Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 070856 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 356 AM EST Wed Dec 7 2016 .SYNOPSIS... A drying trend will continue for several days as high pressure eases into the area. A reinforcing cold front will arrive tonight and early Thursday, bringing the coldest airmass so far this season into the area. High and low temperatures well below normal will persist Thursday night through Saturday before a moderating trend commences early next week when the next cold front arrives. && .NEAR TERM /THROUGH TONIGHT/... As of 230 AM EST Wednesday: Low pressure that brought us all the rain yesterday continues to push east with strong WSW flow aloft over us. Plentiful low level moisture remains in place across the area and with light winds at the surface this has created a perfect environment for fog and low clouds, with visibilities 1/4 mile or less for many sites across the Piedmont. Went ahead and issued a Dense Fog Advisory for all the NC/SC/GA Piedmont, even though technically not ALL the areas meet criteria, it`s close enough and the fog continues to expand. Fog should burn off quickly later this morning with temperatures rebounding to seasonal normals. Meanwhile, the next weather-maker in the form of a strong upper low will be sliding east across the U.S./Canada border, with a very strong and very cold Arctic high diving into the High Plains late today. The front ahead of the high isn`t really all that wet and with each run they`ve trended drier. WPC doesn`t even bring any QPF into the forecast area anymore, but for the sake of consistency did blend in a little from the previous run (what`s 0.01" among friends?). What little moisture there is associated with the front will all get squeezed out over the mountains (though the rest of us could see an increase in clouds overnight tonight). It`ll be cold enough that the higher elevations will likely see some snow showers or at least flurries, but again just not enough moisture for any accumulations. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 200 AM EST Wednesday...A broad upper trough will drift east across the Ohio Valley to the Mid-Atlantic coast Thursday thru Friday. This trough will bring a strong, but rather dry, cold front thru the region on Thursday. Strong 850 mb CAA will ramp up across the NC mountains during the day, resulting in gusty winds and falling temps. The piedmont will see temps near normal, while the mountains will be about 10 degrees below normal Thursday. The gusty winds will linger thru the overnight in the high terrain, but become fairly light in the piedmont. Temps will fall into the teens in the mountains and 20s piedmont. The combination of wind and temps will result in wind chills in the 0 to -10 F range toward daybreak Friday. Wind chill advisory is -5, and generally only elevations above 5000 ft look to get that cold. On Friday...a modified arctic air mass will build in from the NW. Winds will gradually subside in the mountains, but it will still feel brisk, with temps at least 10-15 degrees below normal, despite sunny skies. The center of the high settles over the central Appalachians by 12z Saturday. Lighter winds will keep wind chills above advisory criteria, but overall, it will be a chilly night. Lows in the teens to mid 20s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 130 AM EST Wednesday: The very cold airmass in place Saturday under surface high pressure centered over our region will move east and offshore from the mid Atlantic on Sunday. This will bring a change in wind to a more southerly direction resulting in a significant warming trend to around normal to start the week. The upper pattern will be nearly zonal from this weekend to mid week across our nation with an average slight trough east of the Rockies. The next shortwave will cross the Plains Sunday with some increased in moisture coming out of the Gulf across the SE. Expect some upslope showers ahead of this system to occur late Sunday and Sunday night from near Clayton GA to Tryon NC. The southerly 925mb wind of 15 to 30kts will shift to SW early Monday ending the upslope affect as it will be more parallel to the ridge lines. Both the GFS and ECMWF thins out or slightly dries out the approaching frontal precip band Sunday night into Monday. The GFS dries it out a bit more. Either way there will be scattered showers over the whole area but more initially over the NC mountains. There may be some very brief upslope precip along the TN and NC border north of AVL late Monday but that is mostly shown on the EC which may be the lower confidence model. The newest GFS dries our area out rapidly late Monday with no upslope in Mtns. High pressure builds in briefly on Tuesday then a mostly dry cold front is nearing from the NW late Tuesday night. Increase in clouds as a result. Temperatures of 10 to 15 degrees below normal Saturday will modify to near normal for Max Temps Monday and Tuesday. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: Update to KCLT TAF for the 09z AMD is to take TEMPO VLIFR and make that prevailing. Obviously confidence has increased and widespread VLIFR restrictions are in place across the Piedmont. Should improve by mid-morning. Otherwise, drier air will push into the area later today which should scour out any low clouds but then another wave of moisture associated with a strong but mainly dry front will lead to increasing clouds again toward the end of the period, and thus some MVFR has been introduced. Except at KAVL, winds generally lgt/vrb through the period with some variation in predominant direction depending on location of surface features. Outlook: Another front will approach late tonight and early Thursday with some light precip/restrictions possible. Dry and much colder through the weekend. Confidence Table... 09-15Z 15-21Z 21-03Z 03-06Z KCLT High 84% High 98% High 100% High 96% KGSP Med 65% High 95% Med 71% High 94% KAVL Med 61% High 100% High 85% High 100% KHKY Low 32% High 100% High 100% High 85% KGMU Low 57% High 95% Med 71% High 81% KAND Low 50% High 85% High 95% Med 75% 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: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...Dense Fog Advisory until 10 AM EST this morning for GAZ018-026- 028-029. NC...Dense Fog Advisory until 10 AM EST this morning for NCZ035>037- 056-057-068>072-082-502-504-506-508-510. SC...Dense Fog Advisory until 10 AM EST this morning for SCZ004>014- 019. && $$ SYNOPSIS...DEO NEAR TERM...TDP SHORT TERM...ARK LONG TERM...DEO AVIATION...TDP is the U.S. government's official web portal to all federal, state and local government web resources and services.