Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291806
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
206 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/...
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 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 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 /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT/KHKY/KAVL/KGSP...VFR SHOULD PREVAIL INTO THIS EVENING...BUT
A FEW PATCHES OF MVFR LEVEL STRATUS WILL LINGER NEARBY EARLY THIS
AFTN OVER THE PIEDMONT. WEAK BUT PERSISTENT STATIONARY FRONT NEAR
NC/SC BORDER WILL POOL MOISTURE THIS AFTN AND KEEP DEWPOINTS FROM
MIXING OUT APPRECIABLY. GIVEN THE EXPECTED CALM AND FEW-SCT SKY
COVER TONIGHT...RADIATIONAL COOLING SHOULD ALLOW TEMPS TO EASILY
APPROACH CROSSOVER VALUES. KAVL HAS THE BEST SUPPORT FROM GUIDANCE
FOR DENSE FOG SO HAVE PREVAILED LIFR AROUND DAYBREAK THERE. I THINK
THE OTHER SITES HAVE A BETTER SHOT AT MIXING OUT SOME LATER
TODAY...PLUS THERE ARE MIXED SIGNALS FROM GUID. THUS ONLY IFR TEMPOS
THERE. EXCEPT AT KAVL WHICH IS ALREADY SELY...THE OTHER SITES WILL
FLIRT WITH ESE WINDS LATER THIS AFTN BEFORE GOING CALM
OVERNIGHT...THEN COME UP FROM THE SE SATURDAY.

AT KGMU/KAND...EXPECTING VFR TO PREVAIL THIS PERIOD...THOUGH KGMU
WILL BE NEARER THE AREA OF BETTER MOISTURE DESCRIBED ABOVE AND HENCE
HAS A SMALL CHANCE OF A RESTRICTION AROUND DAYBREAK. WINDS WILL
MAINLY STAY E TO SE THIS AFTN...GOING CALM BY EVENING...AND
PREVAILING SELY AGAIN SATURDAY.

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%
KHKY       MED   71%     HIGH 100%     HIGH  87%     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...DEO
NEAR TERM...WIMBERLEY
SHORT TERM...RWH
LONG TERM...DEO
AVIATION...WIMBERLEY




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