Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 301055
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
655 AM EDT THU JUL 30 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE INTO THE REGION FROM THE NORTHWEST
TODAY AND SETTLE SOUTHEAST OF THE AREA TONIGHT THROUGH FRIDAY. THE
FRONT AND ASSOCIATED DEEPER MOISTURE WILL LIKELY REMAIN CONFINED
ALONG THE SOUTHEAST COASTLINE THROUGH THE WEEKEND...WITH SLIGHTLY
COOLER TEMPERATURES AND MUCH DRIER AIR EXPECTED OVER THE FORECAST
AREA. LOW LEVEL MOISTURE WILL GRADUALLY RETURN EARLY NEXT WEEK AS
ANOTHER COLD FRONT APPROACHES FROM THE NORTH.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 650 AM...THE FORECAST APPEARS IN GOOD SHAPE. I WILL TAYLOR
POPS TO REFLECT LIGHT RETURNS OVER THE WESTERN NC MTNS. IN
ADDITION...I WILL REDUCE FOG MENTION.

AS OF 345 AM...LATEST SFC ANALYSIS INDICATED THAT A COLD FRONT WAS
CROSSING MIDDLE KY AND TN...MOVING EAST. BASED ON RECENT OBSERVATION
TRENDS AND MODEL GUIDANCE...THE COLD FRONT IS EXPECTED TO SWEEP
ACROSS THE SOUTHERN APPALACHIANS AROUND MID DAY...REACHING THE
PIEDMONT LATE THIS AFTERNOON/EARLY EVENING. MOS GUIDANCE INDICATES
THAT HIGH TEMPERATURES SHOULD RANGE IN THE MID 80S WITHIN THE MTN
VALLEYS TO LOW TO MID 90S EAST. SFC DEWPOINTS ARE FORECAST TO REMAIN
BETWEEN 66 TO 71 DEGREES DURING THE HEAT OF THE AFTERNOON. MODEL
SOUNDINGS AND PLAIN VIEW SHOW CAPES GENERALLY RANGING NEAR 2000
J/KG. NAM AND RAP DCAPE INCREASE TO VALUES GREATER THAN 1000 J/KG
ALONG AND AHEAD OF THE FRONT. BASED ON THE NAM...A BROKEN BAND OF
TSRA SHOULD DEVELOP ALONG AND AHEAD OF THE FRONT. THE CONVECTION MAY
CROSS THE MTNS DURING THE MORNING DAYLIGHT HOURS...SLIDING ACROSS
THE PIEDMONT DURING THE EARLY TO MID AFTERNOON. IN THE WAKE OF THE
BAND...SCT DISCRETE CELLS MAY DEVELOP...MOVING EAST BY SUNSET. GIVEN
THE MODERATE CAPE...A WIDE FIELD OF DCAPE...AND THE DAYTIME PASSAGE
OF A COLD FRONT...IT APPEARS THAT SEVERAL STORMS COULD PRODUCE
DAMAGING WIND GUSTS. HAIL IS POSSIBLE...BUT HIGH WBZ SHOULD LIMIT
HAIL SIZE TO LESS THAN SEVERE. WE WILL HIGHLIGHT THE SEVERE
POTENTIAL IN THE HWO.

TONIGHT...WEAK CAA AND FALLING DEWPOINTS WILL INCREASE FROM NW TO SE
IN THE WAKE OF THE FRONT. SKY COVER SHOULD CLEAR FROM WEST TO
EAST...WITH MOST OF THE AREA UNDER LITTLE CLOUD COVER BY DAWN
FRIDAY. GIVEN THE LIGHT NNW WINDS...THE COOLEST THICKNESSES SHOULD
REMAIN OVER THE MTNS. I WILL FORECAST LOWS IN THE 50S AND 60S ACROSS
THE MTNS...WITH LOW 70S EAST.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 330 AM EDT THURSDAY...A BROAD EASTERN TROUGH WILL DEVELOP ON
FRIDAY. UNDER THIS TROUGH...DRIER AIR WILL SPILL INTO THE REGION
FROM THE NORTH AS A DEPARTING SFC FRONT SETTLES TO THE SOUTHEAST
COAST AND SURFACE HIGH PRESSURE STRETCHES FROM THE MID MS RIVER
VALLEY TO THE SRN AND CENTRAL APPALACHIANS. DEWPOINTS
ADVECTING/MIXING WELL DOWN IN THE 50S IN MOST AREAS WILL LARGELY
PRECLUDE ANY CONVECTION ON FRIDAY...WITH ANY ISOLD SHOWERS CONFINED
TO THE EXTREME LOWER PIEDMONT DURING THE AFTERNOON HOURS.

THE EASTERN TROUGH WILL AMPLIFY OVER THE WEEKEND AS A SERIES OF
SHORTWAVES MOVE THROUGH THE MEAN TROUGH AXIS. DRY SFC HIGH PRESSURE
WILL REMAIN IN PLACE ON SATURDAY...WITH A WEAKLY REINFORCING SURFACE
FRONT APPROACHING FROM THE NORTH LATE IN THE DAY. ISOLATED SHOWER OR
WEAK TSTM COVERAGE MAY OCCUR LATE DAY JUST N OF THE REGION ALONG THE
FRONT AND ALSO ACROSS THE SOUTHERN TIER WHERE DEWPOINTS MAY RECOVER
EVER SO SLIGHTLY.

