Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 310740
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
340 AM EDT SUN AUG 31 2014

.SYNOPSIS...
A BERMUDA HIGH WILL DEVELOP AND LINGER THROUGH EARLY IN THE WEEK...
RESULTING IN TYPICAL SUMMERTIME HEAT AND ISOLATED TO SCATTERED
AFTERNOON THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 325 AM EDT SUNDAY...UPPER LEVEL TROF TO THE WEST WILL CONTINUE
TO DOMINATE THE PATTERN THROUGH THE NEAR TERM FORECAST PERIOD.
LIKEWISE...ELONGATING UPPER RIDGE AND SURFACE HIGH PRESSURE OFF THE
MID ATLANTIC COAST WILL CONTRIBUTE TO INCREASING SOUTHERLY FLOW.
UPPER TROF ENERGY REMAINS THE DOMINANT FORCING MECHANISM THIS
MORNING AS BAND OF CONVECTION CONTINUES TO PUSH EAST OUT OF
NORTHEAST GA INTO WESTERN NC AND THE UPSTATE.  DESPITE LIMITED
INSTABILITY PRESENT ACROSS THE REGION...UPPER ENERGY AND SURFACE
MOISTURE ADVECTION HAVE LED TO MODERATELY DEEP UPDRAFTS SUPPORTIVE
OF PRONOUNCED RAIN RATES.  OBSERVATIONS FROM AROUND THE REGION HAVE
INDICATED THAT SOME OF THE HEAVIER CELLS ARE YIELDING APPROXIMATELY
ONE INCH PER HOUR RATES.  THAT SAID...FORWARD PROPAGATION COMBINED
WITH ANTECEDENT DRY CONDITIONS WILL INHIBIT ANY FLOODING THREATS
THIS MORNING.  LATEST MODEL GUIDANCE SOLUTIONS TO INCLUDE CAMS
INDICATE THAT THIS BAND OF CONVECTION WILL WEAKEN TOWARDS DAYBREAK
AS IT PUSHES UP INTERSTATE 85 TOWARDS THE NC PIEDMONT.  THEREFORE
THE FORECAST FEATURES NUMEROUS SHOWERS/THUNDERSTORMS ACROSS THE NC
FOOTHILLS SOUTHWARD INTO THE UPSTATE WITH ISOLATED SHOWERS POSSIBLE
AFTER DAYBREAK ACROSS THE EAST.  ALTHOUGH TEMPERATURES WILL BE SLOW
TO COOL BENEATH CLOUDY SKIES...EXPECTING INCREASED BOUNDARY LAYER
MOISTURE FROM CONVECTION TO AID IN PATCHY FOG ACROSS THE REGION.
FORTUNATELY 5-10MPH WINDS WILL LIKELY INHIBIT DEVELOPMENT OF
WIDESPREAD/DENSE FOG.

CONDITIONS WILL IMPROVE ACROSS THE REGION BY LATE MORNING WITH LOW
LEVEL STRATUS LINGERING LEADING TO MOSTLY CLOUDY SKIES.  THIS SKY
COVER IS EXPECTED TO SCATTER OUT WITH MIXING AS THE ATMOSPHERE
BEGINS TO HEAT.  MEANWHILE...ANOTHER UPPER SHORT WAVE WILL APPROACH
FROM THE WEST PROVIDING NEEDED SUPPORT FOR CONVECTION DURING THE
AFTERNOON HOURS.  UPPER LEVEL AND SURFACE RIDGE WILL REMAIN NEARLY
STATIONARY ACROSS THE SOUTHEAST WITH THE MAJORITY OF THE FORECAST
AREA RESIDING ON THE PERIPHERY.  AS A RESULT...FORECAST SOUNDINGS
ARE MODERATELY UNSTABLE WITH WEAK LOW/MID LEVEL INHIBITION WORKING
TO LIMIT CONVECTION.  EXPECTING ABOVE MENTIONED UPPER WAVE ENERGY
SLIDING EAST TO AID CONVECTION...ESPECIALLY ACROSS THE HIGH TERRAIN
WHERE CAPPING WILL BE WEAKEST.  THEREFORE POPS WILL INCREASE TO
