Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 301045
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
645 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 /12Z TUESDAY THROUGH SATURDAY/...
AT KCLT...VFR FOR THE TIME BEING...BUT CONDITIONS ARE RIGHT FOR THE
FORMATION OF FOG IF THE HIGH BASED STRATOCU CEILING MOVES OFF TO THE
EAST...WHICH SHOULD HAPPEN IN THE PRE-DAWN HOURS. DENSE FOG HAS
ALREADY DEVELOPED ACROSS THE NW PIEDMONT TO SRN FOOTHILLS AND EXPECT
THE FOG AREA TO EXPAND S INTO METRO CLT THROUGH SUNRISE. WILL GO
MORE PESSIMISTIC THAN LAMP GUIDANCE AND INCLUDE A TEMPO FOR MVFR
VISIBILITY THROUGH 09Z...THEN PREVAILING MVFR WITH A TEMPO IFR FROM
09Z TO 13Z AS THE FOG EXPANDS. THIS COULD VERY EASILY GO TO LIFR OR
VLIFR IN THE 09Z TO 13Z TIME FRAME. THE FOG SHOULD LIFT AND
DISSIPATE BY 13Z OR SO...LEAVING BEHIND VFR CONDITIONS WITH ONLY A
FEW STRATOCU AND A LIGHT N WIND THROUGH THE REST OF THE PERIOD.

ELSEWHERE...WILL BE WATCHING FOR DENSE FOG DEVELOPMENT. THIS WAS
ALREADY MOST PREVALENT IN THE MTN VALLEYS WHERE CONDITIONS WILL BE
VARIABLE BETWEEN MVFR AND VLIFR THROUGH DAYBREAK. THE IFR HAD
ALREADY SURROUNDED KHKY AT ISSUANCE TIME AND SHOULD CLOSE IN BY 09Z.
THE OTHER TAF SITES GET A LONG TEMPO PERIOD FOR IFR VISIBILITY IN
FOG THROUGH DAYBREAK AT LEAST. THE FOG SHOULD LIFT AND DISSIPATE BY
MID MORNING AT THE VERY LATEST. AFTER THAT...VFR WITH LIGHT N WIND.
EXPECT MORE FOG TO START DEVELOPING IN THE MTN VALLEYS BY LATE
TUESDAY EVENING.

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.

CONFIDENCE TABLE...

            10-16Z        16-22Z        22-04Z        04-10Z
KCLT       HIGH  90%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   64%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   79%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       MED   73%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  83%     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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