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Area Forecast Discussion

596
FXUS62 KGSP 180846
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
446 AM EDT FRI APR 18 2014

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL DEVELOP IN THE NORTHEASTERN PART OF THE
GULF TODAY...AND TRACK EAST ACROSS NORTHERN FLORIDA TONIGHT. THIS
WILL SPREAD PRECIPITATION INTO THE REGION TONIGHT INTO SATURDAY.
COOL HIGH PRESSURE LINGERS BEHIND THE DEPARTING LOW SUNDAY AND
MONDAY. A COLD FRONT WILL CROSS THE AREA ON TUESDAY...FOLLOWED BY
DRY HIGH PRESSURE FOR THE REST OF THE WORKWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 440 AM EDT...CLOUD COVER HAS BEEN INCREASED SLIGHTLY ON THE
MOST RECENT UPDATE...AS MID AND HIGH LEVEL MOISTURE CONTINUE TO
THICKEN AND LOWER OVER THE REGION AHEAD OF THE SRN STREAM TROUGH
AXIS MOVING INTO THE LOWER MS RIVER VALLEY THIS MORNING. THE BEST
CONVECTION AND PRECIPITATION REMAIN LARGELY CONFINED TO THE FL
PANHANDLE AND SRN GA THIS MORNING...BUT WITH LIGHTER UPGLIDE RETURNS
STARTING TO SHOW UP ON REGIONAL RADARS OVER ERN GA IN IMPROVING
UPGLIDE. THE POP ONSET MAY NEED TO BE HASTENED IN SUBSEQUENT UPDATES
IF THIS LIGHT RAIN CAN OVERCOME THE SFC BASED DRY LAYER.

OTHERWISE...WEAK SFC HIGH PRES LINGERING ALONG THE NJ COAST WILL
KEEP A DRY CAD PATTERN OVER THE AREA EARLY TODAY AS THE CLOUDS
CONTINUE TO THICKEN AND LOWER. WILL LEAN COOLER THAN MOS ON MAX
TEMPS FOR TODAY. UPPER LEVEL DIVERGENCE WILL INCREASE RAPIDLY ACROSS
THE FORECAST AREA TODAY INTO TONIGHT AS A 500 MB LOW CENTER IN THE
UPSTREAM TROUGH CLOSES OFF OVER AL BY EVENING AND THEN MIGRATES
SLOWLY TOWARD THE SE COASTLINE OVERNIGHT. THE DEEPEST FORCING AND
MOISTURE AHEAD OF THIS SYSTEM WILL CROSS THE REGION TONIGHT.
ALTHOUGH THE GREATEST QPF SWATH MAY BE FOCUSED JUST SE OF THE
AREA....DEFORMATION ZONE PRECIPITATION AND UPSLOPE COULD STILL FOCUS
SOME HEAVIER PRECIPITATION NWD INTO OUR AREA. TWO QPF MAXIMA MAY
THUS SET UP...ONE IN THE LOWER PIEDMONT AND A SECONDARY AREA ALONG
THE SRN/SE ESCARPMENT AREAS...BUT WITH NEARLY ONE INCH RAINFALL
TOTALS IN BETWEEN AS FRONTOGENESIS DEVELOPS FROM THE LOWER PIEDMONT
TO THE BLUE RIDGE. PRECIPITABLE WATER VALUES ARE NOT ESPECIALLY
IMPRESSIVE AT A LITTLE OVER ONE INCH THROUGH TONIGHT...AND GIVEN THE
LACK OF A CLEAR TERRAIN FOCUS AND THE RELATIVELY SHORT DURATION OF
THE HEAVIER RAINFALL...A FLOOD WATCH IS NOT EXPECTED.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 300 AM FRIDAY...MODELS ARE IN GOOD AGREEMENT ON THE 500 MB LOW
SLOWLY WORKING ITS WAY EAST ROUGLY ALONG THE FL/GA BORDER ON
SATURDAY...KEEPING THE CWFA UNDER STRONG Q-VECTOR CONVERGENCE THRU
THE DAY. A SFC LOW WILL BE NEARLY RIGHT UNDER THE UPR LOW...WITH A
STIFF NE LLVL FLOW AND DEFORMATION ZONE PRECIP SHIELD LIKELY STILL
ACRS MUCH OF THE AREA AT LEAST THRU THE MORNING. I HAVE BUMPED UP
POPS THRU THE DAY...WITH A SLOWER DECREASING TREND IN THE AFTN. SFC
HIGH PRES BLDG INTO THE NORTHEAST STATES WILL SUPPLY COOL AIR...SO
TAKING A BLEND OF THE CONSRAW GUIDANCE...TEMPS WERE RATCHETED
DOWN...STAYING PRIMARILY IN THE 50S TO LWR 60S IN THE WEST.
ADDITIONAL QPF OF UP TO A QUARTER INCH IN THE SOUTHEAST ZONES IS
POSSIBLE.

BASED ON LATEST MODEL TRENDS...IT LOOKS LIKE THE WRAP-AROUND
MOISTURE AND LLVL NE FLOW LINGERS SATURDAY NIGHT AND EVEN INTO
SUNDAY. I HAVE POP TAPER OFF TO LESS THAN 15 PERCENT BY SUNDAY
MORNING...BUT CLOUDS SLOW TO CLEAR UNTIL ABOUT MIDDAY IN THE EAST.
GIVEN THE COOL NE FLOW...I DID BLEND IN CONSRAW TEMPS TO BUMP THEM
DOWN...ESP EAST OF THE MTNS.

