Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 251759
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1259 PM EST TUE NOV 25 2014

.SYNOPSIS...
A COLD FRONT WILL PUSH THROUGH THE AREA THIS MORNING AND STALL ALONG
THE SOUTHEAST COAST. LOW PRESSURE WILL DEVELOP ALONG THIS FRONT AND
MOVE UP THE ATLANTIC SEABOARD WEDNESDAY. AN UPPER LEVEL SYSTEM WILL
CROSS WESTERN NORTH CAROLINA EARLY THURSDAY. DRY HIGH PRESSURE WILL
RETURN FRIDAY AND LINGER INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 1245 PM EST...WATER VAPOR IMAGERY SHOWS A POSITIVELY TILTED
500 MB TROUGH EMERGING FROM THE PLAINS THIS AFTN. THIS FEATURE WILL
BECOME MORE NEUTRALLY TILTED OVER THE LOWER MS VALLEY TONIGHT AND
THEN ACQUIRE A NEGATIVE TILT AS IT CROSS THE APPALACHIANS WED AND
PHASES BACK INTO THE BROAD TROUGH AXIS FROM THE GREAT LAKES TO THE
GULF COAST. AT THE SFC...A LOW CENTER DEVELOPING ALONG THE FL E
COAST LATE TODAY WILL MOVE RAPIDLY UP THE COASTAL CAROLINAS TONIGHT.
DEEP LAYER FORCING FROM FRONTOGENESIS WILL LIKELY SET UP INTO FAR
INTERIOR PARTS OF THE CAROLINAS...POSSIBLY OVER THE FOOTHILLS. IN
ADDITION...THE BEST UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION OF
THE 250 MB JET STREAK WILL CROSS THE FORECAST AREA FROM THE WEST 09Z
TO 15Z...WHILE DEEP LAYER Q VECTOR CONVERGENCE MAXIMIZES WITH THE
TROUGH OVER WRN NC WED MORNING. THESE FEATURES SHOULD COME TOGETHER
TO PRODUCE SOME SOLID 0.5 TO 0.75 INCH LIQUID EQUIVALENT PRECIP
TOTALS THROUGH MIDDAY WED.

PRECIPITATION TYPE WILL BE A CRITICAL FORECAST FACTOR. PROFILES ALL
HAVE SOME DEGREE OF A SFC WARM LAYER ACROSS THE
PIEDMONT/FOOTHILLS/LOWER MTN VALLEYS. HOWEVER...THE MOST TROUBLING
MODEL TREND IS FAIRLY STRONG 700 MB FRONTOGENESIS THAT APPEARS TO
SET UP OVER THE FOOTHILLS. ALTHOUGH NON MTN PROFILES LOOK JUST WARM
ENOUGH FOR RAIN...ANY HIGHER RATES COULD OVERCOME THE SFC BASED WARM
LAYER AND PRODUCE SNOW SHOWERS AT TIMES OVER THE NC FOOTHILLS AND
THE FAR NW PIEDMONT...AS WELL AS THE LOWER MTN VALLEYS. THE HIGHER
TERRAIN SHOULD BE SOLIDLY SNOW FOR MOST OF THE EVENT. THE EVENTUAL
TRACK OF THE DEEPENING 850 MB LOW CENTER WILL BE CRITICAL. SINCE THE
MODELS HAVE TRENDED JUST WEST OF INTERSTATE 95...THE ASSOCIATED
FORCING FOR RA/SN SHOWERS WILL BE PUSHED WEST INTO THE
FOOTHILLS...WITH CORRESPONDING SLIGHTLY HIGHER QPF/SNOW TOTALS ALONG
AND JUST E OF THE BLUE RIDGE. SOME ADJUSTMENTS TO THE CURRENT HAZARD
SUITE ARE LIKELY PENDING COLLABORATION WITH THE NEIGHBORS. EXPECT A
SLIGHT EXPANSION.

