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Area Forecast Discussion

770
FXUS62 KGSP 281808
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
208 PM EDT THU AUG 28 2014

.SYNOPSIS...
A COLD FRONT WILL DROP DOWN INTO NORTH CAROLINA FROM THE NORTH
TONIGHT...LINGERING OVER THE REGION BRIEFLY BEFORE MOVING BACK
NORTH ON FRIDAY. 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 FRIDAY/...
AS OF 145 PM EDT...SKIES REMAIN CLEAR OVER MOST OF THE AREA THOUGH
RIDGETOPS ARE STARTING TO CLOUD UP DUE TO DIURNAL CUMULUS. BACK DOOR
COLD FRONT REMAINS DIFFICULT TO PICK OUT...THOUGH BASED ON LLVL WIND
AND THERMAL FIELDS IT APPEARS TO EXTEND FROM UPPER EAST TN INTO THE
VA PIEDMONT...JUST NORTH OF OUR AREA. SOME SHOWERS ARE POPPING OVER
THE CUMBERLAND PLATEAU IN AN AREA OF MUCH GREATER INSTABILITY THAN
SHOWN FURTHER EAST. NONETHELESS SOME WEAK FORCING IS OCCURRING AS
EVIDENCED BY THE CU FIELD SEEN ALONG THE BOUNDARY. LLVL PROGS STILL
SUGGEST THE FRONT WILL REMAIN STATIONARY BEFORE DRIFTING SWD INTO NC
TONIGHT. SO FOR THE REST OF THE AFTN SFC HEATING WILL HAVE TO
SUFFICE FOR ANY PRECIP TO FORM IN OUR ZONES. CONVECTION ALLOWING
MODELS FOCUS ON THE RIDGETOPS...WHICH WITH MINIMAL STEERING FLOW ARE
THE ONLY AREAS THE CONSENSUS SUGGESTS QPF. DID ALLOW SOME ISOLD POPS
TO EXTEND INTO THE ADJACENT FOOTHILLS MAINLY NORTH OF I-40. NOT
ESPECIALLY EXCITED ABOUT THE SEVERE POTENTIAL WITH DCAPES OF ONLY
500-700...AND UPDRAFTS LIMITED BY MEDIOCRE LAPSE RATES. NONETHELESS
WE ARE STILL IN THE 5 PERCENT WIND THREAT AREA ON THE SPC DAY 1
OUTLOOK. WE WILL HOWEVER MONITOR ANY DEVELOPING CELLS CLOSELY.

MORE DETAILS TO COME SHORTLY.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 200 PM THURSDAY...A PRONOUNCED UPPER HIGH WILL REMAIN OVER THE
SE STATES THEROUGH SATURDAY WHICH WILL TEND TO LIMIT CONVECTIVE
CHANCES THE FIRST PART OF THE LONG LABOR DAY WEEKEND AS MID LEVEL
LAPSE RATES WILL BE WEAK. HOWEVER...BY LATE IN THE DAY ON SATURDAY
WITH UPSLOPE FLOW AND INCREASING MOISTURE FLUX CAN`T RULE OUT SOME
SCT SHOWERS/STORMS OVER THE MOUNTAINS/NE GA AND THE WESTERN UPSTATE.
ON SUNDAY...THE AXIS OF THE RIDGE IS FORECAST TO SHIFT EASTWARD. AT
THE SAME TIME...THE GFS BRINGS SOME VORT ENERGY NORTHEASTWARD
ASSOCIATED ORIGINALLY WITH THE WEAK TROPICAL DISTURBANCE CURRENTLY
OVER THE NORTHERN GULF. THE MOISTURE INFLUX AND DPVA SHOULD PROVIDE
THE IMPETUS FOR NUMEROUS SHOWERS/STORMS OVER THE MOUNTAINS SUNDAY
AFTERNOON...WITH AT LEAST SCT COVERAGE EAST OF THE MOUNTAINS. IT
APPEARS THAT LOCALLY HEAVY RAIN WILL BE THE PRIMARY THREAT ON SUNDAY
WITH DEEP LAYER MOISTURE AND PW`S AROUND 2 INCHES. TEMPS WILL BE A
CATEGORY OR SO ABOVE NORMAL IN THE MOUNTAINS ON SAT...AND A COUPLE
DEGREES ABOVE CLIMO ELSEWHERE. TEMPS ARE FORECAST TO RETURN TO NEAR
CLIMO ON SUNDAY WITH INCREASED CLOUD COVER AND AFTERNOON
CONVECTION.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AT 200 PM EDT THURSDAY...A FLAT UPPER RIDGE WILL BE OVER THE
SOUTHERN TIER OF STATES ON MONDAY...WHILE A LOW AMPLITUDE TROUGH
REMAINS OVER THE NORTHERN PLAINS. THE RIDGE BUILDS SLOWLY NORTH AS
THE UPPER TROUGH DEAMPLIFIES. BY THURSDAY THE RIDGE CENTER MOVES
INTO THE TN RIVER VALLEY AS A NEW TROUGH AMPLIFIES ALONG THE WEST
COAST.

