Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 230253
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
953 PM EST THU JAN 22 2015

.SYNOPSIS...
A DEVELOPING AREA OF LOW PRESSURE WILL TRACK ALONG THE GULF AND
SOUTH ATLANTIC COASTS THROUGH FRIDAY NIGHT...BEFORE MOVING UP THE
EAST COAST OVER THE WEEKEND. THE LOW WILL BRING WIDESPREAD
PRECIPITATION OVER OUR AREA FRIDAY INTO SATURDAY. HIGH PRESSURE WILL
BRIEFLY BUILD IN ON SUNDAY...BEFORE A COLDER LOW PRESSURE SYSTEM
AFFECTS THE FORECAST AREA SUNDAY NIGHT THROUGH TUESDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 945 PM EST...THE LEADING EDGE OF LIGHT PRECIPITATION FALLING
FROM MID LEVEL CLOUD BASES IS APPROACHING THE CWFA FROM THE SW LATE
THIS EVENING...AND THE ONSET OF POP HAS BEEN ACCELERATED FOR THE
NIGHTTIME HOURS. NO CHANGES WILL BE MADE TO THE ADVISORY AREA SINCE
THE LATEST RAP AND INCOMING 00Z NAM PROFILES LOOK VERY SIMILAR TO
THE PREVIOUS MODEL RUNS.

OTHERWISE...WATER VAPOR IMAGERY CONTINUES TO SHOW THE MAIN DRIVING
UPPER LOW MOVING INTO W TX LATE THIS EVENING...WITH SFC DEVELOPMENT
CONTINUING ALONG THE WRN GULF COAST AHEAD OF THIS FEATURE. DEEPER
LAYER MOISTURE AND RAPIDLY INCREASING ISENTROPIC LIFT WILL START
SPREADING INTO THE EXTREME SW SECTIONS 09Z TO 12Z...SPREADING
CATEGORICAL LIGHT TO MODERATE PRECIPITATION COVERAGE ACROSS THE
REGION THROUGH MIDDAY. MEANWHILE...1030 MB SFC HIGH PRES CONTINUES
TO LAY OVER TO THE N OF THE AREA...WITH CHILLY LOW LEVEL
THICKNESSES AND DRIER AIR PARKED ACROSS WRN NC. MODEL PROFILES FROM
ASHEVILLE TO W OF HICKORY TO NEAR BOONE SUPPORT SNOW AT ONSET
OVERNIGHT...WITH WET BULB PROFILES ISOTHERMAL NEAR ZERO. SOME DEGREE
OF WARM NOSING IS EXPECTED TO DEVELOP FRI MORNING...WITH A STEADY
TRANSITION TO SLEET THROUGH MID MORNING AND THEN BRIEF FREEZING RAIN
LINGERING ACROSS THE NRN BLUE RIDGE INTO THE AFTERNOON. PROFILES
SUPPORT MAINLY LIQUID ACROSS SC...NE GA...AND THE NC
PIEDMONT...ALTHOUGH BRIEF SLEET AT THE ONSET WILL BE POSSIBLE JUST
ABOUT ANYWHERE.

THE TRANSIENT NATURE OF THE WINTRY PTYPES ACROSS THE NC MTNS WILL
LIKELY WORK TO KEEP ANY ONE PTYPE FROM REACHING WARNING CRITERIA.
THE CURRENT ADVISORY SUITE REMAINS WELL PLACED...WITH LIGHT SNOW AND
ICE ACCUMULATIONS FRI...WITH A TRANSITION TO ADDITIONAL LIGHT NW
FLOW SNOW ACCUMULATIONS INTO FRI NIGHT. WILL KEEP TEMPS NEAR RAW
MODEL VALUES...WITH A BRIEFLY GUSTY NE FLOW POSSIBLE EAST OF THE
MTNS AS A BARRIER JET FORMS DESPITE THE WEAK DAMMING HIGH POSITION.
PRECIP RATES WILL LIKELY START TO SLACKEN FROM THE SW VERY LATE IN
THE DAY AS WEAK MID LEVEL DRYING BEGINS TO WORK BACK IN.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM THURSDAY...THE SHORT TERM PICKS UP AT 00Z
SATURDAY...WITH MODELS IN GOOD AGREEMENT ON THE SFC LOW CENTERED
INVOF TALLAHASSEE FL...WITH A SHARP H5 TROF AXIS ACRS THE LWR MS
VALLEY. FRIDAY EVENING LOOKS LIKE A CONTINUED TRANSITION TO ALMOST
ALL RAIN ACRS THE CWFA...AS LLVL FLOW TURNS FROM SE TO SW...AND A
DRY SLOT PUNCHES INTO THE SRN APPALACHIANS FROM THE SW. TEMPS MAY BE
ABLE TO HOLD AROUND 30-32 ALONG THE ERN SLOPES OF THE NRN NC BLUE
RIDGE. HOWEVER...ADDITIONAL ICE ACCUMS SHUD BE VERY LIGHT...WITHIN A
LULL IN PRECIP. BY 12Z SAT...A DEFORMATION ZONE WITHIN THE MID LVL
TROF WILL ENTER THE NC MTNS...BRINGING FALLING MID LVL HEIGHTS (AND
SNOW LEVELS)...WHILE INCREASING THE POP. TAKING A BLEND OF THE
NAM/SREF WITH THE WPC QPF (THROWING OUT THE GFS)...I GET 1-2" OF
ADDITIONAL SNOW ACCUM MAINLY ABOVE 3500 FT SATURDAY MORNING. THE
DEFORMATION ZONE WILL TRANSLATE EAST QUICKLY...WITH POPS TAPERING
OFF BY MIDDAY. BY SATURDAY AFTN...NWLY 850 MB FLOW WILL
INCREASE...KEEPING A SLGT CHC TO LOW-END CHC OF SNOW SHWRS ALONG THE
TN/NC BORDER. GRADUAL CLEARING IS EXPECTED EAST OF THE MTNS. TEMPS
WILL HOVER IN THE 30S ACRS THE AREA FRIDAY NIGHT TO NEAR 40 IN THE
UPR SAVANNAH VALLEY...THEN WARM LITTLE ABOVE 3500 FT...BUT INTO THE
MID-UPR 40S ACRS THE PIEDMONT ON SATURDAY.

