Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291453
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1053 AM EDT FRI AUG 29 2014

.SYNOPSIS...
A COLD FRONT WILL LINGER OVER NORTH CAROLINA TODAY BEFORE
DISSIPATING TONIGHT. A BERMUDA HIGH WILL SET UP FOR THE WEEKEND AND
EARLY NEXT WEEK...BRINGING TYPICAL SUMMERTIME HEAT AND
HUMIDITY...WITH SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS EACH
DAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1015 AM UPDATE...STRATUS DECK HAS EXPANDED INTO THE NW NC PIEDMONT
WITHIN WEDGELIKE AIR MASS NORTH OF PESKY BACK DOOR FRONT. THE DECK/S
PROGRESS HAS SLOWED EVIDENTLY DUE TO MIXING ALONG THE EDGES AS
TEMPERATURES RISE. NONETHELESS IT STANDS A GOOD CHANCE OF LASTING
INTO MIDDAY DUE TO UPGLIDE ATOP THE COOLER LAYER. BIGGEST CHANGE TO
THE FCST AT THIS UPDATE WAS TO REFLECT THE MCLDY SKIES IN THIS AREA.
AS FOR POPS...MOST OF THE GUIDANCE DEVELOPS DEEP CONVECTION ONLY
OVER THE RIDGETOPS TODAY...DESPITE THE ELEVATED INSTABILITY SEEN
ABOVE THE STRATUS LAYER. THIS EVIDENCED BY RAP SOUNDINGS AS WELL AS
THE TOWERS SEEN EMBEDDED IN THE DECK ON SATELLITE OVER THE TRIAD
REGION. MAINTAINED SIMILAR POP TRENDS TO THOSE FROM EARLIER PACKAGE
BUT FOCUSED THEM MORE OVER THE NW NC PIEDMONT THIS MRNG FOR THE
LATTER REASON. NEWEST GUID ALSO ALLOWS SOME ELEVATED ACTIVITY TO
FIRE OVERNIGHT TONIGHT...BUT WITH THE WEDGE BEGINNING TO BREAK DOWN
BY THEN I WOULD LIKE TO SEE MORE OF A CONSENSUS BEFORE ADDING ANY
POPS FOR IT.

PREVIOUS DISCUSSION...
AS OF 330 AM EDT FRIDAY...UPPER LEVEL RIDGE CENTERED OVER THE
SOUTHEAST WILL CONTINUE TO DOMINATE THE PATTERN THROUGH THE NEAR
TERM FORECAST PERIOD.  MEANWHILE...DEEPENING SHORT WAVE TROF ACROSS
THE CENTRAL/SOUTHERN PLAINS CONTINUES TO PROMOTE PRESSURE FALLS AT
THE SURFACE LEADING TO STRONG MOISTURE ADVECTION ACROSS THE LOWER
MISSISSIPPI RIVER VALLEY.  ALSO AT THE SURFACE...QUASI STATIONARY
BACK DOOR FRONT REMAINS DRAPED IN AN EAST/WEST ORIENTATION ACROSS
NORTH CAROLINA...WEST INTO TENNESSEE.  A 1020MB SURFACE HIGH
ACROSS THE NORTHEAST CONTINUES SLIDE EAST AND WEDGE DOWN THE LEE
SIDE OF THE CENTRAL AND SOUTHERN APPS.