A LULL IN ACTIVITY IS EXPECTED BETWEEN UPPER WAVES WED AFTN ALONG
WITH BRIEF DEEPER LAYER DRYING. HOWEVER...LOW LEVEL NW FLOW MOISTURE
MAY CONTINUE TO WRING OUT SCATTERED NRN/WRN MTN SNOW SHOWERS WELL
INTO THE AFTN. WILL TRIM MIN AND MAX TEMPS BELOW
GUIDANCE...ESPECIALLY IN NRN SECTIONS...TONIGHT/WED.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUE...SFC LOW WILL CONTINUE TO LIFT UP THE EAST COAST
LATE WED WITH THE AXIS OF THE LONGWAVE UPPER TROUGH REACHING THE SRN
APPALACHIANS AROUND 06Z THU. EMBEDDED WITHIN IS A CLIPPER SHORTWAVE
WHICH SHOULD PROVIDE A BURST OF OMEGA CONCURRENT WITH DEEP LAYER
SATURATION. THUS...WHILE NEARLY ALL OF THE PIEDMONT WILL SEE PRECIP
END WED AFTN...THERE LOOKS TO BE ONLY A BRIEF LULL IN THE MTNS BEFORE
THE ARRIVAL OF THE CLIPPER. A PERIOD OF DYNAMICALLY DRIVEN
PRECIP...MAINLY SNOWFALL...IS EXPECTED IN THE MTNS AT THIS TIME.
HOWEVER IN THE WAKE OF THE WAVE THE FLOW WILL VEER TO NW...ALLOWING
LIGHT OROGRAPHIC SNOWFALL TO CONTINUE THRU THURSDAY NIGHT.

TEMPS DURING WED AFTN WILL BE WARM ENOUGH FOR RAIN THROUGHOUT THE
CWFA BUT WILL DIP NEAR OR BELOW FREEZING DIURNALLY IN THE EARLY
EVENING. SIMULTANEOUSLY...JUST AHEAD OF THE INCOMING WAVE...THE GFS
AND PARTICULARLY THE NAM SHOW A BRIEF PERIOD OF SOUTHERLY LLVL FLOW
AND WAA AROUND 900 MB. THIS MAY LEAD TO THE DEVELOPMENT OF A SMALL WARM
NOSE AND COULD ALLOW SLEET OR FREEZING RAIN TO BRIEFLY OCCUR IN SOME
OF THE HIGHER ELEVATIONS. HOWEVER BY THE TIME THE DEEPER MOISTURE ARRIVES
AND RATES PICK UP THE FLOW SHOULD HAVE VEERED AGAIN AND NEUTRAL TO
COLD ADVECTION WILL AGAIN LEAD TO ALL-SNOW PROFILES WHICH PERSIST
THRU WED NIGHT. THE CONTINUING NW FLOW ACTIVITY LOOKS TO CHANGE TO
RAIN IN THE LOWER ELEVATIONS THU BEFORE CHANGING BACK TO ALL SNOW FOR
THU NIGHT. WHILE THE MOISTURE PROFILES AND WINDS REMAIN STEADILY
FAVORABLE THRU THURSDAY THE MOISTURE BECOMES AN ISSUE THU NIGHT WHEN
ACCUMULATIONS SHOULD BECOME MINIMAL.

