Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 251937
AFDGSP

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

.SYNOPSIS...
LOW PRESSURE WILL DEVELOP ALONG A STALLED COLD FRONT OFF THE
ATLANTIC SEABOARD TONIGHT AND MOVE UP THE COAST 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 225 PM EST...A FEW WINTER WEATHER WARNING/ADVISORY ADJUSTMENTS
ARE BEING MADE. THE WINTER STORM WARNING IS BEING EXPANDED SLIGHTLY
TO ENCOMPASS AVERY/MITCHELL/YANCEY. THE ADVISORY TIER HAS ALSO BEEN
EXPANDED TO THE ERN SLOPES OF THE NRN BLUE RIDGE AND ALSO A BIT
FARTHER INTO THE CENTRAL AND SRN NC MTNS.

WATER VAPOR IMAGERY SHOWS A POSITIVELY TILTED 500 MB TROUGH EMERGING
FROM THE PLAINS. THIS FEATURE WILL BECOME MORE NEUTRALLY TILTED OVER
THE LOWER MS VALLEY TONIGHT AND THEN ACQUIRE A NEGATIVE TILT AS IT
CROSSES THE APPALACHIANS WED AND PHASES BACK INTO THE BROADER TROUGH
TO THE WEST OF THE APPALACHIANS. AT THE SFC...A LOW CENTER
DEVELOPING ALONG THE FL E COAST LATE TODAY WILL MOVE RAPIDLY UP THE
COASTLINE OF THE 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 TONIGHT
THROUGH WED MORNING. MOST MODELS HAVE SLIGHTLY MORE QPF...BUT
COASTAL CONVECTION COULD BE A LIMITING FACTOR IN CAPPING TOTALS.

REGARDING PTYPES...MODEL PROFILES ALL HAVE SOME DEGREE OF A SFC WARM
LAYER ACROSS THE PIEDMONT...FOOTHILLS...AND 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 THROUGHOUT...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. FOR THIS REASON...AN ERN ESCARPMENT EXPANSION OF THE
WINTER WEATHER ADVISORY HAS BEEN ADDED. THE NRN MTN FORECAST TEETERS
ON WARNING CRITERIA...BUT SINCE AVERY IS ALREADY IN SEE NO REASON TO
NOT ADD YANCEY/MITCHELL FOR SOME 4 PLUS INCH ACCUMULATIONS OVER AT
LEAST THE ERN HALF OF THESE COUNTIES. ADDITIONAL LOW END ADVISORY
NUMBERS ARE EXPECTED A BIT FARTHER SW IN THE MTN...MAINLY AT HIGHER
ELEVATIONS...BUT THE BRIEF DURATION OF THE EVENT AND THE MARGINALLY
COLD TEMPS SHOULD PRECLUDE ANY WARNING AMOUNT/SIGNIFICANT TRAVEL
PROBLEMS THERE.

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 FRIDAY/...
AT 230 PM EST TUESDAY...ON WEDNESDAY EVENING AN UPPER TROUGH AXIS
WILL EXTEND FROM HUDSON BAY TO THE EASTERN GULF OF MEXICO. A STRING
CHANNELED VORT LOBE ROUNDING THE BASE OF THE TROUGH WILL BE
APPROACHING THE SOUTHERN APPALACHIANS. THE VORT LOBE CROSSES OUR
AREA EARLY THURSDAY...WHILE THE DEAMPLIFYING TROUGH PROGRESSES TO
THE EASTERN SEABOARD. BY FRIDAY THE UPPER TROUGH MOVES OFF THE EAST
COAST...AND FLOW ALOFT BECOMES MORE ZONAL.

AT THE SURFACE...A WEAKENING LOW WILL MOVE FROM THE LOWER OH RIVER
VALLEY...ACROSS THE SOUTHERN APPALACHIANS ON WEDNESDAY NIGHT.
MOISTURE AHEAD OF THIS SYSTEM WILL MOVE NE ACROSS OUR AREA...
GENERALLY TO THE NW OF INTERSTATE 85. THICKNESS VALUES ARE RATHER
LOW AT THIS TIME...SUPPORTING MAINLY WINTRY PRECIPITATION TO START
WITH IN THE MOUNTAINS. PREVIOUS MODEL RUNS LACKED A WARM NOSE
ALOFT...BUT MORE RECENT RUNS HAVE A BRIEF WARM NOSE AHEAD OF THIS
LOW. THIS COULD RESULT IN SOME BRIEF FREEZING RAIN IN SOME PORTIONS
OF THE SOUTHWEST NC MOUNTAINS WEDNESDAY EVENING...BUT OVERALL...
PRECIPITATION SHOULD BE IN THE FORM OF SNOW IN THE NC
MOUNTAINS...WITH RAIN TO THE EAST. MODEL SOUNDINGS DO LOWER THE
FREEZING LEVEL LATE WEDNESDAY NIGHT AND EARLY THURSDAY ALONG
INTERSTATE 40...TO THE POINT WHERE SNOW MAY MIX IN WITH RAIN...BUT
SURFACE TEMPERATURES AROUND SIX DEGREES BELOW NORMAL ARE ONLY
MARGINALLY SUPPORTIVE OF SNOWFALL ACCUMULATIONS. AT THIS
POINT...MOUNTAIN SNOWFALL ACCUMULATIONS APPEAR TO FALL SHORT OF
ADVISORY CRITERIA.