SATURDAY NIGHT AND SUNDAY...A BROAD H5 TROF WILL LINGER IN WAKE OF
THE SATURDAY TROF PASSAGE. THE CWFA WILL BE IN BETWEEN A NOREASTER
AFFECTING THE MID ATLANTIC/NEW ENGLAND...AND A CLIPPER THAT WILL BE
DIVING INTO THE WRN GREAT LAKES. ANOTHER VORT MAX WILL CROSS THE NC
MTNS SATURDAY NIGHT WITHIN THE LONGWAVE TROF. IT WILL HAVE LITTLE
MOISTURE TO WORK WITH...BUT THE NAM AND GFS BOTH SHOW A HUNDREDTH OR
TWO OF QPF RESPONSE ALONG THE TN/NC NWLY FLOW UPSLOPE AREAS. I
BUMPED UP POPS BACK TO CHC SATURDAY NIGHT FROM MADISON TO AVERY
COUNTY FOR SNOW SHWRS. LITTLE OR NO ACCUMS ARE EXPECTED. THE LLVL
FLOW WILL BACK TO W-SWLY ON SUNDAY...AND GUIDANCE IN GOOD AGREEMENT
ON A DRY DAY ACRS THE CWFA AHEAD OF THE APPROACHING CLIPPER SYSTEM.
TAKING A MODEL BLEND...I GET NEAR NORMAL TEMPS UNDER PARTLY CLOUDY
SKIES.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 200 PM THU...LONGWAVE TROUGH PERSISTS OVER THE ERN CONUS THRU
THE MOST OF THE MEDIUM RANGE. THE UPPER PATTERN IS INITIALLY LOCKED
IN PLACE BY A REX BLOCK OVER THE WEST COAST...WHICH BREAKS DOWN
MONDAY. GLOBAL MODELS DIFFER IN HOW THE PATTERN SUBSEQUENTLY EVOLVES
OVER THE WEST BUT AGREE RIDGING WILL OCCUR OVER THE EAST BY WED
NIGHT. WHILE THE ERN TROUGH REMAINS IN PLACE...A SERIES OF CLIPPER-
LIKE SHORTWAVES WILL MOVE ACROSS OUR AREA. MEAN NWLY FLOW WILL
CONTINUE...SUGGESTING A CONTINUED FOCUS FOR PRECIP CHANCES ALONG THE
WRN FACING SLOPES OF THE NC MTNS. THE PASSING SHORTWAVES APPEAR
CAPABLE OF FORCING VERY LIGHT PRECIP OVER THE PIEDMONT...MAINLY THE
NC SIDE. DOWNSLOPING WILL BE WORKING AGAINST SAID FORCING AND ONLY
LOW POPS AND QPF WILL BE ADVERTISED THERE. IN THE MTNS...BLENDED QPF
FROM THE GLOBAL MODELS AND AN EXPECTATION OF PREDOMINANTLY SNOW AS A
PTYPE SUGGEST TOTALS GENERALLY 1-2 INCHES IN THE 12 HR PERIODS
SUNDAY NIGHT AND MONDAY.  THIS MAY WARRANT A WINTER WX ADVY.

