Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 091150
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
650 AM EST TUE FEB 9 2016

.SYNOPSIS...
A BROAD AND MOIST AREA OF LOW PRESSURE WILL SLOWLY CROSS THE REGION
THROUGH WEDNESDAY NIGHT. CANADIAN HIGH PRESSURE WILL THEN BUILD IN
THURSDAY AND REMAIN THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
630 AM UPDATE...MIDLEVEL CLOUD DECK EXPANDING INTO THE
PIEDMONT...PLENTY COLD ENOUGH TO BE ABLE TO PRODUCE SNOW.
HOWEVER...NO RETURNS ARE SEEN DOWNSTREAM OF THE BLUE RIDGE. BASED
ON LATEST MESO GUIDANCE...STILL EXPECTING ACCUMULATION MORE THAN A
TRACE TO REALLY ONLY BE POSSIBLE IN UPSLOPE AREAS...WITH SEEMINGLY
ONLY VERY LIGHT SNOW /POSSIBLY SNOW GRAINS/ FALLING OVER
ASHEVILLE...FRANKLIN AND BOONE. THE WINTER STORM WARNING WILL BE
ALLOWED TO EXPIRE SHORTLY. THE MESO GUIDANCE IS NOW PICKING UP ON
SOME LIGHT ACTIVITY POSSIBLY DEVELOPING OVER NE GA AND VICINITY
THIS AFTN...PRESUMABLY INVOF CHANNELED VORT MAX COMING DOWN THE
BACK SIDE OF THE TROUGH.

AS OF 315 AM...DEEP UPPER TROUGH WITH EMBEDDED CYCLONE NOW SITS
OVER VIRTUALLY THE ENTIRE EASTERN CONUS. A KINK IN THE CIRCULATION
IS SWINGING ACROSS ERN KY/TN...AND A BROAD AREA OF LIGHT SNOW
EXTENDS FROM NEAR KNOXVILLE TO NEAR PITTSBURGH AHEAD OF IT. SOME
OF THIS MOISTURE AND WESTERLY LLVL FLOW WILL CONTINUE TO INTERCEPT
THE SRN APPALACHIANS THRU THE MORNING. BASED ON THE FEW SFC OBS
AND WEBCAMS AVAILABLE FROM NEAR THE SPINE OF THE MOUNTAINS...THE
ACCUM SINCE SNOW BEGAN YESTERDAY IS GENERALLY UNDER 2 INCHES. PEAK
RATES FROM THIS PHASE OF THE EVENT HAVE ALREADY OCCURRED. THOUGH
SNOW WILL CONTINUE TODAY...WINDS ARE EXPECTED TO BACK AND UPPER
FORCING TO WEAKEN AS THAT SHORTWAVE KINK MOVE EAST OF THE CHAIN...SO
THE UPSLOPE FORCING WILL WEAKEN ACCORDINGLY. SHORT RANGE GUIDANCE
SEEMS TO HAVE PICKED UP ON THIS AS THE CONSENSUS IS THAT RATES WILL
SLOW...AND A LULL IN SNOW WILL OCCUR DURING THE DAY. WINDS BECOME
MORE FAVORABLE AGAIN BY THIS EVENING...AND ANOTHER LOBE OF THE
TROUGH WILL PASS AS WELL PROVIDING A BOOST ALOFT. THUS THE SNOW
SHOULD PICK BACK UP THIS EVENING...THIS ALSO BACKED UP BY SHORT
RANGE GUIDANCE. WHILE I FEEL THE HIGHER-RES GUIDANCE IS DOING A
GOOD JOB WITH THE TRENDS...I AM RELUCTANT TO USE ITS RELATIVELY
HIGH QPF...WHICH WAS OVERDONE MONDAY. WE WILL LET THE WINTER
STORM WARNING EXPIRE AT 12Z AS EXPECTED...THEN HOIST A WINTER
WEATHER ADVISORY FOR THE NC MTNS PLUS RABUN COUNTY...GOING THRU 6
AM TOMORROW. WE WILL KEEP THE WIND CHILL ADVISORY AS-IS GIVEN THE
CONTINUED COLD ADVECTION AND MODEST GRADIENT FLOW STILL POISED TO
BRING WIND CHILLS FROM 5 TO 15 BELOW ZERO IN THE HIGHER ELEVATIONS
BY DAYBREAK WED.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 335 AM TUESDAY...NW FLOW SNOW WILL BEGIN WINDING DOWN WED AS
AS THE MOISTURE AND WIND DIMINISH. COULD SEE ANOTHER HALF INCH IN
THE USUAL LOCATIONS BEFORE THE SNOW SHOWERS TURN MORE TO FLURRIES
THEN END WED NITE. ALTHOUGH WINDS WILL DIMINISH...THEY WILL BE HIGH
ENUF AND TEMPS COLD ENUF FOR HIGH ELEVATION WIND CHILLS TO FALL BACK
INTO THE ADVISORY RANGE. HIGHS ACROSS THE MTNS WILL BE NEAR THE
NORMAL LOWS...AND UP TO 15 DEGREES BELOW NORMAL ELSEWHERE. LOWS WILL
BE 10 TO 15 DEGREES BELOW NORMAL.