TEMPS REMAIN BELOW CLIMO THRU THURSDAY...THOUGH SOME REBOUND WILL BE
NOTED OUTSIDE THE NW FLOW AREAS ON THU UNDER DOWNSLOPING WINDS AND
MOSTLY CLEAR SKIES. THE CONTINUED COLD ADVECTION HOWEVER WILL ALLOW
THICKNESSES TO CONTINUE DROPPING THU NIGHT...AND BRING LOWS INTO THE
20S ACRS MOST OF THE AREA FRI MRNG.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 330 AM TUE...LITTLE CHANGE FROM THE PREVIOUS FORECAST FOR
THE MEDIUM RANGE. DRY HIGH PRESSURE WILL PREVAIL ACRS THE SOUTHEAST
FRI IN THE WAKE OF THE DEPARTING UPPER TROUGH. THIS HIGH SETS UP
OFFSHORE SATURDAY AS THE UPPER FLOW BECOMES ESSENTIALLY ZONAL. A
POTENT NRN STREAM LOW WILL MOVE ACRS ONTARIO AND QUEBEC SAT NIGHT
INTO SUNDAY PULLING A COLD FRONT INTO THE OHIO VALLEY. SWLY RETURN
FLOW WILL RETURN ENOUGH MOISTURE INTO THE AREA OVER THE WEEKEND THAT
BY SUNDAY SCHC POPS RETURN TO THE SW MTNS. POPS SLOWLY RETURN OVER
MORE OF THE AREA THRU EARLY NEXT WEEK AS THE COLD FRONT SAGS IN FROM
THE NORTH. GIVEN THE WARM SFC FLOW...TEMPS WILL MODERATE TO NEAR
CLIMO BY LATE WEEKEND.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...THE LOW LEVEL DRYING BEHIND THE FRONT HAS PROBABLY REACHED
IT/S EASTWARD EXTENT. WE SHOULD NOW SEE MOISTURE GRADUALLY FILLING
BACK IN FROM THE TOP DOWN...WITH MAINLY MID LEVEL VFR CIGS BECOMING
LOWER VFR STRATOCUMULUS BY EVENING. MOISTURE WILL RETURN IN EARNEST
THIS EVENING AS LOW PRESSURE DEEPENS ALONG THE SC COAST. ALL MODEL
AND ENSEMBLE PROFILES FOR THE OVERNIGHT HOURS INDICATE ENOUGH OF A
SFC BASED WARM LAYER TO KEEP THE HEAVIEST PRECIPITATION LIQUID
OVERNIGHT INTO WED MORNING. THE ONLY CONCERN IS THAT FRONTOGENESIS
COULD CREATE SOME BANDED PRECIP TOWARD DAYBREAK THAT MIGHT PUSH SNOW
LEVELS BRIEFLY DOWN INTO THE FOOTHILLS...BUT THIS IS NOT EXPECTED TO
REACH KCLT. NE WINDS WILL TURN SLOWLY N THEN NW THROUGH THE PERIOD.
A FEW LOW END GUSTS ARE POSSIBLE TOWARD DAYBREAK. SOLID IFR CIGS
THROUGH THE EARLY MORNING HOURS COULD IMPROVE A BIT TOWARD THE END
OF THE PERIOD...BUT WILL NOT INCLUDE THAT WITH THIS ISSUANCE.

ELSEWHERE...SOLID MID LEVEL CIGS WILL STEADILY LOWER THROUGH THE
AFTERNOON HOURS...WITH LOWER VFR STRATOCUMULUS ARRIVING FROM THE S
BY EARLY EVENING. THE LIGHT RAIN SHOULD FOLLOW QUICKLY BEHIND THAT
AS MOISTURE AND FRONTOGENESIS DEEPEN FROM THE COASTAL LOW. EXPECT
SNOW LEVELS TO FALL ACROSS THE HIGHER TERRAIN...WITH KAVL SEEING
MAINLY SNOW BY 09Z. THE FRONTOGENESIS MAY BE STRONG ENOUGH ACROSS
THE FOOTHILLS TO PUSH SNOW LEVELS DOWN TOWARD KHKY BY 09Z. THE SC
TAF SITES SHOULD HAVE A DEEP ENOUGH SFC WARM LAYER TO REMAIN ALL
LIQUID. EXPECT MVFR CIGS LATER THIS EVENING TO TRANSITION DOWN
QUICKLY TO IFR OVERNIGHT. SOME LIFR IS POSSIBLE AT TIMES...BUT WILL
STAY WITH THE CONSENSUS OF MOS AND KEEP CONDITIONS LOWER END IFR ALL
BUT KHKY. GRADUAL IMPROVEMENT TO MVFR IS LIKELY LATE IN THE PERIOD
FROM THE SW AS THE PRECIPITATION PULLS AWAY. EXPECT NRLY SFC WINDS
TO BECOME MORE NW WITH TIME.

OUTLOOK...ANOTHER ROUND OF SCATTERED RAIN SHOWERS SOUTH AND
RAIN/SNOW SHOWERS NORTH WILL IMPACT THE AREA WED NIGHT INTO THU
MORNING. A DRY AIR MASS WILL THEN RETURN TO THE AREA THROUGH THU
NIGHT THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       MED   78%     HIGH  82%     MED   78%     MED   79%
KGSP       HIGH 100%     HIGH  89%     HIGH  81%     HIGH  80%
KAVL       HIGH 100%     HIGH  94%     HIGH  82%     HIGH  88%
KHKY       HIGH 100%     HIGH  95%     HIGH  82%     MED   69%
KGMU       HIGH 100%     HIGH  89%     HIGH  86%     MED   78%
KAND       HIGH 100%     HIGH  95%     MED   79%     HIGH  80%

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 STORM WARNING FROM 9 PM THIS EVENING TO 4 PM EST
     WEDNESDAY FOR NCZ033.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON EST
     WEDNESDAY FOR NCZ052-053-059-064.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 4 PM EST
     WEDNESDAY FOR NCZ049-050.
SC...NONE.

&&

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



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