SLIGHT CHANCE LEVELS ALONG THE INTERSTATE 85 CORRIDOR WITH SOLID
CHANCE LEVEL POPS FURTHER WEST ALONG THE MOUNTAINS.  POPS WILL TAPER
DOWN INTO THE EVENING HOURS AS THE UPPER TROF AND ASSOCIATED ENERGY
EJECT TO THE NORTHEAST AND DIURNAL COOLING COMMENCES.  IN GENERAL
TEMPERATURES THROUGH THE PERIOD WILL REMAIN AT OR JUST ABOVE NORMAL
LEVELS WITH SOME DEVIATION POSSIBLE DEPENDING ON LONGEVITY AND
COVERAGE OF CONVECTION/CLOUDS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 205 AM SUNDAY...UPPER SUBTROPICAL ANTICYCLONE WILL REMAIN OVER
THE SERN CONUS THRU THE PERIOD WHILE A LOW AMPLITUDE UPPER TROF
MOVES EAST IN THE WRLY FLOW ACROSS THE NRN CONUS. AT THE SFC...A
BERMUDA HIGH REMAINS OVER THE SERN CONUS KEEPING TYPICAL SUMMERTIME
PATTERN ACROSS THE AREA MONDAY AND TUE. A WARM HUMID AIR MASS WITH A
LEE TROF REMAINS IN PLACE THRU THE PERIOD HELPING PRODUCE A TYPICAL
PATTERN OF DIURNAL CONVECTION WITH SCATTERED COVERAGE OVER THE MTNS
AND ISOLATED COVERAGE ELSEHWERE. A FLY IN THE OINTMENT TO THIS
SCENARIO IS A WEAK COLD FRONT THAT DROPS TOWARD THE AREA TUE NITE
AHEAD OF THE AFORE MENTIONED UPPER TROF. THIS COULD KEEP CONVECTION
GOING THRU THE NITE...ESPECIALLY ACROSS THE NC MTNS. HIGHS WILL
REMAIN NEARLY STEADY ABOVE NORMAL EACH DAY...WHILE ABOVE NORMAL LOWS
MON NITE RISE A COUPLE OF DEGREES TUE NITE.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 335 AM SUNDAY...GUIDANCE IN GOOD AGREEMENT THRU THU. THE UPPER
ANTICYCLONE REASSERTS ITSELF ACROSS THE SERN CONUS AS AN UPPER TROF
MOVES EAST OF THE AREA. SOME WEAK SHORT WAVE ENERGY IS STILL ABLE TO
MOVE ACROSS THE AREA THRU THE RIDGING. AT THE SFC...A WEAK COLD
FRONT DRIVEN BY THE DEPARTING TROF MOVES INTO THE AREA AND STALLS.
EVEN THO THE FRONT WASHES OUT...A LOW LEVEL CONVERGENCE BOUNDARY
REMAINS IN PLACE. THIS LEADS TO SCT MAINLY DIURNAL CONVECTION WED
AND THU. THE LATEST GFS SHOWS THE RIDGE RETROGRADING ALLOWING SHORT
WAVES TO DROP ACROSS THE AREA FRI AND SAT IN THE DEVELOPING WEAK
NWLY FLOW. THE ECMWF KEEPS THE RIDGE IN PLACE FRI...THEN WEAKENS IT
AND SUPPRESSES IT TOWARD THE GULF COAST SAT. HOWEVER...THE RIDGE IS
STILL STRONG ENUF TO KEEP ANY SHORT WAVES AND WLY FLOW NORTH OF THE
AREA. EVEN WITH THE UPPER AIR DIFFERENCES...THE SFC FEATURES ARE
REMARKABLY SIMILAR. THE WEAK SFC BOUNDARY HOLDS ON FOR ONE MORE DAY
FRI LEADING TO ANOTHER ROUND OF MAINLY DIURNAL SCT CONVECTION. THE
GFS THEN BRINGS A COLD FRONT INTO THE AREA SAT WHILE THE ECMWF
BRINGS IT TOWARD...BUT NOT QUITE INTO THE CWFA. GIVEN THE
DIFFERENCES...HAVE KEPT PRECIP AS SCT MAINLY DIURNAL CONVECTION.
