Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261131
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
631 AM EST THU FEB 26 2015

.SYNOPSIS...
LOW PRESSURE WILL MOVE AWAY FROM THE CAROLINA COAST TODAY AS A COLD
FRONT SLOWLY CROSSES FROM THE WEST.  COLD CANADIAN HIGH PRESSURE
WILL BUILD IN FRIDAY AND SLOWLY WARM THROUGH THE WEEKEND...WITH
ABOVE NORMAL TEMPERATURES RETURNING TO THE AREA BY MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM EST THURSDAY...SLASHED POPS ACROSS THE VAST MAJORITY OF
THE AREA THROUGH MID MORNING WITH SLIGHT/CHANCE POPS CONTINUING
THROUGH THE REMAINDER OF THE PERIOD ALONG THE TN LINE AS WEAK NWFS
REGIME ESTABLISHES.  OTHERWISE...STILL FORECASTING TEMPS TO WARM
INTO THE UPPER 30S TO LOWER 40S ACROSS LOWER TERRAIN OF GA/SC/NC
TODAY WHICH AIDED BY OCCASIONAL BREAKS IN SKY COVER...WILL WORK TO
MELT SOME OF THE SNOW COVER.  AS FOR PRODUCTS...WINTER STORM WARNING
HAS BEEN CANCELLED ENTIRELY AND REPLACED WITH A WINTER WEATHER
ADVISORY SPECIFICALLY HIGHLIGHTING SLICK ROADWAY CONDITIONS THROUGH
MIDDAY.

PREVIOUS DISCUSSION...

AS OF 330 AM EST THURSDAY...SATURATED BOUNDARY LAYER CONTINUES TO
YIELD VERY LOW CEILINGS AND REDUCED VISB THIS MORNING AMIDST LIGHT
NORTHEAST WINDS. MODERATE TO HEAVY RA/SN IS COMING TO AN END ACROSS
THE REGION AS DRY SLOT WORKS IN BEHIND DEPARTING SURFACE WAVE.
THEREFORE WILL CANCEL WARNING FOR THE VAST MAJORITY OF THE SC
UPSTATE...ALL OF NORTHEAST GA...AND THE SOUTHWEST MTNS OF WESTERN
NC.  THIS WILL BE REPLACED WITH A WINTER WEATHER ADVISORY TO
HIGHLIGHT CONTINUED HAZARDOUS DRIVING CONDITIONS THROUGH 12Z.  WILL
CONTINUE WITH THE CURRENT WARNING OVER NC PIEDMONT AND NORTHERN MTNS
AS SOME LIGHT RETURNS REMAIN ON RADAR.  AS FOR THE FCST...POPS WILL
INITIALIZE AT LOW END CHANCE LEVELS ACROSS NORTHEAST GA....SOUTHWEST
NC...AND THE WESTERN UPSTATE OF SC...WITH AN INCREASING GRADIENT TO
THE NORTHEAST WHERE LIKELY POPS RESIDE ALONG THE I77 CORRIDOR.  FROM
THERE...WILL TREND POPS DOWN THROUGH THE REMAINDER OF THE MORNING
OVER THE ENTIRE FCST AREA WITH POPS LINGERING AT CHANGE TO SLIGHT
CHANCE LEVELS THROUGH THE AFTERNOON ACROSS THE MTNS OF WESTERN NC.

