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Area Forecast Discussion

971
FXUS62 KGSP 032356
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
656 PM EST TUE MAR 3 2015

.SYNOPSIS...
MOIST AND MILDER AIR WILL RETURN TO THE AREA WEDNESDAY AHEAD OF AN
APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS THROUGH THE
AREA ON THURSDAY...WITH COOL AND DRY HIGH PRESSURE RETURNING FOR
FRIDAY AND INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 630 PM...WEDGE BNDRY BEGINNING TO BREAK DOWN CURRENTLY WITH
WINDS SHIFTING AND BECOMING WEAK. WINDS WILL PICK UP AND BECOME S/LY
OVER THE NEXT SEVERAL HRS AND PUSH A WEDGE WARM FRONT NORTH. THIS
WILL KEEP CLOUDS LOW AND BEGIN LOWERING VSBYS WITH WARM SFC THETA/E
ADV. NO SIGFNT CHANGES WERE MADE TO THE FCST GRIDS.

AS OF 430 PM...NO MAJOR CHANGES WERE NEEDED TO THE GOING FCST. ISEN
CHARTS AT 285K INDICATE CPD/S WILL REMAIN VERY LOW WHILE THE WEDGE
CONTINUES TO BREAK DOWN...SO LOW CLOUDS AND AREAS OF VERY LIGHT RAIN
AND PATCHY DZ WILL CONTINUE THROUGH THE NEXT UPDATE. ALIGNED POPS
CLOSE TO CAM POPS WITH THE BETTER COVERAGE REMAINING OVER THE SW/RN
ZONES IN MECH LIFT.

AS OF 1230 PM...PATCHES OF LIGHT RAIN AND DRIZZLE CONTINUE TO MOVE
EAST MAINLY ACROSS NE GEORGIA AND UPSTATE SC...AND THE SRN PART OF
THE CLT METRO AREA. THIS WAS IN GENERAL AGREEMENT WITH SOME OF THE
MESOSCALE MODELS. THE LIGHT PRECIP AND CLOUD COVER HAS KEPT TEMPS
COOL AND IN LINE WITH PREVIOUS THINKING. NO SIGNIFICANT CHANGES WILL
BE MADE.

FOR TONIGHT...A SLOWLY EVOLVING UPPER PATTERN WITH THE AXIS OF AN
UPPER RIDGE MOVING OFF THE E COAST WILL CARRY SURFACE HIGH PRESSURE
AWAY AND FURTHER OFFSHORE...THUS REMOVING ANY CONNECTION BETWEEN THE
PARENT HIGH AND OUR WEAK HYBRID WEDGE. AT THE SAME TIME...MOIST
ISENTROPIC LOW LEVEL UPGLIDE WILL SHIFT TO THE NE...CARRYING MOST OF
THE LEFTOVER LIGHT RAIN WITH IT. THAT WILL LEAVE MOST OF THE
PIEDMONT MAINLY DRY OVERNIGHT WITH WINDS COMING AROUND TO THE SE OR
S TO MOVE OUT THE REMNANTS OF THE LOW LEVEL COOL POOL. AS THIS
HAPPENS...CANNOT RULE OUT A PERIOD OF PATCHY DENSE FOG AS WARM
ADVECTION BEGINS NEAR THE SURFACE. THE WARM ADVECTION SHOULD RESULT
IN TEMPERATURES RISING GRADUALLY OVERNIGHT. A CHANCE OF PRECIP WILL
BE RETAINED OVER THE MTNS AND FOOTHILLS WHERE SOME SMALL UPSLOPE
COMPONENT WILL CONTINUE. FORTUNATELY...TEMPS WILL REMAIN ABOVE
FREEZING SO NO P-TYPE PROBLEMS ARE EXPECTED.

