Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 301143 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 643 AM EST Mon Nov 30 2020 .SYNOPSIS... A strong low pressure system will cross the area this morning. In the storm`s wake, Snow is expected to develop in the mountains near the North Carolina and Tennessee border through Tuesday. Another strong low may cross the region at the end of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 640 AM: Line of convection with gusty winds and possibly a rumble of thunder associated with an advancing cold front will move east of the area by 9 AM. A few light showers may linger across the area early this morning before clearing develops outside of the mountains. Some clouds will break containment and spread across the foothills and piedmont, especially downstream of any convergence zones created by gaps in the escarpment. Some guidance even suggests and isolated rain or snow shower could develop in these zones. Will leave any mention out for now. Westerly winds pick up behind the front and become gusty across the area which continue at least through the evening and maybe even overnight. Should be an early high near or above normal with temps falling through the afternoon. Lows will be below normal. For the mountains, the initial showers will end with the morning passage of the cold front. Temps will fall much earlier, especially across the higher elevations of the Smokies, then across all the higher elevations. Valleys will remain relatively warm with nearly steady or slowly falling temps until afternoon. Deep NW flow moisture and good upslope flow, along with some weak instability and upper divergence, will lead to a NW flow snow event for the TN border counties. Expect snow to begin in the Smokies this morning with snow moving up the spine of the Appalachians through the day. Snow levels will drop to the valleys by afternoon. Given the amount of moisture and forcing, will convert the watch to a high elevation warning and low elevation advisory. Snowfall totals of 4 to 6 inches will be common across the warning area with up to 8 inches near Sam`s Gap, over the Smokies, and even the high elevations of Graham County. The lower elevations will average 2 inches but could see isolated higher amounts. Will keep Buncombe out of any winter products for now as most of the populated areas will see less than an inch; however, the higher elevations along the parkway near the Black Mountains will see accumulations. Very gusty winds develop over the higher elevations with some higher elevation locations seeing wind chill values around 0. Lows in the valleys will generally bottom out around 20 degrees or higher. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 200 AM Monday: Snow will be the topic of discussion to start out the short term. NW-ly moisture advection gradually weaves out starting at daybreak Tuesday along the NC-TN border and the spine of the Blue Ridge. This will put an end to the snow in the mountains by sunset at the very latest, but even just some shallow low-level moisture will keep light snow going in the favorable NW upslope locations along the northern tier through the afternoon. Expect snow totals to be 4-6+" above 3500 ft with a substantial drop off at any elevation level below that. After the snow tapers off, the real weather story will be the deep cold air that filters in across the entire cwa. With steady caa and low thicknesses, expect temperatures to take a huge dip Tuesday and Tuesday. Readings will be in the order of 10+ degrees below normal for this time of the year. 20s and 30s for highs in the higher terrain and 40s elsewhere, while min temps drop into the 10s and low 20s in the mountains with mid and uppers 20s east of the mountains. By the middle part of the week, the cwa should begin to moderate as the upper low ejects to the northeast and shortwave ridging builds in from the west. Sfc high will control the overall weather pattern and keeps the area dry through the rest of the period. Another upper low will be knocking on our doorsteps with increasing clouds and waa by 12Z Thursday, but should stray away from impacting the short-term period with any precip at this time. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 AM Monday: Sfc high continues to influence the beginning portions of the medium range. Conditions begin to deteriorate late Thursday into Friday as an upper low swings in from the mid MS Valley. The GFS continues to be more progressive than the ECMWF, but they are in agreement with the overall set up. PoPs are in the forecast due to the upper low and attendant frontal boundary during the last day of the work week. The ECMWF run would suggest keeping PoPs going into the first half of the day on Saturday. Where the global models begin to diverge is timing and what happens over the weekend. The GFS carries a secondary upper low across the southern and central Plains and pushes into the area on Sunday, but low-level support for any precip will be minimal. The weekend looks mostly dry with the exception of day 7 when the upper low is projected to be ejected offshore by an upper trough that digs into the eastern CONUS. This setup could be favorable for another rain/snow event for the mountains, but is way too far out for a confident solution. Temperatures will remain slightly below-normal for the duration of the extended. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Line of convection will move east of KCLT and KHKY before 14Z. Until then, expect IFR cigs and TEMPO IFR vsby in variably gusty winds. LLWS will is also expected at KCLT as the strong low level jet passes by. Elsewhere improving vsby and cigs with only a passing light shower this morning. Winds become WSW and gusty through the morning and continue through into the evening then diminishing after midnight. KAVL will see NNW wind becoming gusty and continuing through the night. Low level VFR clouds will spread back across the foothills and piedmont during the afternoon into the evening before clearing again. Low clouds and a very light snow shower may move up the valley to KAVL tonight, but chance too low for the TAF for now. Outlook: Windy conditions linger into Tuesday, with low cigs and snow showers possible in the mountains as well. Otherwise, VFR conditions expected. Confidence Table... 11-17Z 17-23Z 23-05Z 05-06Z KCLT High 83% High 100% High 100% High 100% KGSP High 89% High 100% High 100% High 100% KAVL High 100% High 85% High 100% High 100% KHKY Med 78% High 100% High 100% High 100% KGMU High 94% 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 scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Winter Weather Advisory below 3500 feet until noon EST Tuesday for NCZ033-048>052-058. Winter Storm Warning above 3500 feet until noon EST Tuesday for NCZ033-048>052-058. SC...None. && $$ SYNOPSIS...RWH NEAR TERM...RWH SHORT TERM...CAC LONG TERM...CAC AVIATION...RWH

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