A WEAK CLIPPER SYSTEM WILL DROP INTO THE AREA THU AND EAST OF THE
AREA THU NITE. GUIDANCE IS IN DISAGREEMENT ON THE AMOUNT OF MOISTURE
AND ANY RESULTING PRECIP. THEREFORE...HAVE KEPT A DRY FCST FOR NOW
AS EVEN THE WETTEST MODEL DOES NOT HAVE ANY SIGNIFICANT SNOWFALL.
THICKNESSES RISE AHEAD OF THE CLIPPER BRINGING A WARMING TREND
ACROSS THE CWFA. HIGHS WILL /ONLY/ BE 10 TO 15 DEGREES BELOW NORMAL
WHILE LOWS END UP AROUND 10 DEGREES BELOW NORMAL. WITH THE INCREASE
IN TEMPS AND RELATIVELY LIGHT WINDS...WIND CHILL VALUES SHUD REMAIN
ABOVE ADVISORY LEVELS THU NITE.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 355 AM TUESDAY...MUCH BETTER AGREEMENT IN THE MEDIUM RANGE
GUIDANCE THIS MORNING...AT LEAST UNTIL THE END OF THE PERIOD. THE
DEEP ERN CONUS TROF WILL REMAIN IN PLACE THRU SAT. SHORT WAVES
ROTATING THRU THE TROF BRING AN ARCTIC FRONT ACROSS THE AREA WITH A
RETURN OF A VERY COLD AIR MASS. THERE COULD BE SOME LIGHT NW FLOW
SNOW BEHIND THE FRONT...BUT IT LOOKS TO BE LESS THAN ADVISORY LEVEL
SNOWFALL FOR NOW. HIGHS FRI RISE A COUPLE OF DEGREES FROM THU AHEAD
OF THE ARCTIC FRONT...THEN DROP PRECIPITOUSLY THRU SUN BEHIND THE
FRONT. IN FACT...HIGHS SUN WILL BE NEAR THE NORMAL LOWS FOR THIS
TIME OF YEAR...WITH LOWS UP TO 15 TO 20 DEGREES BELOW NORMAL. WITH
THE COLD TEMPS AND INCREASING WINDS BEHIND THE FRONT...VERY LOW WIND
CHILL VALUES WILL RETURN AS WELL. HIGH ELEVATION ADVISORY LEVEL WIND
CHILLS ARE POSSIBLE FRI NITE...WITH WIDESPREAD MTN VALLEY ADVISORY
AND HIGH ELEVATION WARNING LEVEL WIND CHILLS POSSIBLE SAT NITE.

