURN ON SATURDAY.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z
KCLT       MED   75%     HIGH 100%     HIGH 100%     HIGH  86%
KGSP       HIGH  86%     HIGH 100%     HIGH 100%     HIGH  91%
KAVL       HIGH  88%     HIGH 100%     HIGH 100%     HIGH  94%
KHKY       HIGH  81%     HIGH 100%     HIGH  94%     HIGH 100%
KGMU       HIGH  82%     HIGH 100%     HIGH 100%     HIGH  91%
KAND       MED   72%     HIGH 100%     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...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR NCZ035>037-
     056-057-068>072-082-501>510.
SC...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR SCZ001>014-
     019.

&&

$$
SYNOPSIS...NED
NEAR TERM...PM
SHORT TERM...NED
LONG TERM...NED
AVIATION...PM





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