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Area Forecast Discussion

857
FXUS62 KGSP 311847
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
247 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 MONDAY/...
AS OF 230 PM EDT...BERMUDA HIGH WILL REMAIN STRONG THROUGH TONIGHT
AND MONDAY...THOUGH NUMEROUS MESOSCALE UPPER DISTURBANCES WILL PASS
BY ON ITS NW FRINGE AS THEY EXIT THE CENTRAL CONUS TROUGH. THESE
DISTURBANCES LARGELY SHOULD LEAVE OUR CWFA UNSCATHED AS THEY PASS
BY...WITH THE NRN MTNS MOST LIKELY TO SEE AN IMPACT ON CONVECTIVE
COVERAGE. UNDER THE RIDGE...LAPSE RATES WILL REMAIN MARGINAL FOR
DEEP CONVECTION WITH SOME DEGREE OF MIDLEVEL CAPPING THIS AFTN AND
AGAIN MONDAY AFTN. ONCE AGAIN...PROFILES WILL REMAIN SLIGHTLY MORE
FAVORABLE OVER THE MTNS BEING MORE UNDER THE INFLUENCE OF THE UPPER
TROUGH. IN SHORT...NEAR TO SLIGHTLY BELOW CLIMO POPS ARE EXPECTED
THIS AFTN AS WELL AS MONDAY AFTN. A PASSING VORT MAX THIS EVENING
MIGHT ALLOW CONVECTION TO CONTINUE NEAR THE TENN BORDER PAST THE END
OF HEATING...BUT ELSEWHERE THE FCST IS DRY FOR TONIGHT.

DESPITE THE AFOREMENTIONED LIMITATIONS SEEN WITH PROFILES...IF ANY
CELLS DO KICK OFF THEY WILL BE CAPABLE OF VERY HIGH RAINFALL RATES
OWING TO THE PWAT VALUES WELL ABOVE CLIMO...IN EXCESS OF 1.6 INCHES
ACRS MOST OF THE AREA. DCAPE VALUES ARE NOT ESPECIALLY HIGH GIVEN
ALL THE MOISTURE...BUT ARE PERHAPS SLIGHTLY HIGHER THAN ON AVERAGE.
SPC HAS ISSUED AN MCD FOR THE UPPER TENN VALLEY AND SURROUNDING
AREAS INCLUDING THE WNC MTNS TO HIGHLIGHT AN ISOLD MICROBURST
THREAT. IT DOES SEEM THIS CAN/T BE RULED OUT...BUT THE BETTER CASE
CAN BE MADE WEST OF THE MTNS WHERE THERE IS BETTER UPPER FLOW
BENEATH THE TROUGH.

SKY COVER IS A TOUGH CALL FOR TONIGHT BUT IT APPEARS THERE IS LITTLE
SUPPORT FOR WIDESPREAD LOW CLOUDS. PATCHY MID-HIGH CLOUDS ARE LIKELY
HOWEVER. DEWPOINTS AND CROSSOVER TEMPS ARE BOTH HIGH DUE TO THE
MOIST LLVL CONDITIONS. FAVORING LIGHTER MOS WINDS...PATCHY FOG IS
LIKELY ACRS MUCH OF THE REGION DESPITE LIMITED COOLING ON ACCOUNT OF
THE MOIST CONDITIONS. TEMPS WILL BOTTOM OUT A COUPLE DEGREES ABOVE
NORMAL. MORE MIXING IS EXPECTED TOMORROW SO RH SHOULD BE A LITTLE
MORE TOLERABLE...WITH HIGHS A LITTLE ABOVE NORMAL.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM SATURDAY...TYPICAL LATE SUMMER WEATHER IS EXPECTED
THROUGH THE SHORT TERM...AS SUBTROPICAL/BERMUDA HIGH PRESSURE
GENERALLY MAINTAINS ITS HOLD ACROSS THE SOUTHEAST. A SHORT WAVE
TROUGH PASSING NORTH OF OUR REGION LATE TUE. ASSOCIATED COLD FRONT
WILL APPROACH THE SOUTHERN APPALACHIANS FROM THE TENN VALLEY TUE
EVENING... POSSIBLY ENHANCING CONVECTIVE CHANCES ACROSS THE NC MTNS
DURING THIS TIME. HOWEVER...WITH THE PRIMARY SYNOPTIC SCALE FORCING
PASSING BY TO OUR NORTH...WEAK SHEAR...AND WEAKENING INSTABILITY
ASSOCIATED WITH THE NOCTURNAL COOLING CYCLE...IT/S NOT CLEAR HOW
LONG INTO TUE NIGHT CONVECTION WILL CONTINUE BEFORE DISSIPATING.
CHANCE POPS HAVE GENERALLY BEE LIMITED TO THE EVENING HOURS.