ON WEDNESDAY...THE MODELS SHOW A CLASSIC ANAFRONT APPROACHING SLOWLY
FROM THE WEST AS IT FIGHTS ITS WAY AGAINST THE WSW FLOW ALOFT.
FORCING E OF THE MTNS WILL BE MINIMAL...OTHER THAN THE LOW LEVEL
WARM ADVECTION...WHICH SUPPORTS KEEPING A POP GRADIENT UP AGAINST
THE HIGHER TERRAIN. THE PRECIP PROBABILITY RAMPS BACK UP TO LIKELY
IN THE MORNING AND THEN CATEGORICAL IN THE LATE AFTERNOON ALONG THE
TN BORDER AS THE FRONT MOVES IN. SOME LOW MU CAPE SUGGESTS THERE
COULD BE SOME EMBEDDED THUNDERSTORMS ALONG THE FRONT. TEMPS AHEAD OF
THE FRONT WILL BOUNCE BACK 20 TO 25 DEGREES ABOVE TUESDAYS HIGHS...
CONTINUING OUR RECENT ROLLER COASTER STRETCH OF HIGH TEMPS.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AT 230 PM EST TUESDAY...THE SHORT TERM PERIOD INITIALIZES ON
WEDNESDAY EVENING AMIDST FLAT UPPER RIDGING ALOFT OVER THE
SOUTHEAST WHILE A SHORT WAVE TROF DIGS ACROSS THE NORTHERN PLAINS.
AT THE SURFACE...WAA REGIME PREVAILS ACROSS THE SOUTHEAST AHEAD OF
AN APPROACHING COLD FRONT.  THE FCST INITIALIZES WITH LIKELY POPS
ACROSS THE HIGH TERRAIN AS THE PRIMARY MOISTURE/FRONTAL AXIS SLIDES
THROUGH THE TENNESSEE VALLEY...WITH SOME UPSLOPE ENHANCEMENT
POSSIBLE.  POPS DECREASE FURTHER EAST WITH NO MENTIONABLE POPS AT
INITIALIZATION ALONG AND SOUTH OF INTERSTATE 85.  POPS WILL
GRADUALLY RAMP UP THROUGH THE OVERNIGHT INTO THE THURSDAY MORNING AS
THE FRONT INTRUDES FROM THE WEST...WITH WIDESPREAD LIKELY LEVEL
POPS FEATURED BY MIDDAY.

MODELS CONTINUE TO HINT AT WEAK INSTABILITY AHEAD OF THE FROPA IN
THE WARM SECTOR...WHICH COULD PROMOTE A FEW RUMBLES OF THUNDER
ACROSS PORTIONS OF NORTHEAST GA...AND THE WESTERN CAROLINAS EARLY ON
THURSDAY.  OTHERWISE...AS COLD ADVECTION PREVAILS BEHIND THE
FRONT...EXPECTING A FAIRLY QUICK TRANSITION OF PTYPE ALONG THE TN
LINE BEFORE ALL PRECIP EXITS THE REGION INTO THE LATE AFTERNOON
HOURS.  EXPECTING PHASES CHANGES FROM RAIN TO A BRIEF PERIOD OF
FREEZING RAIN BEFORE SLEET THEN FINALLY SNOW...ALL WITHIN 6-8
HOURS.  NOT EXPECTING ANY ACCUMULATIONS TO EXCEED ADVISORY LEVELS.