MODELS INDICATE A LULL IN PRECIP ALONG THE HIGHER TERRAIN BEFORE
WEAK NORTHWEST FLOW REGIME ESTABLISHES ITSELF ALONG THE WINDWARD
SIDE OF THE SOUTHERN/CENTRAL APPS LEADING TO SLIGHTLY HIGHER CHANCE
POPS INTO LATE EVENING.  PROFILES AT THE TIME WILL SUPPORT SNOW
SHOWERS WITH MODEL QPF BEING LOW ENOUGH TO INHIBIT ANY SIGNIFICANT
ADDITIONAL ACCUMULATIONS.  OTHERWISE...EXPECTING TEMPERATURES TO
WARM INTO THE UPPER 30S/40S ACROSS THE REGION THIS AFTERNOON DESPITE
OVERCAST SKIES.  THIS WILL AID MELTING PROCESSES OF SNOWPACK ON THE
GROUND ALREADY.  AS TEMPERATURES FALL TO SUBFREEZING LEVELS
REGIONWIDE INTO THURSDAY NIGHT...EXPECTING HAZARDOUS DRIVING
CONDITIONS TO REEMERGE ON ANY WET/REFREEZING HIGHWAYS.  ISSUANCE OF
ANOTHER WINTER WEATHER ADVISORY MAY BE WARRANTED LATER IN THE DAY TO
COVER SUCH.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 230 AM THURSDAY...SOME INTERESTING LITTLE PROBLEMS IN THE FCST
FOR THE END OF THE WEEK...MAINLY BECAUSE OF MODEL DIFFERENCES WITH
HANDLING BOUNDARY LAYER MOISTURE. OVERALL...THE WESTERN CAROLINAS
WILL BE UNDER A NEARLY ZONAL FLOW ALOFT...WITH SOME WEAK RIDGING IN
THE NRN STREAM SUPPORTING A COLD HIGH MOVING PAST TO THE NORTH
THROUGH SATURDAY. NW FLOW SNOW SHOWERS SHOULD CONTINUE TO GRADUALLY
TAPER OFF ON THE TN BORDER FRIDAY MORNING. AFTER THAT...THE FIRST
MINOR PROBLEM IS THE MOISTURE TRAPPED UNDERNEATH THE SUBSIDENCE
INVERSION ON THE GFS ON FRIDAY. THE GFS USES THAT MOISTURE TO
DEVELOP SHALLOW CONVECTION OVER THE PIEDMONT AND FOOTHILLS OF THE
CAROLINAS IN THE AFTERNOON AND EVENING...THAT WOULD RESULT IN
SCATTERED RAIN/SNOW SHOWERS. MEANWHILE...THE OPERATIONAL NAM DOES
NOT...BECAUSE OF MUCH LESS MOISTURE IN THE BOUNDARY LAYER. PREFER TO
KEEP THE FCST DRY FRIDAY AFTERNOON AND EVENING UNTIL THERE IS BETTER
AGREEMENT. THE HIGH SHOULD MOVE INTO POSITION ON SATURDAY TO OUR NE
TO SUPPORT COLD AIR DAMMING. EXPECT TEMPS TO REMAIN WELL BELOW
NORMAL ON SATURDAY AS A RESULT. THE NEXT PROBLEM ARISES SATURDAY
NIGHT WITH THE HIGH SLIPPING OFF THE MID ATLANTIC COAST. THE ISSUE
WILL BE HOW QUICKLY MOISTURE RETURNS FROM THE GULF/ATLANTIC AND
MOVES ISENTROPICALLY UP AND OVER THE SHALLOW COOL BOUNDARY LAYER.
THE MODELS GENERALLY AGREE THAT THE BETTER MOISTURE RETURN WILL
FOCUS ON GEORGIA AND ALABAMA THRU 12Z SUNDAY. THE NAM DEVELOPS LIGHT
PRECIP ACROSS MOST OF THE FCST AREA W OF I-77 INTO SUB-FREEZING AIR
AT THE SFC...TO THE POINT WHERE A FREEZING RAIN ADVISORY WOULD BE
NEEDED ACROSS MOST OF THE REGION. MEANWHILE...THE ECMWF AND GFS
REMAIN DRY ACROSS THE REGION THROUGH 12Z SUNDAY. AT THIS POINT...
PREFER TO SIDESTEP THE ISSUE AND FAVOR THE DRY SOLUTIONS...WHICH
HAVE SUPPORT FROM THE MEAN QPF ON THE 03Z SREF. WILL RAMP UP THE
PRECIP CHANCES IN A DEVELOPING COLD AIR DAMMING WEDGE SUNDAY MORNING
AS TEMPS RISE SLOWLY THROUGH THE 30S. MAX TEMPS WILL REMAIN WELL
BELOW NORMAL...PROBABLY BARELY REACHING THE LOWER 40S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 330 AM THURSDAY...THE MEDIUM RANGE STILL PROMISES AN UPPER
PATTERN CHANGE WITH RIDGING IN THE EAST...EVEN THOUGH IT LOOKS KIND
OF BROAD AND FLAT. THE MAIN ISSUE WILL BE A SURFACE BOUNDARY THAT
THE MODELS DROP DOWN FROM THE NW ON SUNDAY NIGHT AND THEN LAY OUT
ACROSS THE REGION E TO W ON MONDAY AND INTO TUESDAY. THIS WILL
NECESSITATE A CHANCE POP THROUGH MUCH OF THE PERIOD...WHICH WILL AT
LEAST BE FOR RAIN...AS TEMPS SHOULD STAY ABOVE FREEZING. HAVE NOT
MADE MANY CHANGES TO THE FCST THROUGH THE PERIOD. THE HIGH TEMP ON
TUESDAY LOOKS PARTICULARLY CHALLENGING AS THERE ARE INDICATIONS OF
ANOTHER TRANSITORY HIGH TO THE NORTH PROVIDING FOR ANOTHER WEDGE.
THE HIGH MOVES AWAY TUESDAY NIGHT...AND THE MEAN SW FLOW SHOULD
DESTROY ANY REMAINING WEDGE-LIKE FEATURE ON WEDNESDAY.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...VFR/MVFR CONDITIONS WILL PREVAIL AT TIMES AT
ALL SITES.  INITIALIZED ALL TAFS EITHER VFR...OR WITH A SHORT PERIOD
OF MVFR SPECIFICALLY ACROSS WESTERN NC WHERE LINGERING LOW CIGS
DOMINATE FROM ERODING SN SHOWERS.  OTHERWISE...GUIDANCE HAS TRENDED
TOWARDS IMPROVEMENT OF CIGS THROUGH MORNING WITH POSSIBLY ANOTHER
ROUND OF HIGH END MVFR AROUND EARLY EVENING AS ANOTHER MID/UPPER
WAVE SLIDES ATOP MOIST LAYER.  WINDS THROUGH THE PERIOD WILL REMAIN
LIGHT AND NORTHEASTERLY AHEAD OF A TRANSITIONING HIGH WHEN FLOW WILL
BE VRB/NW IN THE 3-4KTS RANGE.

OUTLOOK...LOW LEVEL MOISTURE WILL LINGER THROUGH THE REMAINDER OF
THE WEEK AND INTO THE WEEKEND AS WEDGE BUILDS FROM THE NORTH.
FLIGHT RESTRICTIONS WILL BE POSSIBLE THROUGH THIS
TIMEFRAME...ESPECIALLY ON SUNDAY WHEN MOISTURE SPREADS IN FROM THE
SOUTH.

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...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR GAZ010.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
     GAZ017-018-026-028.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-
     035>037-048>053-056>059-062>065-072-501>510.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
     NCZ068>071-082.
SC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR SCZ001>003.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
     SCZ004>010.

&&

$$
SYNOPSIS...DEO
NEAR TERM...CDG
SHORT TERM...PM
LONG TERM...PM
AVIATION...CDG


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