THE FRONT IS EXPECTED TO INTRODUCE A SLIGHTLY COOLER/SLIGHT DRIER
AIR MASS TO THE AREA...WITH TEMPS EXPECTED TO TOP OUT CLOSER TO
CLIMO FOR WED AFTERNOON. IT DOES NOT APPEAR THAT ANY DRYING WILL BE
SUBSTANTIAL ENOUGH TO PRECLUDE AFTERNOON DESTABILIZATION AND DIURNAL
CONVECTIVE DEVELOPMENT. NEAR-CLIMO POPS (LOW CHANCE MTNS/SLIGHT
CHANCE EAST) WILL BE ADVERTISED WED AFTERNOON.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM EDT SUNDAY...LATEST GLOBAL MODELS HAVE TRENDED WEAKER
UPPER RIDGING ACROSS THE SOUTHERN CONUS...LEADING TO INCREASING
CHANCES FOR CONVECTION THROUGHOUT THE MEDIUM RANGE PERIOD. WED NIGHT
THRU FRI...MODELS STILL DEPICT UPPER RIDGING AMPLIFYING ACROSS THE
REGION THRU THU...THEN WEAKENS BY FRI IN RESPONSE TO A NORTHERN
UPPER TROUGH TRAVERSING THE UPPER MIDWEST. A FRONTAL BOUNDARY JUST
TO OUR SOUTH WILL BE WASHED OUT BY THURSDAY AS A BERMUDA HIGH
RE-BUILDS ACROSS THE SOUTHEAST AND REMAIN IN PLACE THRU FRI. DESPITE
THE UPPER RIDGING ALOFT...ATLANTIC MOISTURE INFLUX AND MODERATE
DIURNAL BUOYANCY (1500-2500J/KG SBCAPE) WILL BE SUPPORTIVE OF
SCATTERED CONVECTION. HENCE...HAVE UPDATED POPS TO INCREASE TO
AROUND 40-50 RANGE. SAT AND SUNDAY...THE UPPER RIDGE FLATTENS OUT
OVER THE SOUTHEAST AS THE UPPER TROUGH MOVES ACROSS THE GREAT LAKES
REGION SAT AND INTO THE OHIO VALLEY BY SUN. THIS WILL ALLOW COOLER
SURFACE HIGH TO SLIDE SOUTH...PUSHING A BACK DOOR COLD FRONT THROUGH
THE FORECAST AREA BY SAT NIGHT/EARLY SUN. WITH GOOD LLVL
CONVERGENCE...UPPER DPVA...MOIST PROFILE AND MODERATE
INSTABILITY...WE SHOULD SEE RATHER ACTIVE WEATHER PATTERN WITH HEAVY
RAINFALL BEING THE PRIMARY THREAT ATT. TEMPS WILL BE AROUND 2-3
DEGREES ABOVE NORMAL THURSDAY AND NEAR NORMAL FRI INTO SUN.

&&

.AVIATION /19Z 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...JOH
NEAR TERM...WIMBERLEY
SHORT TERM...JDL
LONG TERM...JOH
AVIATION...WIMBERLEY






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