THE AIRMASS WILL CONTINUE TO MODIFY ON SUNDAY...BUT WITH MOISTURE
VERY SLOW TO RETURN. THE SHORTWAVES MOVING THROUGH THE ERN TROUGH
WILL REMAIN DIFFICULT TO TIME...BUT THERE IS DEVELOPING CONSENSUS ON
STRONGER Q VECTOR CONVERGENCE WITH A SHORTWAVE LATE SUNDAY INTO
SUNDAY NIGHT JUST AS MOISTURE REBOUNDS SLIGHTLY. THIS WILL WARRANT
BETTER ISOLD COVERAGE OF SHRA/TSRA LATE SUNDAY...WITH MORE OF A NON
DIURNAL ISOLD NIGHTTIME POP MENTION ON SUNDAY NIGHT. TEMPERATURES
WILL REMAIN NEAR TO SLIGHTLY ABOVE CLIMO THROUGH THE PERIOD.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 330 AM EDT THURSDAY...MODEL CONSENSUS DEPICTS SLIGHT
SHALLOWING OF THE ERN TROUGH MONDAY THROUGH WEDNESDAY. MEANWHILE...
A MORE VIGOROUS SURFACE COLD FRONT WILL MOVE SOUTH OF THE GREAT
LAKES ON MONDAY AND APPROACH THE FORECAST AREA FROM THE NORTH ON
TUESDAY. THERE IS CONSIDERABLE MEDIUM RANGE MODEL SPREAD ON HOW FAR
SOUTH THE FRONT GETS...WITH THE ECMWF GENERALLY STALLING THE
BOUNDARY N OF THE AREA...WHILE THE GFS AND ASSOCIATED ENSEMBLES
BRING IT AT LEAST INTO THE NRN TIER BEFORE TURNING IT AROUND AS A
WARM FRONT ON WEDNESDAY. A CONSENSUS APPROACH WILL KEEP THE BOUNDARY
N OF THE AREA BUT FEATURE AN UPTICK IN DIURNAL AFTN CONVECTIVE
COVERAGE AHEAD OF THE FRONT AS THE BOUNDARY LAYER CONTINUES TO
REBOUND AND LAPSE RATES FURTHER STEEPEN ALOFT. TEMPERATURES WILL
GRADUALLY WARM THROUGH THE PERIOD.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AT KCLT...THE PRIMARY FORECAST CHALLENGE WILL BE THE TIMING OF A
SWEEPING COLD FRONT AND ASSOCIATED WIND SHIFT. AT 10Z...THE COLD
FRONT WAS ANALYZED OVER MIDDLE KY/TN. THE COLD FRONT IS FORECAST TO
SWEEP EAST TODAY...REACHING THE NC PIEDMONT LATE THIS AFTERNOON. I
WILL FORECAST LIGHT SW WINDS ACROSS THE CLT TERMINAL THROUGH THE
MORNING HOURS...VEERING WNW BY 17Z. A BROKEN BAND OF SHRA/TSRA WILL
LIKELY FORM AHEAD OF THE FRONT...TRACKING SE. BASED ON THE 6Z
NAM...THE MOST LIKELY TIME WINDOW FOR CONVECTION SHOULD OCCUR
BETWEEN 19Z TO 22Z...HIGHLIGHTED WITH A TEMPO. IN THE WAKE OF THE
FRONT...NNW WINDS SHOULD STRENGTHEN TO 5 TO 10KTS WITH VFR
OVERNIGHT CONDITIONS.

ELSEWHERE...SUNRISE TEMPERATURES HAVE CLOSED IN ON CROSSOVER VALUES
YIELDING LIGHT FOG AT KGSP AND KGMU. KAVL HAS SEEN SOME VLIFR CLOUDS
THIS MORNING...BUT LATEST OBS INDICATE THAT THESE CEILINGS HAVE
DISSIPATED. I WILL LIMIT SKY TO SCT003 IN THE INITIAL LINE OF THE
KAVL TAF...WILL MONITOR CLOSELY THIS MORNING. PRE FRONTAL CONVECTION
SHOULD FORM AHEAD OF THE COLD FRONT...WITH COVERAGE INCREASING AS IT
MOVES EAST. I WILL USE A TEMPO FOR EACH SITE EAST OF THE MTNS
     INDICATING A EARLY TO MID AFTERNOON BAND OF TSRA. AFTER THE
CONVECTION...WINDS SHOULD VEER NNW AND REMAIN THROUGH THE REST OF
THE TAF PERIOD.

OUTLOOK...HIGH PRESSURE WITH BUILD IN BEHIND A PASSING COLD FRONT
LATE ON THURSDAY ALLOWING FOR GENERALLY DRY AND QUIET WEATHER
THROUGH THE WEEKEND.  CHANCES FOR SHOWERS/THUNDERSTORMS AND THUS
RESTRICTIONS WILL RETURN FOR THE START OF THE NEW WORK WEEK.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   31%     HIGH 100%     HIGH 100%     LOW   58%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     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...NONE.
SC...NONE.

&&

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



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