BEYOND THAT...THE FRONT WILL SLIDE EAST THROUGH THURSDAY EVENING
WITH ALL POPS REMOVED FROM THE FCST NLT MIDNIGHT.  HIGH PRESSURE
WILL QUICKLY SLIDE IN BEHIND THE FRONT ACROSS THE OHIO VALLEY BEFORE
SETTING UP A BRIEF CAD WEDGE REGIME FOR EARLY FRIDAY.
THUS...EXPECTING FRIDAY TO BE DRY...WITH CLOUDY SKIES EARLY ON
BEFORE WEAK WEDGE QUICKLY RETREATS AND SUNNY SKIES PREVAIL BY THE
AFTERNOON HOURS.  TEMPERATURES THROUGH THE PERIOD WILL FEATURE NEAR
NORMAL LEVELS ON THURSDAY BEFORE FALLING TO WELL BELOW NORMAL FOR
FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 200 PM TUE...HIGH PRESSURE WILL REMAIN IN CONTROL OVER THE
CAROLINAS AND VICINITY FRI NIGHT THRU MON. A SHALLOW ERN CONUS TROUGH
WILL STILL BE PRESENT ALOFT...AND THE THE NORTHERN STREAM WILL REMAIN
SOMEWHAT ACTIVE. A WEAK COLD FRONT WILL SWEEP THRU SAT NIGHT OR SUN
BUT WITH VERY LITTLE MOISTURE...ALBEIT ENOUGH TO MENTION SOME UPSLOPE
POPS ALONG THE TENN BORDER. THE FRONT WILL BASICALLY ALLOW A
TRANSITION FROM ONE SFC HIGH TO ANOTHER...THOUGH LITTLE TO NO CHANGE
IN TEMPS IS EXPECTED. THICKNESSES INCREASE GRADUALLY OVER THE COURSE
OF THE PERIOD AND MIN/MAX TEMPS WILL BE NEAR CLIMO BY SUNDAY. THE
SECOND AREA OF HIGH PRESSURE WILL MOVE OFFSHORE EARLY-MID NEXT WEEK
AS SPLIT FLOW DEVELOPS IN THE SRN STREAM...LEADING TO THE DEVELOPMENT
OF A WAVE ALONG THE STALLED BOUNDARY OVER THE NRN GULF OF MEXICO.
GLOBAL MODELS DIFFER ON THE TIMING OF THIS FEATURE...BUT EVENTUALLY
SAID WAVE COULD SPREAD WARM FRONTAL PRECIP INTO THE CWFA. 03/00Z AND
12Z EC BOTH DO SO BY MONDAY NIGHT...BUT THE 03/12Z GFS DELAYS IT
UNTIL WELL BEYOND THE END OF THE FCST PERIOD. LOW POPS WILL RETURN
ACROSS THE CWFA IN A NOD TO THE EC SOLUTION. SFC TEMPS WILL DIP BELOW
FREEZING OVER MUCH OF THE HIGHER TERRAIN MON NIGHT. IN LIGHT OF THE
STRONG WARM NOSE THAT WOULD BE EXPECTED...SOME LIGHT FZRA MAY OCCUR
THERE.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...A COMPLICATED TAF SET AND WILL SIDE ON THE PESSIMISTIC
END. THE CURRENT WEDGE CONFIG IS BEGINNING TO BREAK DOWN AND THIS
WILL ALLOW THE WEDGE WARM FRONT TO PUSH NORTH THROUGH THE OVERNIGHT.
CIGS SHOULD DROP INTO LIFR AND LIFR VSBY BY 11Z IN AN ADVECTIVE FG
BASED ON HIGHER SFC THETA/E PUSHING NORTH. WIND SHEAR WILL BE
UNIDIRECTIONAL BUT STRONG BTW 07Z-11Z OR SO. A GRADUAL IMPROVEMENT
AFT 15Z TO MVFR WITH DECENT WIND GUSTS IN THE AFTERNOON.

ELSEWHERE...NON/MTN TAF SITES SIMILAR TO KCLT. VSBY AT KAVL AND KHKY
MAY NOT BE AS DENSE DUE TO THE SLOWER ADVANCE OF HIGHER SFC
THETA/E...HOWEVER PRECIP FALLING ACROSS THOSE TERMINALS CURRENTLY
COULD TRUMP THE ADV FG SCENARIO IF WINDS WEAKEN ENUF. RIGHT NOW WILL
COUNT ON ENUF LLVL MIXING TO MINIMIZE THE DENSE FG THREAT. WIND SHEAR
WILL BE MORE PREVALENT AND LONGER IN THE HIGHER ELEVS...BUT ALL
SITES WILL EXPERIENCE PRETTY STRONG SHEAR AT 2 KFT AFTER 08Z. DENSE
FG SHOULD PERSIST ACROSS THE SC SITES THROUGH MID MORNING...WITH A
GENERAL IMPROVEMENT SOME GUSTS THROUGH THE AFTERNOON.

OUTLOOK...A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION WEDNESDAY
NIGHT THROUGH THURSDAY...BRINGING CHANCES FOR HEAVIER RAINFALL AND
LOW CIGS/VSBYS TO THE AREA. VFR CONDITIONS ARE EXPECTED TO RETURN
FOR FRIDAY AND SATURDAY.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     HIGH 100%     HIGH 100%     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...WIMBERLEY
NEAR TERM...PM/SBK
SHORT TERM...CDG
LONG TERM...WIMBERLEY
AVIATION...SBK



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