ABOVE NORMAL HIGHS WED DROP TO NEAR NORMAL FOR FRI AND SAT...WHILE
LOWS BOUNCE AROUND ABOVE NORMAL THRU THE PERIOD.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL INITIALLY AHEAD OF POSSIBLE
VISB REDUCTIONS NEAR DAYBREAK.  INITIALIZED TAF VFR WITH 07KT
SOUTHERLY WINDS UNDER SCT LOW VFR STRATOCU.  INTRODUCED 2HR TEMPO AT
11Z TO ACCOUNT FOR DECOUPLING PBL AND POTENTIAL MVFR LEVEL FOG
RESTRICTIONS.  BY 13Z CONDITIONS WILL IMPROVE UNDER BKN/OVC LOW
LEVEL STRATUS LASTING THROUGH MUCH OF THE MORNING BEFORE LOW LEVEL
MOISTURE MIXES OUT.  BY MIDDAY...SKIES WILL FEATURE SCT MID/HIGH
LEVEL CLOUDS WITH INCREASING SOUTHERLY WINDS FOR THE REMAINDER OF
THE PERIOD.  AS FOR WX...CURRENT RADAR TRENDS AND LATEST CAM
GUIDANCE INDICATE BAND OF CONVECTION ACROSS NORTHEAST GA WILL NOT
SURVIVE THE TRIP EAST INTO THE NC PIEDMONT...THEREFORE NO WX MENTION
FOR THIS FEATURE.  HOWEVER...AS THE PROFILE HEATS DURING THE
AFTERNOON HOURS ON SUNDAY CANNOT RULE OUT SHRA/TSRA LATE IN THE DAY
THEREFORE KEPT PREVIOUS PROB30 FOR SUCH.

ELSEWHERE...A MIXTURE OF VFR/MVFR AND POSSIBLE IFR CONDITIONS WILL
BE POSSIBLE THROUGH THE EVENING AT ALL SITES.  ABOVE MENTIONED BAND
OF CONVECTION WILL SPREAD EAST AFFECTING THE SC SITES ALONG WITH
KAVL THROUGH THE OVERNIGHT.  THEREFORE EACH TAF LOCATION FEATURES
PREVAILING VCTS LEADING UP TO ARRIVAL WITH A TEMPO FOR TSRA AND IFR
CIGS/VISB DURING PASSAGE.  CONDITIONS WILL SLOWLY IMPROVE AFTER
DAYBREAK AT ALL SITES AS ABOVE MENTIONED SHRA/TSRA ERODES ALONG WITH
INCREASING CLOUD BASES.  VFR WILL PREVAIL LATE IN THE PERIOD WITH
THE EXCEPTION OF PROB30 MENTION AT KAVL AND KHKY TO ACCOUNT FOR
AFTERNOON CONVECTION.  WINDS THROUGH THE PERIOD WILL REMAIN
SOUTHERLY WITH FLOW INCREASING INTO SUNDAY AFTERNOON.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH EARLY NEXT
WEEK WITH THE EXCEPTION FOR RESTRICTIONS IN THE EARLY MORNING DUE TO
LOW CLOUDS AND FOG...PRIMARILY IN THE MOUNTAIN VALLEYS. DIURNAL
CONVECTION IS EXPECTED EACH AFTERNOON WITH THE MOST COVERAGE OVER
THE MOUNTAINS.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       MED   60%     MED   79%     HIGH 100%     HIGH 100%
KAVL       HIGH  80%     HIGH  93%     HIGH 100%     HIGH 100%
KHKY       HIGH  82%     HIGH  94%     HIGH 100%     HIGH 100%
KGMU       MED   66%     MED   74%     HIGH 100%     HIGH 100%
KAND       MED   69%     MED   79%     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...RWH
NEAR TERM...CDG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG






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