Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 251952
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
252 PM EST WED FEB 25 2015

.SYNOPSIS...
A MOIST AREA OF LOW PRESSURE WILL MOVE UP THE CAROLINA COAST
THROUGH THE OVERNIGHT. THIS SYSTEM WILL BRING A QUICK SHOT OF
SIGNIFICANT WINTRY WEATHER TO THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA INTO THURSDAY. 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 THURSDAY/...
AT 230 PM...THE 12Z OPERATIONAL MODELS AS WELL AS STATISTICAL
GUIDANCE STILL SOLIDLY SUPPORTS A SIGNIFICANT WINTER EVENT OVER
THE WESTERN CAROLINAS AND NE GA TONIGHT. HENCE...WILL CONTINUE
THE WINTER STORM WARNING FOR THE ENTIRE FORECAST AREA. THE
VIGOROUS SOUTHERN STREAM WAVE WILL CROSS THE AREA OVERNIGHT WITH
ITS ATTENDANT SURFACE LOW MOVING OFF THE SC COAST BY 12Z THU.
PRECIP WILL RAPIDLY OVERSPREAD THE REGION FROM LATE THIS AFTERNOON
INTO THE EARLY EVENING HOURS. ALL SORTS OF DYNAMICAL FORCING WILL
OCCUR OVER THE WESTERN CAROLINAS AND NE GA TONIGHT. NO NEED TO GO
INTO DETAILS ON THAT. THE BIGGEST ISSUE CONTINUES TO BE WHERE THE
MOST SIGNIFICANT BANDING WILL DEVELOP AND ALSO WHERE THE RAIN/SNOW
LINE WILL SET UP. STILL EXPECT THAT DYNAMICAL COOLING WILL BECOME
SUFFICENT TO COOL THE BOUNDARY LAYER ENOUGH EAST OF THE MOUNTAINS
FOR SNOW PROFILES TO PREDOMINATE A COUPLE HOURS AFTER THE ONSET OF
PRECIP MOST AREAS. HOWEVER...THE PRECIP IS STILL EXPECTED TO BEGIN
AS RAIN MOST AREAS OUTSIDE THE MOUNTAINS. THE MAIN ADJUSTMENT WITH
THE SNOWFALL TOTALS IS NOW TO SHOW THE MAXIMUM FROM THE EASTERN
UPSTATE...NORTHEAST THROUGH THE CHARLOTTE METRO AREA WHERE 8-10
INCHES IS EXPECTED. LATEST GUIDANCE SHOWS A LITTLE FARTHER
NORTHWARD TRACK OF THE SFC LOW WHICH BRINGS A SWATH OF HIGHER QPF
INTO THAT AREA OVERNIGHT. ALSO...MESO MODELS ARE HITTING THAT AREA
WITH THE HIGHEST QPF. IT ALSO SHOULD BE MENTIONED THAT SOME
CONVECTIVE ELEMENTS COULD PRODUCE LOCALLY HIGH SNOWFALL TOTALS IN
SOME AREAS. THE FFC MORNING SOUNDING SHOWED CONSIDERABLE WARM NOSE
BELOW 700 MB SO THE RAIN/SNOW LINE IS LIKELY TO SET UP FROM
SOMEWHERE OVER NORTH GA...EASTWARD THROUGH ELBERT COUNTY
GA...ABBEVILLE AND GREENWOOD COUNTIES SC. THUS...SNOWFALL ACROSS
THE SOUTHERN UPSTATE COULD BE QUITE VARIABLE FROM THE NORTH TO
SOUTH. OF COURSE THE BIGGEST WILD CARD WILL BE THE POSITION OF THE
SNOW/RAIN LINE ACROSS THE LOWER PIEDMONT COUNTIES.

THE SNOW WILL END RAPIDLY FROM WEST TO EAST AFTER MIDNIGHT AND
SHOULD BE EAST OF THE AREA BY 12Z THU. THU SHOLD BE DRY OTHER THAN
FOR SOME SCT SW- OVER THE ESCARPMENT DUE TO UPSLOPE FLOW. USED
PRIMARLILY A BLEND OF NAM/GFS FOR MOST FIELDS TONIGHT TRYING TO
CAPTURE THE EXTENT OF DYNAMIC COOLING. ALSO SHADED MAX TEMPS ON THU
TOWEARD THE COOLEST RAW GFS NUMBERS IN DEFERENCE TO SNOW...AND THAT
MAY NOT BE LOW ENOUGH.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 130 PM WEDNESDAY...FRIDAY...THE SFC PATTERN WILL FEATURE THE
APPROACH OF THE NORTHERN PLAINS 1040 MB HIGH PRESSURE AND LOW
PRESSURE OFF THE MID ATLANTIC COAST. THIS PATTERN WILL SUPPORT
MODEST CAA ACROSS THE MTNS WITH H85 WINDS AROUND 15KTS. WEAK FLOW
MAY SUPPORT ISO TO SCT SHSN ACROSS THE TN BORDER COUNTIES...WITH
LITTLE TO NO ACCUMULATION. TEMPERATURES ARE FORECAST TO REMAIN WELL
BELOW NORMAL...RANGING FROM 15 TO 20 DEGREES BELOW NORMAL. LOWS IN
THE 20S AND HIGHS REMAINING IN THE 20S TO 30S ACROSS THE MTNS TO LOW
40S EAST.

