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Area Forecast Discussion

609
FXUS62 KGSP 292339
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
739 PM EDT FRI AUG 29 2014

.SYNOPSIS...
A WEAK NEARLY STATIONARY FRONT WILL LINGER OVER NORTH CAROLINA
TONIGHT AND THEN DISSIPATE BY SATURDAY NIGHT.  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 SATURDAY/...
730 PM EDT UPDATE...CURRENT LAPS ANALYSIS SHOWS A MOIST SFC BNDRY
ACROSS THE SRN ZONES PROVIDING ENUF LIFT AND TD POOLING FOR ISOL
-SHRA TO DEVELOP. THESE CELLS WILL BE SHORT LIVED AND WILL LIKELY
NOT BECOME DEEP ENUF FOR A LIGHTNING CONCERN. TEMPS AND TD/S ARE IN
GOOD SHAPE AND ONLY MINOR ADJS WERE MADE TO SKY COVER ACROSS THE NRN
ZONES.

430 PM EDT UPDATE...THE FCST IS ON TRACK AND NEEDS ONLY MINOR
TWEAKS. MID LEVEL WARMING IS KEEPING CU FIELD IN CHECK WITH SOME
ENHANCEMENT SEEN ACROSS THE MTNS IN MECH LIFT. ISOLATED SHOWERS
WILL LIKELY FORM ACROSS THE RIDGETOPS OVER THE NEXT FEW HRS...BUT
MOST LOCALES WILL REMAIN DRY THROUGH THE AFTERNOON.

AS OF 130 PM EDT...LOW STRATUS ARE FINALLY DISSOLVING OVER OUR
PORTION OF THE NW NC PIEDMONT THOUGH OVC SKIES REMAIN JUST NE OF
CHARLOTTE. THESE CLOUDS ARE EXPECTED TO CONTINUE TO BREAK UP THROUGH
MID AFTERNOON. THE NEARLY STATIONARY BOUNDARY ON THE SRN FRINGE OF A
WEDGELIKE SFC RIDGE WHICH CAUSED THESE CLOUDS TO FORM EARLY THIS
MRNG REMAINS NEAR THE NC/SC BORDER. DEWPOINTS ARE CURRENTLY HIGHEST
IN AN ARC FROM ASHEVILLE TO SPARTANBURG TO CHARLOTTE...A RESULT OF
MOISTURE POOLING ALONG THE BOUNDARY. THIS HAS IMPLICATIONS FOR THE
FORECAST TONIGHT. HOWEVER...THOUGH ANALYZED CAPE VALUES ARE NOTABLY
HIGHER WITHIN THE AREA OF HIGHER DEWPOINTS...LOW TO MID LEVEL LAPSE
RATES ARE NOT GOOD ENOUGH EAST OF THE MTNS TO EXPECT DEEP
CONVECTION. HAVE MAINTAINED ISOLD TSRA MENTION OVER THE MTNS AND SRN
ESCARPMENT AREAS...BUT THAT/S IT.

TONIGHT THE UPPER RIDGE CONTINUES TO SHIFT EWD INTO CLASSIC BERMUDA
HIGH POSITION AS TROUGH MOVES INTO THE MISSISSIPPI VALLEY. ANY
REMNANT OF THE STATIONARY BOUNDARY APPEARS TO WASH OUT...AT LEAST
ENOUGH SO THAT ANY UPGLIDE WILL DIMINISH...SO LOW CLOUDS NOT
EXPECTED OVER THE BOUNDARY TONIGHT. VERY WEAK SOUTHERLY LLVL FLOW
WILL PREVAIL AGAIN OVER THE AREA WHICH DOES PROMPT THOUGHTS OF LOW
STRATUS OR FOG CREEPING UP FROM THE COAST...BUT MOISTURE DOES NOT
LOOK ESPECIALLY GOOD THIS FAR INLAND. A BETTER CASE CAN BE MADE FOR
FOG TO FORM WHERE SFC MOISTURE IS POOLING ALONG THE FRONT THIS
AFTN...GIVEN GOOD GUIDANCE SUPPORT FOR TEMPS COOLING BELOW THE
EXPECTED CROSSOVER TEMPS AS WELL AS WITH THE WEAK SOUTHERLY FLOW.
WILL ADVISE EVENING SHIFT TO CONSIDER THREAT OF PATCHY DENSE FOG
OVERNIGHT.

