Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 250845
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
345 AM EST WED FEB 25 2015

.SYNOPSIS...
LOW PRESSURE WILL ORGANIZE OVER THE NORTHERN GULF AND MOVE TO THE
CAROLINA COAST LATE TONIGHT. THIS SYSTEM WILL BRING A QUICK SHOT OF
SIGNIFICANT WINTRY WEATHER TO THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA. EXPECT COLD CANADIAN HIGH PRESSURE TO BUILD SOUTHEAST FROM
THE DAKOTAS ON THURSDAY...THEN BECOME CENTERED OVER THE OHIO VALLEY
FRIDAY NIGHT.  EXPECT BELOW NORMAL TEMPERATURES THROUGH THE
WEEKEND...THEN WARMER WEATHER NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM EST WEDNESDAY...SIGNIFICANT WINTER STORM STILL ON TRACK
TO OVERTAKE THE REGION WEDNESDAY AFTERNOON/NIGHT.  DEVELOPING
SURFACE CYCLONE AIDED BY EASTWARD ADVECTING POTENT UPPER SHORT WAVE
IS GAINING STEAM ACROSS SOUTH TEXAS INTO THE WESTERN GULF THIS
MORNING.  THIS SURFACE WAVE IS STILL PROGGED TO SLIDE ALONG THE GULF
COAST CROSSING NORTH FL...SOUTHERN GA/SC THIS EVENING.  MODELS STILL
TRANSLATE AMPLE QPF RESPONSE ATOP THE REGION BY WAY OF ENHANCED
UPGLIDE AIDED BY COUPLED JET ALOFT PROVIDING NICE UPPER SUPPORT.
LIKEWISE...LATEST NAM12 ANALYSIS INDICATES AMPLE H7 FRONTOGENESIS
ALONG THE NORTHERN FLANK OF THE SYSTEM AS IT SLIDES BY TO THE SOUTH
AROUND THE 21Z-03Z TIMEFRAME.  GIVEN ALL THE ABOVE...WOULD NOT BE
SURPRISED TO SEE IMPRESSIVE MESOSCALE BANDING OF SNOWFALL WITH THIS
SYSTEM.  HIGH PRESSURE TO THE NORTH WILL BE ON THE MOVE WITH MODEST
SURFACE COLD ADVECTION ASSOCIATED WITH IT.  THE PRIMARY FCST
CHALLENGE WITH THIS SYSTEM IS WHERE/WHEN WILL THE RASN/SN LINE SETUP
THIS EVENING...AND HOW DOES THAT LINE UP WITH FCST QPF.