BEHIND THE SURFACE LOW...SOME LINGERING NW FLOW SNOW SHOWERS WILL
PERSIST AT HIGHER ELEVATIONS INTO THURSDAY...WHILE LOWER ELEVATIONS
OF THE MOUNTAINS CHANGE OVER TO RAIN. THE EVENT IS EXPECTED TO WIND
DOWN QUICKLY THURSDAY EVENING. GUSTY NE WINDS WILL DELIVER ENOUGH
COLD ADVECTION TO OVERCOME DOWNSLOPE WARMING AND BRING TEMPERATURES
TO AROUND 10 DEGREES BELOW NORMAL ON THURSDAY AND THURSDAY NIGHT.
GUSTY WINDS ABATE ON FRIDAY AS A SURFACE HIGH MOVES OVER THE
AREA....WHILE HIGH TEMPERATURES REMAIN ABOUT 10 DEGREES BELOW NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...QUASI-ZONAL 500 MB FLOW ACRS THE CONUS TO
START OUT THE MEDIUM RANGE 00Z SAT...THEN A GRADUAL
AMPLIFICATION...WITH ONE TROF SWEEPING ACRS THE GREAT LAKES...AND
ANOTHER ENTERING THE WEST COAST OVER THE WEEKEND. UPPER RIDGING WILL
PERSIST ACRS THE SOUTHEAST STATES...ALBEIT FAIRLY FLAT. AT THE
SFC...A MODERATING HIGH PRES WILL SETTLE ACRS THE CAROLINAS...GA AND
FL. WITH PERSISTENT WESTERLY 850 MB AND INCREASING
THICKNESSES...EXPECT TEMPS TO REBOUND FROM A COUPLE CATEGORIES BELOW
NORMAL SATURDAY...TO 2-3 CATEGORIES ABOVE NORMAL BY MONDAY. THE
ECMWF AND GFS CONTINUE TO DISAGREE ON HOW BULLISH A BACKDOOR COLD
FRONT IS IN PUSHING SOUTH THRU THE AREA MONDAY NIGHT THRU TUESDAY.
THE 12Z/25 ECMWF IS STRONGER WITH A SFC HIGH AS IT SLIDES INTO THE
NORTHEAST STATES...AND KEEPS MORE MOISTURE ATOP A WEDGE DURING THE
DAY ON TUESDAY. THE GFS KEEPS THE FRONT AND MOISTURE MAINLY NORTH OF
THE AREA THRU TUESDAY NIGHT. I WENT WITH THE 12Z HPCGUIDE...WHICH
WAS BASED ON ECWMF ENS...WHICH IS NOT AS BULLISH AS THE OP
ECWMF...BUT DOES INCREASE CLOUDINESS AND BRING SLIGHTLY COOLER TEMPS
ON TUESDAY. OTHERWISE...EXPECT GENERALLY CLEAR TO PARTLY CLOUDY
SKIES AND DRY CONDITIONS. SOME SLGT TO LOW-END CHC POPS WILL EXIST
ALONG THE TN BORDER...AS MOISTURE IS LIFTED WITH PERSISTENT WESTERLY
UPSLOPE FLOW...SUNDAY THRU TUESDAY.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
AT KCLT...THE LOW LEVEL DRYING BEHIND THE FRONT HAS ABRUPTLY ENDED
AND A FEW PATCHES OF LOWER VFR/HIGH END MVFR CLOUDS ARE FLOATING
AROUND IN THE PIEDMONT. THIS SHOULD PROVIDE TEMPO CIGS AT BEST
THROUGH LATE DAY...WITH MAINLY MID LEVEL VFR CIGS BECOMING LOWER VFR
STRATOCUMULUS BY EVENING. MOISTURE WILL THEN 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 THU NIGHT
THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       MED   75%     HIGH  88%     MED   78%     MED   76%
KGSP       HIGH 100%     HIGH  88%     HIGH  80%     MED   76%
KAVL       HIGH 100%     HIGH  93%     HIGH  88%     HIGH  84%
KHKY       HIGH 100%     HIGH  95%     HIGH  80%     MED   66%
KGMU       HIGH 100%     HIGH  88%     HIGH  83%     MED   73%
KAND       HIGH 100%     HIGH  95%     MED   75%     HIGH  84%

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 9 PM THIS EVENING TO 4 PM EST
     WEDNESDAY FOR NCZ501-503-505.
     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 4 PM EST
     WEDNESDAY FOR NCZ033-049-050.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON EST
     WEDNESDAY FOR NCZ048-051>053-059-063-064.
SC...NONE.

&&

$$
SYNOPSIS...RWH
NEAR TERM...HG
SHORT TERM...JAT
LONG TERM...ARK
AVIATION...HG



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