THE WESTERN EDGE OF A BERMUDA HIGH WILL EXTEND OVER THE CAROLINAS
AND GA ON MONDAY...WITH THE BULK OF GULF INFLOW TO THE WEST OVER THE
LOWER MS RIVER VALLEY. GULF INFLOW WEAKENS ON TUESDAY AS THE
PRESSURE GRADIENT OVER THE WESTERN GULF RELAXES...WHILE A COLD FRONT
DROPS INTO THE OH RIVER VALLEY FORM THE NW. THIS FRONT MOVES INTO
OUR AREA ON WEDNESDAY...MOVING JUST SOUTH OF OUR AREA BY EARLY
THURSDAY.

PRECIPITATION WILL INITIALLY BE DRIVEN BY MOIST UPSLOPE FLOW FORM
THE SOUTH....FOCUSING MAINLY ON THE SOUTH FACING BLUE RIDGE
ESCARPMENT. A RELATIVE LULL IN PRECIPITATION CAN BE EXPECTED AS
SOUTHERLY MOIST INFLOW DECREASES TOWARD MID WEEK....FOLLOWED BY
INCREASING CHANCES OF PRECIPITATION WITH THE ARRIVAL OF THE FRONT.
TEMPERATURES WILL START OUT ABOVE NORMAL UNDER THE UPPER RIDGE...BUT
WILL EXHIBIT A REDUCED DIURNAL RANGE WITH THE ARRIVAL OF CLOUDS AND
MOISTURE ASSOCIATED WITH THE FRONT.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...WINDS WILL REMAIN SOMEWHAT VARIABLE BUT SHOULD PREVAIL
SOUTHERLY INTO THIS EVENING BEFORE GOING CALM. ANY DEEP CONVECTION
THIS AFTN SHOULD REMAIN IN THE FOOTHILLS...WELL N AND W OF THE
FIELD. A BACK DOOR COLD FRONT WILL SAG SOUTHWARD OVERNIGHT AND THIS
WILL EVENTUALLY BACK WINDS TO NELY FOR FRI MRNG. THE EASTERLY FLOW
NORTH OF THE FRONT MAY ALLOW RESTRICTIVE STRATOCU TO FORM EARLY FRI
WHICH THE NAM AND ITS DERIVATIVES TRY TO BRING OVERHEAD AT OR JUST
AFTER DAYBREAK. THIS SEEMS QUESTIONABLE BUT NOT UNBELIEVABLE...SO
WILL CARRY A FEW MVFR LEVEL CLOUDS AT THAT TIME.

ELSEWHERE...ISOLD TO SCT SHRA/TSRA ARE EXPECTED TO FORM OVER
RIDGETOPS THIS AFTN BUT STAND ONLY A TINY CHANCE OF AFFECTING
KAVL...TOO LOW TO MENTION. OTHERWISE VFR THRU THIS EVENING WITH
SOMEWHAT VARIABLE WINDS...FAVORING NORTHERLY OVER THE NC SITES AND
SOUTHERLY SC. SOME MTN VALLEY FOG APPEARS LIKELY BUT WITH LOWER
CROSSOVER TEMPS ASSOCIATED WITH MIXING THIS AFTN...AND ASSUMING
SOILS STAY DRY...I LIMITED KAVL TO IFR/CAT-B. KHKY MAY SEE SOME LOW
STRATOCU ADVECT IN FRI MRNG AS NOTED FOR KCLT ABOVE. WINDS NELY OVER
THE NC PIEDMONT FRI WITH SELY ELSEWHERE.

OUTLOOK...THE AIRMASS WILL MOISTEN OVER THE WEEKEND TO SUPPORT ISOLD
TO SCT DIURNAL THUNDERSTORMS...ESPECIALLY ACROSS THE MTNS. MORNING
LOW CLOUDS AND FOG WILL REMAIN POSSIBLE DURING THE EARLY
MORNING...ESPECIALLY IN THE MTN VALLEYS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  98%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  94%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  89%     MED   79%
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...PM
NEAR TERM...WIMBERLEY
SHORT TERM...LG
LONG TERM...JAT
AVIATION...WIMBERLEY





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