ON SATURDAY...THE CENTER OF THE CANADIAN AIR MASS WILL BUILD ACROSS
THE SOUTHERN APPALACHIAN REGION. H85 TEMPS MAY COOL TO -10C ACROSS
PORTIONS OF THE I-40 CORRIDOR. A BLEND OF MOS GUIDANCE SUPPORTS
TEMPERATURES FALLING TO THE LOW 20S ACROSS THE NC ZONES...WITH MID
TO UPPER 20S SOUTH. COLD THICKNESSES AND MOSTLY TO PARTLY CLOUDY SKY
COVER WILL LIMIT HIGHS TO THE 30S ACROSS THE MTNS AND NC FOOTHILLS
TO LOW 40S ACROSS THE UPPER SAVANNAH RIVER VALLEY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 130 PM WEDNESDAY...THE MEDIUM RANGE LOOKS QUITE UNSETTLED PER
THE MODEL CONSENSUS. THE OVERALL UPPER PATTERN WILL SHIFT TO A
GRADUALLY DEEPENING WESTERN CONUS TROF AND BUILDING EASTERN RIDGE.
THIS WILL PUT THE SOUTHEAST STATES WITHIN BROAD DEEP LAYER
SOUTHWESTERLY FLOW. AT THE SFC...COOL HIGH PRES WILL SLOWLY SHIFT
EAST OFF THE EAST COAST...ALLOWING A SLOW-MOVING ANAFRONT TO SAG
SOUTHEAST INTO THE REGION...LIKELY SUNDAY NIGHT OR MONDAY. POPS WERE
CUT BACK FOR SATURDAY NIGHT. AND SUNDAY/S POPS MAY STILL BE
OVERDONE...AS MODELS TREND LATER WITH THE FRONT/S ARRIVAL. ONCE THE
FRONT PUSHES THRU THE AREA AND STALLS EAST-WEST ALONG THE GULF
STATES...ROUNDS OF PRECIP ARE INDICATED IN THE MODELS ASSOCIATED
WITH SHORTWAVES EJECTING OUT OF THE WESTERN TROF. FROM SUNDAY NIGHT
THRU WEDNESDAY...USING THE SUPERBLEND GUIDANCE...POPS ARE HIGH-END
CHC TO LIKELY EVERY PERIOD STARTING SUNDAY NIGHT. GRANTED...THERE
WILL LIKELY BE LULLS IN PRECIP DURING THIS PERIOD...BUT CONFIDENCE
IN TIMING THIS FAR OUT IS TOO LOW TO GET INTO THE GRIDS. AS FOR
TEMPS...WITH THE BUILDING UPPER RIDGE...THICKNESSES LOOK TO WARM TO
LIMIT WINTER PRECIP TYPE CONCERNS. IF SOME PRECIP IS ABLE TO DEVELOP
AHEAD OF THE ANAFRONT WITHIN THE LINGERING DRIER HIGH PRES...THERE
MAY BE SOME WINTRY MIX...MAINLY IN THE MTNS OR NC FOOTHILLS.
OTHERWISE...I HAVE PRECIP ADVERTISED AS RAIN THRU THE PERIOD. TEMPS
WILL START OUT BELOW NORMAL OVER THE WEEKEND...WARMING TO NEAR
NORMAL FOR MON-TUE...THEN ABOVE NORMAL FOR WEDNESDAY.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...A DYNAMIC WINTER STORM WILL QUICKLY SPREAD
PRECIP OVER THE AREA BY 00Z. BOUNDARY LAYER TEMPS ARE WARM ENOUGH TO
ALLOW PRECIP TO BEGIN EITHER AS RAIN OR RA/SN MIX. STILL EXPECTING
ENOUGH COOLING ALOFT TO ALLOW FOR ALL SNOW IN THE 00Z-02Z TIMEFRAME.
EXPECT CIGS/VSBYS TO LOWER TO LIFR IN MOD/HEAVY SNOW IN THE 01Z-07Z
TIMEFRAME. SNOW MOVES OUT QUICKLY AFTER 07Z ALLOWING VSBYS TO
INCREASE RAPIDLY...BUT REMANT LOW LEVEL MOISTURE SUPPORTS ONLY
SLOWLY IMPROVING CIG CONDITIONS TO IFR BY 12Z AND THEN MVFR BY 18.

OUTLOOK...LOW LEVEL MOISTURE WILL LINGER THROUGH THE REMAINDER OF
THE WEEK...WITH VARIABLE AMOUNTS OF CIG HGT RESTRICTIONS THRU FRIDAY.

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 STORM WARNING UNTIL 7 AM EST THURSDAY FOR GAZ010-017-
     018-026-028-029.
NC...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NCZ033-
     035>037-048>053-056>059-062>065-068>072-082-501>510.
SC...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR SCZ001>014-
     019.

&&

$$
SYNOPSIS...SBK
NEAR TERM...LG
SHORT TERM...NED
LONG TERM...ARK
AVIATION...LG



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