FCST FEATURES INCREASING POPS FROM THE SOUTHWEST JUST BEFORE NOON
WITH THERMAL PROFILES SUPPORTING ALL RAIN.  FURTHER INTO THE
AFTERNOON POPS SPREAD NORTH OVER THE SOUTHWEST NC MOUNTAINS...ALL OF
NORTHEAST GA AND THE WESTERN HALF OF THE SC UPSTATE...BEFORE
OVERTAKING THE NC PIEDMONT BY EARLY EVENING.  AS PRECIP SLIDES
IN...EXPECTING WETBULB EFFECTS TO ASSIST IN COOLING OF TEMPS THROUGH
THE LOW LEVELS...ALONG WITH GOOD DYNAMIC COOLING DUE TO THE INTENSE
UPWARD MOTION BENEATH ABOVE MENTIONED COUPLED UPPER JET MAXIMA.
THUS...EXPECTING RAIN TO CHANGE OVER TO SNOW ALONG OR JUST SOUTH OF
I85 AROUND THE 6PM TIMEFRAME ACROSS GA/SC...THEN AN HOUR OR SO LATER
OVER NC.  IT IS ALSO AT THIS TIME WHEN IT IS FCST THAT MESOSCALE
BANDING COULD OCCUR YIELDING POSSIBLE SNOWFALL RATES ON THE ORDER OF
1-2 INCHES PER HOUR.  ITS NEARLY IMPOSSIBLE TO DETERMINE EXACTLY
WHERE THIS WILL OCCUR...AS WITH THE RAIN/SNOW LINE...BUT IT LOOKS
THAT THE I85 CORRIDOR IS LIKELY TO BE THE MOST FAVORABLE LOCATION.
AS ALWAYS...DUE TO THE UNCERTAINTY OF ALL THESE FEATURES
ALIGNING...SNOW TOTALS COULD BE GREATLY AFFECTED OVER A SMALL...SAY
30M AREA.  AS FOR SNOW TOTALS...BLENDED IN HPC QPF WITH A TOUCH OF
SREF AND ENDING UP WITH THE HEAVIEST AMOUNTS...IN THE 6-8 INCH RANGE
ALONG AND JUST NORTH OF I85...WITH AMOUNTS TAPERING A BIT FURTHER
NORTH DUE TO PROXIMITY FROM QPF MAXIMA.  SOUTH OF I85 EXPECTING THE
MIXED PTYPE TO POSSIBLY AFFECT SNOW TOTALS SIGNIFICANTLY...WHERE
GENERALLY 3-5 INCHES IS FCST.  SNOW WILL CONTINUE THROUGH THE
OVERNIGHT WITH INTENSITY BACKING OFF AS PRIMARY UPPER FORCING EXITS
EAST.  THUS...POPS REMAIN IN THE LIKELY RANGE UP UNTIL DAYBREAK
THURSDAY WHERE THEY TAPER FROM THE WEST TO CHANCE LEVELS WHERE
POSSIBLE DEFORMATION ZONE COULD ALLOW FOR FURTHER CONTINUATION OF
SNOWFALL.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 330 AM WEDNESDAY...THE SHORT RANGE WILL FOCUS ON THE
AFTERMATH OF OUR WINTER STORM STARTING ON THURSDAY. THE
MODELS...IN PARTICULAR THE NAM...SUGGEST THAT A WEAK DEFORMATION
ZONE MAY TRANSLATE E ACROSS THE WESTERN CAROLINAS AND NE GEORGIA
IN THE EARLY PART OF THE MORNING. WILL HOLD ONTO A CHANCE OF
PRECIP FIRST THING IN THE DAY... AND ALLOW IT TO SLOWLY DROP INTO
THE AFTERNOON. THE PASSAGE OF A FOLLOW-UP WAVE MAY TRIGGER
ADDITIONAL SHOWERS ACROSS THE REGION THROUGH THE AFTERNOON AND
INTO THE EARLY EVENING. EAST OF THE MOUNTAINS...THIS MAY TAKE THE
FORM OF SHALLOW CONVECTION...MOST LIKELY AS RAIN SHOWERS...BUT A
FEW SNOW SHOWERS WILL NOT BE RULED OUT. WITH THE PASSAGE OF THIS
WAVE IN THE LATE AFTERNOON...THE LOW LEVEL FLOW WILL COME AROUND
TO NW AND THAT WILL FORCE THE DEVELOPMENT OF SNOW SHOWERS ON THE
TN BORDER THROUGH THURSDAY NIGHT. EXPECT THE SNOW SHOWERS TO TAPER
OFF FRIDAY BY MIDDAY OR SO AS THE MOISTURE PULLS OUT. TEMPS WILL
BE WELL BELOW NORMAL THURSDAY ACROSS MOST OF THE AREA OWING TO
WHAT SHOULD BE A BLANKET OF NEW SNOW.

THE REST OF THE SHORT RANGE...FRIDAY AND FRIDAY NIGHT...IS
RELATIVELY QUIET. PREFER TO KEEP THE FCST DRY AT THIS POINT. THE GFS
SUGGESTS SOME LOW LEVEL MOISTURE TRAPPED UNDERNEATH AN INVERSION IN
A WEAK EASTERLY FLOW. THIS SUGGESTS WE MIGHT END UP WITH SOME
DRIZZLE OR FREEZING DRIZZLE NEAR THE BLUE RIDGE. WOULD RATHER NOT
INCLUDE A TRACE EVENT FOR NOW. TEMPS WILL REMAIN BELOW NORMAL INTO
THE EARLY PART OF THE WEEKEND.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 225 AM WEDNESDAY...THE MEDIUM RANGE PERIOD STARTS AT 12Z
SATURDAY WITH A PERSISTENT AND VERY BROAD UPPER TROF PATTERN OVER
MOST OF THE CONUS. THE PATTERN SATURDAY MORNING HAS A 1045 SURFACE
HIGH OVER OHIO AND PA DRIFTING SLOWLY EAST.  AS WE MOVE INTO
SUN...THE PATTERN FLATTENS OVER THE SOUTHEAST REGION AS WEAK UPPER
RIDGING TRIES TO BUILD OVER THE GULF OF MEXICO. THE LONG RANGE MODELS
ARE MOSTLY ON THE SAME PAGE AND HAVE THE RIDGE GRADUALLY
STRENGTHENING THRU THE REMAINDER OF THE PERIOD AS A SOUTHERN STREAM
H5 TROF DIGS DOWN OVER THE EXTREME
DESERT SW.

