Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 311816
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
216 PM EDT SUN AUG 31 2014

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

&&

.NEAR TERM /THROUGH TONIGHT/...
130 PM UPDATE...VIRTUALLY ALL OF THE LOW CLOUDS HAVE ERODED OVER THE
CWFA BUT DIURNAL CU ARE NOW FILLING IN ACRS SOME AREAS. IT APPEARS
THE CAPPING AND MARGINALLY POOR LAPSE RATES ASSOCIATED WITH THE
BERMUDA HIGH ARE WORKING TO INHIBIT DEEP CONVECTION ACRS THE AREA
WITH CU LOOKING SHALLOW FOR THE MOST PART. SUFFICIENT
DESTABILIZATION IS EXPECTED BY MID AFTN TO ALLOW MENTIONABLE POPS
EVERYWHERE AT THAT TIME...THOUGH MINIMAL OVER THE PIEDMONT.

PREVIOUS DISCUSSION...

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 SUNDAY/...
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 /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT...MVFR LEVEL CU DECK SHOULD LIFT BEFORE FORMING A CIG IF IT
FORMS A CIG AT ALL TODAY. WINDS WILL BE SOMEWHAT VARIABLE DUE TO
DIFFERENTIAL HEATING IN/AROUND CLOUDY PATCHES...BUT BY MID AFTN THEY
SHOULD PREVAIL SSW. A COUPLE SHOWERS MIGHT POP NEARBY BUT WITH
LARGELY UNFAVORABLE PROFILES FOR CONVECTION...CHANCE AT THE FIELD
TOO LOW TO MENTION IN TAF. HUMID AFTN CONDITIONS WILL KEEP CROSSOVER
TEMPS SUFFICIENTLY HIGH FOR A FOG RISK EARLY MONDAY...THOUGH MVFR IS
EXPECTED AT WORST. WINDS SHOULD COME UP FROM THE WSW MONDAY MRNG.

ELSEWHERE...BERMUDA HIGH WILL PRODUCE UNFAVORABLE LAPSE RATES AND
MINIMIZE DIURNAL SHRA/TSRA ACRS THE PIEDMONT...BUT SCT CELLS WILL BE
ABLE TO DEVELOP IN THE MTNS ALONG THE FRINGE OF THE HIGH. VCTS
MENTION AT KAVL. CLOUD BASES WILL BE NEAR 030 EARLY THIS AFTN BUT
LIFT AS THE DAY GOES ON. CIGS UNLIKELY OVER THE TAF TERMINALS THRU
THE NIGHT. MTN VALLEYS HOWEVER ARE EXPECTED TO SEE IFR VSBY DEVELOP
IN FOG TOWARD DAWN...PERHAPS BRINGING CIGS THERE. MVFR FOG POSSIBLE
ELSEWHERE DUE TO CONTINUED MOIST CONDITIONS AND LIMITED MIXING THIS
AFTN KEEPING CROSSOVER TEMPS HIGH. MAINLY SWLY WINDS ACRS THE AREA
THRU THE PERIOD...BUT PERIODS OF VARIABILITY LIKELY AT KAVL DUE TO
VALLEY EFFECTS IN THIS FLOW.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE
WEEK...BUT RESTRICTIONS ARE POSSIBLE EARLY EACH MORNING DUE TO LOW
CLOUDS AND FOG...PRIMARILY IN THE MOUNTAIN VALLEYS. DIURNALLY DRIVEN
SHRA/TSRA ARE EXPECTED EACH AFTERNOON WITH THE MOST COVERAGE OVER
THE MOUNTAINS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  92%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH  95%     HIGH  91%
KAVL       HIGH 100%     HIGH  95%     HIGH  82%     HIGH  95%
KHKY       HIGH 100%     HIGH 100%     HIGH  95%     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...RWH
NEAR TERM...CDG/WIMBERLEY
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...WIMBERLEY






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