GUIDANCE DISAGREES ON THE POTENTIAL WEATHER SYSTEM MOVING THRU ON
MON. THE GFS HAS A WEAK FRONTAL SYSTEM MOVING THRU FROM THE NW WITH
LITTLE GULF OR ATLANTIC IN FLOW. THE ECMWF HAS A STRONG FRONT MOVING
IN FROM THE WEST WITH STRONG GULF INFLOW. SURFACE AND H85 TEMPS
WOULD INDICATE SOME SNOW POTENTIAL ACROSS THE MTNS AND NRN TIER WITH
MAINLY RAIN ELSEWHERE. HAVE GONE WITH A GUIDANCE BLEND AND KEPT POP
IN THE CHANCE RANGE FOR NOW...WITH THE RAIN/SNOW LINE BASED ON
SURFACE TEMPS. CONFIDENCE IS LOW IN THIS PORTION OF THE FORECAST
WITH CHANGES LIKELY AS IT APPROACHES.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AT KCLT...WITH CYCLONIC UPPER FLOW OVER THE REGION...EXPECT PERIODS
OF MIDLEVEL CIGS THRU THE DAY. WINDS WILL BE DIFFICULT TO NAIL DOWN
THRU MUCH OF THE PERIOD...WITH NEAR DUE WESTERLY FLOW EXPECTED...AND
A COMPLEX PRESSURE PATTERN NOT LENDING MUCH CONFIDENCE TO WSW VS
WNW. FAIRLY GOOD MIDLEVEL LAPSE RATES WILL AGAIN ALLOW CONGESTED
CU TO DEVELOP OVER A DEEP MIXED LAYER...WHICH IS NOT EXPECTED TO
PRODUCE ANY PRECIP THOUGH A FEW BRISK GUSTS MIGHT RESULT. BASES
SHOULD LIFT A BIT GOING INTO EVENING...WITH CLOUDS SCATTERING
AS WELL.

AT KAVL...NW FLOW INTO THE MOUNTAINS WILL CONTINUE TO PRODUCE LOW
CLOUDS AND -SHSN. OCNL RESTRICTIONS DURING MORE INTENSE SHOWERS
CAN/T BE RULED OUT...BUT THAT LOOKS UNLIKELY ENOUGH TO OMIT. LITTLE
TO NO CHANGE IN THE PATTERN IS SEEN THRU THE PERIOD...SO A FEW
FLURRIES MAY BE SEEN MORE OR LESS CONTINUOUSLY...BUT THE CHANCE
OF ACCUMULATION BEYOND A TRACE IS LOW. WINDS STAY NW BUT FREQUENT
GUSTING IS LIKELY IN THE AFTERNOON.

ELSEWHERE EAST OF THE MTNS...SCT-BKN STRATOCU DECKS ARE LIKELY TO
COME AND GO MUCH OF THE PERIOD AS CYCLONIC UPPER FLOW PERSISTS...AND
EMBEDDED EDDIES PROVIDE PERIODIC ENHANCEMENT TO LIFT. DEEP MIXING
AGAIN WILL PERMIT GUSTINESS DURING PEAK HEATING TODAY. WINDS WILL
REMAIN NEAR WEST...WITH SOME VARIABILITY.

OUTLOOK...SEVERAL STRONG UPPER DISTURBANCES EMBEDDED IN A DEEP
UPPER TROUGH WILL SWING ACROSS THE AREA THRU WEDNESDAY. MOISTURE
AND COLD AIR WILL CONTINUE TO FLOW INTO THE AREA DURING THIS
TIME PERIOD. RESTRICTIONS WILL BE POSSIBLE...PARTICULARLY IN THE
MOUNTAINS WHERE THERE ARE HIGH CHANCES OF ACCUMULATING SNOW.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     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 SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR GAZ010.
NC...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR NCZ033-
     048>052-058-059.
     WINTER STORM WARNING UNTIL 7 AM EST THIS MORNING FOR NCZ033-
     048>052-058-059.
     WIND CHILL ADVISORY FROM 7 PM THIS EVENING TO NOON EST
     WEDNESDAY FOR NCZ033-048>052-058-059-062>064.
     WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR NCZ053-
     062-063.
SC...NONE.

&&

$$
SYNOPSIS...RWH/SBK
NEAR TERM...WIMBERLEY
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...WIMBERLEY


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