LATEST SATELLITE DIFFERENCE PRODUCT IMAGERY AND SURFACE OBS ANALYSIS
INDICATE AREA OF STRATUS DEVELOPMENT TIED TO A ZONE OF SURFACE
CONVERGENCE ALONG THE ABOVE MENTIONED BACK DOOR FRONT AND INTRUDING
SURFACE RIDGE.  GUIDANCE HAS HANDLED THIS SITUATION FAIRLY WELL
AND ALSO INDICATES FURTHER EXPANSION OF LOW STRATUS INTO THE
CENTRAL/SOUTHERN PIEDMONT REGION THROUGH LATE MORNING.
MEANWHILE...CALMING WINDS AND VERY MOIST DECOUPLING PBL ACROSS THE
HIGH TERRAIN WILL LEAD TO DEVELOPMENT OF PATCHY FOG THIS MORNING
WITH VISIBILITIES DROPPING TO LESS THAN 2 MILES...MAINLY IN AND
AROUND THE MOUNTAIN VALLEYS.  EXPECTING ABOVE MENTIONED HIGH
PRESSURE BOUNDARY AND OLD BACK DOOR FRONTAL BOUNDARY TO BE THE
PRIMARY FOCUS OF CONCERN THROUGH THE NEAR TERM PERIOD.  LOCATIONS
SOUTH OF THIS AXIS SUCH AS THE UPSTATE OF SOUTH CAROLINA AND
NORTHEAST GEORGIA WILL EXPERIENCE A FAIRLY NICE FRIDAY WITH MOSTLY
SUNNY SKIES AND DRY CONDITIONS PREVAILING AMONGST WEAK/INCREASING
SOUTHERLY FLOW AND UPPER LEVEL SUBSIDENCE.  AS FOR LOCATIONS TO THE
NORTH...SURFACE CONVERGENCE...BETTER MOISTURE PROFILES...AND WEAKER
CAPPING WILL WARRANT MENTION OF ISOLATED/SCATTERED SHOWERS AND
THUNDERSTORMS.  FORECAST SOUNDINGS DO INDICATE MODEST INSTABILITY
ACROSS THE SOUTHERN TIER OF WESTERN NORTH CAROLINA WERE BETTER
DIFFERENTIAL HEATING IS EXPECTED.  HOWEVER THIS THREAT SEEMS TO BE
TIED TO A RATHER SMALL AREA WERE ENOUGH INSTABILITY WILL EXIST
ADJACENT TO THE SURFACE CONVERGENCE AXIS PROVIDING NEEDED FORCING.

ALL SAID...THE HWO WILL MENTION LOW END THREAT FOR DIURNAL HEATING
AIDED ISOLATED THUNDERSTORMS ALONG THE I40 CORRIDOR WITH DAMAGING
WINDS AND FREQUENT LIGHTNING BEING THE PRIMARY THREATS.  CONVECTION
WILL TAPER INTO THE EARLY EVENING HOURS AS HEATING SUBSIDES WITH ALL
POPS BEING REMOVED BY MIDNIGHT.  TEMPERATURES ON FRIDAY WILL REACH
NORMAL LEVELS ACROSS MUCH OF THE UPSTATE AND NORTHEAST GEORGIA WITH
HIGHS BEING SLIGHTLY COOLER ACROSS WESTERN NORTH CAROLINA DUE TO SKY
COVER AND POSSIBLE CONVECTION.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 340 AM FRIDAY...UPPER ANTICYCLONE OVER THE SERN CONUS SLIDES
TO COAST SAT...THEN REMAINS THERE THRU THE PERIOD. THE ASSOCIATED
RIDGING REMAINS IN PLACE...BUT SLOWLY WEAKENS OR IS SUPPRESSED AS
NRN AND SRN STREAM SHORT WAVES MOVE EAST OVER AND INTO THE RIDGE. AT
THE SFC...SLY FLOW DEVELOPS AS A WEAK COLD FRONT MOVES TOWARD THE
AREA. THE FRONT WASHES OUT SUN...BUT SLY FLOW REMAINS AS A LEE TROF
DEVELOPS. WITH THE MOISTURE INCREASE...INSTABILITY DEVELOPS ACROSS
THE MTNS AND UPPER SAV RIVER VALLEY...LEADING TO SCT DIURNAL
CONVECTION. COULD SEE ISOLATED CONVECTION ACROSS THE FOOTHILLS AND
WRN UPSTATE IN THE TRANSITION ZONE BETWEEN AN UNSTABLE ATMOS AND A
CAPPED ATMOS OVER THE NC PIEDMONT AND ERN UPSTATE. TEMPS WILL BE
NEAR TO A LITTLE ABOVE NORMAL. MODERATE INSTABILITY DEVELOPS ACROSS
THE AREA SUN AS LOW LEVEL MOISTURE CONTINUES TO INCREASE. THE
WEAKENING BOUNDARY AND LEE TROF SHUD PROVIDE LOW LEVEL CONVERGENCE
WHILE THE SHORT WAVES AND UPPER DIVERGENCE FROM THE RIGHT ENTRANCE
REGION OF A JET STREAK PROVIDE SYNOPTIC SCALE FORCING. THE RESULT
WILL BE NUMEROUS COVERAGE OF DIURNAL CONVECTION ACROSS THE MTNS AND
SOLID SCT COVERAGE ALONG AND NORTH OF THE I-85 CORRIDOR...TAPERING
OFF SLIGHTLY TO THE SOUTH. PW VALUES INCREASE TO AROUND 2 INCHES
SUNDAY AND COULD LEAD TO STORMS WITH HEAVY RAINFALL...AND POSSIBLY
ISOLATED EXCESSIVE RAINFALL. HIGHS SUN WILL BE NEAR NORMAL WITH LOWS
SUN NITE A LITTLE ABOVE NORMAL.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 355 AM FRIDAY...THE UPPER ANTICYCLONE REMAINS SUPPRESSED OVER
THE SERN CONUS AT THE START OF THE PERIOD...THEN SLOWLY RETROGRADES
ACROSS THE GULF COAST STATES INTO THE MID SOUTH WITH RIDGING
BUILDING OVER THE MS RIVER VALLEY. NEARLY ZONAL FLOW ON TOP OF THE
ANTICYCLONE WILL BRING WEAK SHORT WAVES NEAR OR ACROSS THE AREA.