AT THE SFC...AN IMPRESSIVE 1040MB CANADIAN HIGH WILL BE IN PLACE
OVER THE REGION BY EARLY SAT WITH NORTH TO NELY LOW LVL FLOW SETTING
IN OVER THE CWFA. BY EARLY SUN...THE HIGH SLIDES FARTHER EAST WITH
SOME SORT OF CAD PATTERN SETTING UP OVER THE CAROLINAS. BY EARLY
MON...BOTH THE GFS AND ECMWF HAVE THE CAD DISSIPATING AS THE PARENT
HIGH MOVES FARTHER OFFSHORE. BEYOND THIS POINT...THE SFC PATTERN
BECOMES MORE AMBIGUOUS WITH SOME SORT OF BROAD DEFORMATION ZONE
SETTING UP JUST TO OUR NW WITH DEEP LYR MOISTURE OVERSPREADING THE
REGION BY EARLY MON. SIMULTANEOUSLY...ANOTHER HIGH TRACKS EASTWARD
ACROSS THE GREAT LAKES AND IS OVER NEW ENGLAND BY EARLY TUES. THE
MODELS ALSO GENERATE ANOTHER SOUTHERN PLAINS LOW EARLY TUES AND MOVE
ITS ASSOCIATED COLD FRONT TO OUR DOORSTEP BY THE VERY END OF THE
PERIOD. AS FOR THE SENSIBLE WX...SAT SHOULD BE DRY WITH TEMPS
REMAINING BELOW CLIMATOLOGY FOR LATE FEB. THE FCST FOR THE REMAINDER
OF THE PERIOD IS TRICKY. PRECIP CHANCES WILL RAMP UP TO SOLID CHANCE
BY SUN AFTERNOON WITH THE POSSIBILITY OF FROZEN PRECIP EARLIER IN
THE DAY. HIGHS WILL LIKELY REACH THE MID TO UPPER 40S...SO ALL
PRECIP SHOULD TRANSITION TO RAIN LATER IN THE DAY. THE REST OF THE
PERIOD WILL BE CHARACTERIZED BY MOIST PROFILES...MOSTLY OVERCAST
SKIES...AND SOLID CHANCES FOR WIDESPREAD PRECIP THRU THE REST OF THE
PERIOD. TEMPS SHOULD ALSO REBOUND TO ABOVE NORMAL BY EARLY NEXT WEEK
WITH HIGHS IN THE 60S ON BOTH MON AND TUES. SCALED BACK THE POPS
JUST A TAD IN DAY 6 AND 7 DUE TO BEING THE END OF THE FORECAST
PERIOD AND THE DECREASED CONFIDENCE THAT PATTERNS COULD CHANGE SOME
BY THAT TIME.

WELL BELOW NORMAL TEMPS SAT...SLIGHTLY CLOSER TO NORMAL SUNDAY AND
THEN GOING ABOVE NORMAL TEMPS MONDAY AND TUESDAY.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...SIGNIFICANT WINTER WEATHER RESTRICTIONS EXPECTED WITHIN
THIS TAF CYCLE AS POTENT SURFACE WAVE AND ASSOCIATED UPPER SUPPORT
SLIDE THROUGH THE REGION.  TAF INITIALIZES AMIDST MVFR CIGS AND
LIGHT SW FLOW AT THE SFC.  EXPECTING CIG RESTRICTIONS TO LIFT BY
AROUND DAYBREAK ALTHOUGH WITH DECREASED VISB AS LIGHT FOG DEVELOPS
AROUND THE REGION.  WOULD ALSO NOT BE SURPRISED TO SEE SOME FZFG IF
IT BECOMES DENSE ENOUGH AS SURFACE TEMPS WILL BE
SUBFREEZING...ALTHOUGH WAS LEFT OUT OF TAF AT THIS TIME.  AFTER
DAYBREAK CONDITIONS WILL IMPROVE YIELDING THE CALM BEFORE THE STORM
WITH MID/HIGH LEVEL CLOUDS PREVAILING THROUGH MID AFTERNOON.
EXPECTING PRECIP TO ENTER THE REGION LATE DAY IN THE FORM OF A RASN
MIX BEFORE QUICKLY CHANGING OVER TO RAIN.  AT THAT TIME...CIGS/VISB
WILL DROP TO MVFR/IFR...THEN TO LIFR AS HEAVY SNOW SHOWERS MOVE
INTO THE REGION.  OPTED TO INCLUDE RASN MENTION AT 00Z WITH MVFR
CIGS AND IFR VISB BEFORE LOWERING TO LIFR CIGS WITH PREDOMINATE SN
AT 02Z...LASTING THROUGH THE PERIOD.  LATEST ACCUMULATION FCST
INDICATES THAT THE I85 CORRIDOR WILL BE THE MAXIMA THUS WOULD NOT BE
SURPRISED TO SEE MODERATE/HEAVY SNOWFALL AT TIMES WITH RATES
EXCEEDING 1-2 INCHES PER HOUR CAUSING SIGNIFICANT VISB
RESTRICITONS.