THE 22/12Z GFS CONTINUES TO EXHIBIT A COUPLE OF KEY DIFFERENCES FROM
THE CORRESPONDING GEM OR EC. THE FIRST IS IN THE WELL DEFINED
SHORTWAVE CROSSING THE AREA MONDAY...WHICH DOES NOT COME AS FAR SOUTH
ON THE GFS PROGS AND IS FOLLOWED BY A SECONDARY CHANNELED AREA OF
VORT. THE EC DEPICTS A MORE BROAD TROUGH WITH DISTINCT EDDIES DARTING
THROUGH WITHIN. THE EC BRINGS ANOTHER WAVE OF LIGHT QPF INTO THE AREA
TUESDAY AS A RESULT...WHEN TEMPS HAVE COOLED TO BECOME A LITTLE MORE
SUPPORTIVE OF WINTRY PRECIP. THE GEM LOOKS MORE LIKE THE EC THAN THE
GFS BUT DOES NOT RESPOND WITH QPF TUE. RUN-TO-RUN CONSISTENCY IS NOT
THAT GREAT FOR ANY OF THE MODELS WITH THE SMALLER SCALE WAVES AND
ASSOCIATED QPF. WITH THIS PACKAGE THE PIEDMONT POPS HAVE BEEN
EXPANDED SLIGHTLY THRU EARLY TUE ON ACCOUNT OF CONTINUED HINTS AT
PRECIP.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
AT KCLT...ANTICIPATE LOWERING VFR CIGS OVERNIGHT AHEAD OF THE
APPROACHING GULF COAST LOW PRESSURE SYSTEM. LIGHT RAIN WILL SPREAD
IN FROM THE SOUTHWEST ON THE STRENGTH OF EARLY UPGLIDE 12Z TO
14Z...WITH CIGS LIKELY REACHING MVFR LEVELS AT THAT TIME. SOME SLEET
COULD EASILY MIX IN RIGHT AT ONSET...BUT WITH ALL LIQUID PTYPES
SETTING UP VERY QUICKLY THEREAFTER. ANTICIPATE THE DEEPEST MOISTURE
AND FORCING PRODUCING MODERATE RAINFALL THROUGH FRI
AFTERNOON...ALONG WITH SOLID IFR CONDITIONS DEVELOPING. WINDS WILL
BECOME ENE TO NE THIS EVENING AND STEADILY STRENGTHEN THROUGH FRI.

ELSEWHERE...PRECIPITATION WILL SPREAD IN FAIRLY RAPIDLY FROM THE
SOUTHWEST 10Z TO 13Z FRIDAY...WITH VFR CIGS QUICKLY DIPPING TO MVFR
THROUGH MID MORNING. MORE SOLID IFR CONDITIONS WILL THEN DEVELOP
THROUGH FRIDAY...WITH MAINLY RAIN AT THE UPSTATE TAF SITES...SNOW
AND SLEET CHANGING TO RAIN AT KAVL...AND BRIEF ONSET SLEET AT KHKY
BECOMING ALL RAIN THROUGH THE DAY. EXPECT STRENGTHENING NE
FLOW...EXCEPT NW WINDS AT KAVL EARLY TURNING SE THROUGH FRI. SOME
BRIEF ONSET SLEET CANNOT BE RULED OUT AT THE SC TAF SITES AS
WELL...BUT RAIN SHOULD BE PREDOMINANT.

OUTLOOK...PRECIPITATION AND RESTRICTIONS CONTINUE FRIDAY NIGHT
BEFORE DIMINISHING FROM THE SW ON SAT. ANOTHER SYSTEM ARRIVING SUN
NIGHT INTO MONDAY COULD BRING MORE RESTRICTIONS OVER THE
MTNS...MAINLY NEAR THE TN BORDER THROUGH MONDAY NIGHT.

CONFIDENCE TABLE...

            03-09Z        09-15Z        15-21Z        21-00Z
KCLT       HIGH 100%     HIGH 100%     MED   68%     MED   70%
KGSP       HIGH 100%     HIGH 100%     MED   77%     HIGH  90%
KAVL       HIGH 100%     HIGH 100%     MED   79%     HIGH  86%
KHKY       HIGH 100%     HIGH 100%     MED   73%     HIGH  83%
KGMU       HIGH 100%     HIGH 100%     MED   75%     HIGH  90%
KAND       HIGH 100%     HIGH  98%     HIGH  88%     HIGH  90%

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...WINTER WEATHER ADVISORY FROM 6 AM FRIDAY TO NOON EST SATURDAY
     FOR NCZ033-048>052-058-059-062>064-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...HG
SHORT TERM...ARK
LONG TERM...WIMBERLEY
AVIATION...HG



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