WEAK SLY LOW LEVEL FLOW AND A SFC LEE TROF REMAIN ACROSS THE AREA
THRU THE PERIOD. A COLD FRONT DOES DROP SOUTH TOWARD THE AREA WED...
BUT DISSIPATES BEFORE REACHING THE AREA. THIS WILL LEAD TO GENERALLY
SCT DIURNAL CONVECTION EACH DAY...WITH A RELATIVELY LULL ON TUE OF
LOW END SCT MTNS AND FOOTHILLS AND ISOLATED ELSEWHERE. HIGHS WILL BE
NEAR TO A LITTLE ABOVE NORMAL EACH DAY...WITH LOWS A LITTLE ABOVE
NORMAL THRU THE PERIOD.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AT KCLT...STATIONARY FRONTAL BOUNDARY WILL REMAIN IN THE AREA
THROUGH THE DAY BEFORE LIFTING NORTH OF THE AREA FRIDAY NIGHT INTO
SATURDAY MORNING. MVFR STRATUS DECK WILL LINGER IN THE AREA AS HIGH
PRESSURE WEDGES SOUTHWARD AND INTERACTS WITH ABOVE MENTIONED
BOUNDARY...BUT MIXING IS EXPECTED TO PREVENT IT FROM FORMING A CIG
AT THE FIELD EXCEPT MAYBE BRIEFLY. NORTHEAST WINDS WILL INCREASE
INTO THE 5-7KTS RANGE THROUGH MORNING BEFORE VEERING SOUTHERLY AS
THE BOUNDARY PUSHES NORTH LATE IN THE DAY OR EARLY EVENING. SOME LOW
END GUSTS ARE LIKELY AT TIMES THIS MORNING. CARRIED LIGHT
SOUTHEASTERLY WINDS UNDER LOW VFR CU FROM 00Z THROUGH THE REMAINDER
OF THE PERIOD.

ELSEWHERE...EXPECTING VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD
AT ALL SITES WITH THE POSSIBLE EXCEPTION OF FOG RESTRICITONS AT KAVL
SATURDAY MORNING. INITIALIZED ALL TAFS VFR WITH AN INTRODUCTION OF
MVFR LEVEL STRATUS AROUND 14Z AT KHKY AS MOISTURE CONDENSES ALONG
CONVERGENCE AXIS BETWEEN INTRUDING HIGH PRESSURE AND OLD STATIONARY
FRONT. VFR WILL RETURN TO ALL SITES BY MIDDAY WITH SKIES SCT OUT AND
WINDS SHIFTING SOUTHERLY AT THE SC SITES AND KAVL AS THE ABOVE
MENTIONED FRONT MIGRATES NORTH WHILE KHKY REMAINS NORTHERLY THROUGH
THE END OF THE PERIOD.

OUTLOOK...MOISTURE RETURN THROUGH THE WEEKEND WILL LEAD TO
INCREASING CHANCES FOR ISOLATED/SCATTERED DIURNAL SHRA AND TSRA WITH
THE GREATEST PROBABILITIES RESIDING ALONG THE HIGH TERRAIN. IN
ADDITION...MORNING FOG/STRATUS WILL BE POSSIBLE WITH THE MOUNTAINS
ONCE AGAIN HAVING THE GREATEST CHANCES AT RESTRICTIONS.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       MED   78%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     MED   65%     MED   65%
KHKY       MED   61%     HIGH 100%     MED   70%     MED   62%
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...WIMBERLEY
NEAR TERM...CDG/WIMBERLEY
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG/WIMBERLEY






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