AT KAVL AND KHKY...ALSO EXPECTING SIGNIFICANT FLIGHT RESTRICITONS
DUE TO SNOWFALL MOVING INTO THE REGION MID/LATE DAY WEDNESDAY.
INITIALIZED KAVL VFR WHILE GOING WITH IFR CIGS AT KHKY FOR THE NEXT
FEW HOURS BEFORE IMPROVEMENT IS INTRODUCED...ALTHOUGH CONTINUING
WITH MVFR VISB DUE TO LIGHT FOG/MIST.  OTHERWISE...BEYOND DAYBREAK
VFR WILL PREVAIL AHEAD OF PRECIP ARRIVAL BY LATE AFTERNOON IN THE
FORM OF SN.  THE MOST SIGNIFICANT ACCUMULATIONS ARE FCST FURTHER
SOUTH ALONG THE I85 CORRIDOR...HOWEVER WOULD NOT BE SURPRISED TO SEE
MODERATE ACCUMS WITH RATES NEARING 1-2 INCHES PER HOUR CAUSING
SIGNIFICANT VISB RESTRICITONS.

SC SITES...ALL SC SITES WILL BE IMPACTED BY SIGNIFICANT SNOWFALL
THROUGH THIS PERIOD LEADING TO ABUNDANT FLIGHT RESTRICITONS.
INITIALIZED ALL TAFS AT MVFR/IFR DUE TO LINGERING LOW LEVEL MOISTURE
IN THE BL.  THESE CIG CONDITIONS ARE EXPECTED TO IMPROVE THROUGH
MORNING ALTHOUGH GIVING WAY TO DECREASED VISB AT KAND WITH PATCHY
DENSE FOG POSSIBLE AT KGMU/KGSP.  TEMPERATURES WILL REMAIN BELOW
FREEZING THROUGH MORNING THUS FZFG IS A POSSIBILITY...THEREFORE
OPTED TO INCLUDE VIA TEMPO.  VFR WILL PREVAIL THROUGH LATE MORNING
BEFORE PRECIP SLIDES IN FROM THE WEST IN THE FORM OF RASN MIX BEFORE
QUICKLY TRANSITIONING TO ALL SNOW.  AS MENTIONED ABOVE...THE I85
CORRIDOR LOOKS TO BE THE MAXIMA OF EXPECTED SNOWFALL THEREFORE WOULD
NOT BE SURPRISED TO SEE MODERATE/HEAVY SNOWFALL RATES OF AROUND 1-2
INCHES PER HOUR CAUSING SIGNIFICANT VISB RESTRICITONS.

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 WEATHER ADVISORY UNTIL NOON EST TODAY FOR GAZ010-017-
     018-026-028-029.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 7 AM EST
     THURSDAY FOR GAZ010-017-018-026-028.
     WINTER STORM WATCH FROM THIS EVENING THROUGH LATE TONIGHT FOR
     GAZ029.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ033-
     035>037-048>053-056>059-062>065-068>072-082-501>510.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 7 AM EST
     THURSDAY FOR NCZ033-035>037-048>053-056>059-062>065-
     068>072-082-501>510.
SC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR SCZ001>014-
     019.
     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 7 AM EST
     THURSDAY FOR SCZ001>010-012>014.
     WINTER STORM WATCH FROM THIS EVENING THROUGH LATE TONIGHT FOR
     SCZ011-019.

&&

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



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