THAT UPPER TROUGH DOES BRING SOME WEAK DISTURBANCES NWD INTO THE
TENN VALLEY TOMORROW AFTN BUT THESE WILL HAVE MINIMAL IMPACT ON
FORCING OVER OUR AREA. LAPSE RATES AND MODEL CAPE VALUES ARE BEST
OVER THE SRN MTNS AND ADJACENT BLUE RIDGE...WHERE THE UPPER HEIGHTS
ARE A LITTLE LOWER. SOUTHERLY FLOW INTO THESE AREAS MAY ALSO ENHANCE
THE COVERAGE...SO I WILL MAINTAIN THE HIGHEST POPS THERE. FURTHER
EAST SUBSIDENCE CAPPING WILL KEEP THE FCST DRY. MAINLY DIURNAL
CUMULUS WILL BE SEEN FOR SKY COVER WITH MAX TEMPS NEAR NORMAL.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM FRIDAY...A WEAKENING SHORT WAVE TROUGH EJECTING FROM
THE GREAT PLAINS WILL ACT TO NUDGE THE SOUTHEAST CONUS UPPER HIGH
OFF THE SOUTHEAST COAST EARLY IN THE SHORT TERM...WHILE GENERALLY
RESULTING IN AN OVERALL LOWER AMPLITUDE UPPER PATTERN. A BERMUDA
HIGH WILL BECOME ESTABLISHED WITHIN THIS REGIME...WHICH WILL ACT TO
INCREASE MOISTURE AND INSTABILITY ACROSS THE WESTERN CAROLINAS AND
NORTH GEORGIA. ADDITIONALLY...A PLUME OF DEEP MOISTURE ACCOMPANYING
THE SHORT WAVE TROUGH/WEAKENING FRONTAL ZONE WILL APPROACH THE
FORECAST AREA BY SUNDAY MORNING. THIS SHOULD RESULT IN INCREASING
CHANCES FOR DEEP CONVECTION BEGINNING ACROSS THE WEST SUNDAY
NIGHT...WITH CHANCES INCREASING AND OVERSPREADING THE REMAINDER OF
THE AREA BY SUNDAY AFTERNOON. TERRAIN EFFECTS AND LEE TROUGH
INTERACTING WITH LINGERING MOISTURE PLUME...ALONG WITH RESPECTABLE
SBCAPE VALUES (GENERALLY 1500 TO 2500 J/KG PER FORECAST SOUNDINGS)
SHOULD SUPPORT SCATTERED TO PERHAPS NUMEROUS CONVECTION...WITH THE
HIGHEST POPS OCCURRING NEAR THE NC BLUE RIDGE. SHEAR WILL REMAIN
QUITE WEAK THROUGHOUT THE PERIOD...SO SEVERE STORM CHANCES WILL BE
LIMITED TO THE ISOLATED PULSE VARIETY.

WITH FRONTAL ZONE EXPECTED TO WEAKEN ACROSS THE EASTERN CONUS...
EXPECT A MORE TYPICAL DIURNAL WIDELY SCATTERED CONVECTIVE TREND TO
RETURN BY THE END OF THE PERIOD. THE BREAKDOWN OF THE RIDGE AND
INCREASING CLOUD COVER/CONVECTION SHOULD SPELL A PERIOD OF SLIGHTLY
BELOW NORMAL MAX TEMPS/NEAR NORMAL MINS THROUGH THE PERIOD.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 150 PM FRIDAY...THE MEDIUM RANGE PERIOD BEGINS 00Z TUESDAY
WITH A NEARLY ZONAL PATTERN ACROSS THE NATION AS AN UPPER RIDGE
DEPARTS EAST FROM THE ATLANTIC COAST. A SUBTROPICAL RIDGE BEING
SUPPRESSED SOUTH OVER FLORIDA AT 00Z TUES WILL RETROGRADE OVER THE
DEEP SOUTH BEING CENTERED OVER THE GULF STATES IN MID WEEK. THIS
RIDGE WILL EXPAND INTO LATE WEEK CREATING A GREATER AMPLITUDE
PATTERN THURS AND FRI WITH THE JET STREAM FROM CALIFORNIA TO THE
DAKOTAS TO NEW ENGLAND. THERE APPEARS TO BE A TREND IN THE
MODELS...ESPECIALLY IN THE GFS...OF MOVING THE CENTER OF THE RIDGE
EVEN FARTHER WEST AT THE END OF NEXT WEEK. IF THE CENTER OF THE
RIDGE SETS UP AROUND OKLAHOMA NEXT WEEKEND...OUR PATTERN MAY SHIFT
FROM BEING IN A RIDGE TO BEING IN NW FLOW WHICH WOULD BRING MCS
SYSTEMS FROM OVER THE TOP OF THE RIDGE TO THE CAROLINAS.

