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/...
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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.
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&& .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/...
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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
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&& .GSP WATCHES/WARNINGS/ADVISORIES...
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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.
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&& $$ SYNOPSIS...RWH/SBK NEAR TERM...WIMBERLEY SHORT TERM...RWH LONG TERM...RWH AVIATION...WIMBERLEY

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