A NARROW SFC RIDGE AXIS SETTLES OVER THE AREA SUNDAY NIGHT UNDER
RISING HEIGHTS ALOFT. TEMPS WILL BE NEAR NORMAL...SO NO FROST/FREEZE
CONCERNS ARE EXPECTED.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 215 AM FRIDAY...THE OP MODELS ARE IN GOOD AGREEMENT ON THE
PHASING OF REMNANT SRN STREAM ENERGY FROM A CLOSED UPR LOW INVOF
CALIF AND A NRN STREAM SHORTWAVE TROF DIGGING INTO THE GREAT LAKES
MONDAY INTO TUESDAY. THE RESULTANT PROPAGATING LATITUDINAL TROF WILL
PUSH A COLD FRONT THRU THE CWFA ON TUESDAY. THE GFS IS MOST BULLISH
ON INSTBY AND CONVECTIVE COVERAGE...WITH 600-800 J/KG OF SBCAPE.
OVERALL FORCING WITH THE FRONT LOOKS MODEST AT BEST...AND THE FCST
SNDGS SHOW A DEEP-LAYER UNIDIRECTIONAL WLY FLOW. SO NOT EXPECTING
MUCH MORE THAN SCATTERED SHWRS WITH PERHAPS A FEW TSTMS. THE BEST
COVERAGE WILL BE NEAR THE TN LINE...AS DOWNSLOPE MAY LIMIT COVERAGE
EAST OF THE MTNS.

AN UPR RIDGE BUILDS BACK IN BEHIND THE SHORTWAVE WEDNESDAY THRU
FRIDAY...WITH DRY WX ON TAP FOR THE REST OF THE WEEK.

TEMPS START OUT NEAR NORMAL MONDAY...THEN WARMING A COUPLE
CATEGORIES ABOVE NORMAL AHEAD OF THE FRONT TUESDAY...AND STAYING
ABOVE NORMAL WEDNESDAY THRU FRIDAY.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
AT KCLT...THE CLOUD BASE FORECAST REMAINS UNCERTAIN THIS
MORNING...WITH MODELS/MOS SPLIT ON GENERATING MVFR CIGS BY DAYBREAK
TODAY VERSUS KEEPING ANY CIGS AT MAINLY CIRRUS LEVELS. THE MORE
OPTIMISTIC SOLUTION IS BETTER MATCHING OBS THUS FAR...BUT WILL
CONTINUE TO HINT AT MVFR POSSIBLE WITH A SCT020 FORECAST AFTER 09Z.
THE HIGHER LEVEL VFR OVERCAST WILL STEADILY LOWER AND THICKEN
THROUGH THE DAY...WITH A RAPID TRANSITION TO MVFR THEN IFR CIGS
EXPECTED DURING THE LAST 6 HOURS OF THE TAF PERIOD AS RAIN DEVELOPS.
NE WINDS SHOULD BE LESS THAN 10 KT THROUGH THE FIRST HALF OF THE
PERIOD...BUT WITH INCREASING FLOW AND GUSTS LATE AS SFC LOW PRES
OVER SE GA TIGHTENS THE GRADIENT.

ELSEWHERE...MAINLY VFR MID AND HIGH CLOUDS ARE EXPECTED
EARLY...EXCEPT FOR A BETTER CHANCE OF MVFR THIS MORNING AT KAND IN
WEAK UPGLIDE OVER THE CAD LAYER. EXPECT MAINLY NE WINDS THROUGHOUT
TODAY...EXCEPT TOGGLING BETWEEN SE AND NRLY AT KAVL. CIGS SHOULD
DETERIORATE RAPIDLY LATE TODAY THROUGH TONIGHT FROM THE S AS BETTER
UPGLIDE MOISTURE AND UPPER SUPPORT ARRIVE. ANTICIPATE MVFR CIGS BY
EARLY EVENING...WITH IFR LIKELY AFTER 03Z ALONG WITH MODERATE TO
POSSIBLY HEAVY RAINFALL. IN ADDITION...A TIGHTENING PRES GRAD N OF
THE SE GA COASTAL LOW WILL PRODUCE NELY GUSTS ABOVE 20 KT AT THE
UPSTATE TAF SITES LATE IN THE PERIOD.

OUTLOOK...CEILING AND VISIBILITY RESTRICTIONS WILL LINGER WELL INTO
SAT AS A SE COASTAL LOW PRESSURE SYSTEM PULLS SLOWLY AWAY. DRY HIGH
PRES WILL RETURN SUNDAY INTO MONDAY...WITH A FAIRLY WET FRONTAL
SYSTEM EXPECTED ON TUE.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-08Z
KCLT       MED   73%     HIGH 100%     HIGH  88%     MED   70%
KGSP       HIGH  80%     HIGH 100%     MED   63%     MED   72%
KAVL       HIGH 100%     HIGH 100%     HIGH  88%     HIGH  98%
KHKY       HIGH  81%     HIGH 100%     HIGH 100%     MED   68%
KGMU       HIGH  80%     HIGH 100%     MED   63%     MED   79%
KAND       MED   71%     MED   64%     MED   68%     MED   75%

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...ARK
NEAR TERM...HG
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...HG






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