A WEAK COLD FRONT WILL DROP DOWN FROM THE NORTH IN MID WEEK BUT IT
IS QUESTIONABLE WHETHER THE FRONT WILL REACH OUR AREA BEFORE
DISSIPATING. THIS BOUNDARY WILL PROVIDE A FOCUS FOR CONVECTION IN
MID WEEK ESPECIALLY IN THE PM HOURS. LOW LEVEL WIND WILL BE LIGHT
AND VARY FROM DAY TO DAY DEPENDING ON THE INFLUENCES OF PASSING
SHORTWAVES TO THE NORTH...A PERSISTENT LEE TROUGH AND
WHETHER THE FRONT MAKES IT THROUGH OR NOT.

TEMPERATURES ARE FORECAST TO BE ABOVE NORMAL THROUGH THE PERIOD
UNDER THE UPPER RIDGE. MAXES ABOVE BY 5 TO 7 DEGREES IN MID WEEK AND
3 TO 5 ABOVE ON FRIDAY.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AT CLT...VFR CONDS THROUGH MOST OF THE OVERNIGHT WITH LIKELY MVFR
VSBY SETTING UP AFT 10Z THROUGH 13Z. BNDRY LAYER WINDS WILL MAINTAIN
A MOIST ATL FLOW AS WINDS VEER OVERNIGHT AND THIS COULD ALSO SUPPORT
LOW STCU. THE RAP SOUNDINGS INDICATE MORE OF A FG/BR THREAT THAN
CIGS AS DOES THE STAT GUIDANCE...SO WILL GIVE MORE WEIGHT TO THE
MVFR VSBY. THE CURRENT P/GRAD RIDGE BECOMES MERIDIONALLY ALIGNED
SAT...WHICH WILL SUPPORT SSE/LY FLOW THRU THE AFTERNOON.

ELSEWHERE...THE SC SITES WILL REMAIN VFR OVERNIGHT AS SOUNDINGS
INDICATE DRY LLVLS AND TDDS ABOVE 2 C...HOWEVER A BNDRY SOUTH MAY
SUPPORT MFVR VSBY AFT 10Z AT KAND. THERE COULD BE SOME MVFR LEVEL
STCU DEVELOPING AFT 09Z OR SO...BUT THE OVERALL AVAIL MOISTURE
SHOULD BE TOO LOW FOR CIGS. AT KAVL...VSBYS SHOULD START DROPPING
AFT 05Z AND BECOME IFR BTW 09Z/12Z AS DRYING ALOFT DEVELOPS OVER A
SHALLOW MOIST LAYER. VISIBILITIES AT KHKY WILL ALSO DROP
OVERNIGHT...BUT PROBABLY REMAIN IN THE MVFR RANGE WITH A RELATIVELY
DRYER SFC LAYER THAN THE MTN VALLEYS.

OUTLOOK...MOISTURE RETURN BEGINNING SAT NIGHT 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...

            23-05Z        05-11Z        11-17Z        17-23Z
KCLT       HIGH 100%     HIGH 100%     HIGH  94%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH  97%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  94%     HIGH 100%
KHKY       HIGH 100%     HIGH  80%     HIGH  97%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  88%     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...DEO
NEAR TERM...SBK/WIMBERLEY
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...SBK






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