Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 150816 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 316 AM EST Mon Jan 15 2018 .SHORT TERM...(Today and Tonight)...Some weak isentropic lift over the area to start, with mainly high/mid clouds. Light returns on radar, and some flurries may reach the surface in spots so will add these for the morning mainly northern two thirds of the area. Will see quite a bit of sunshine once the area of weak lift pulls out, and temps will be a bit warmer. Tonight will see moisture increasing again ahead of the next system, and some light snow may reach the plateau by late in the night. Will carry some slight chance to chance PoPs in these areas late. Main tweaks to MAV max and min temps will be to lower them a bit most locations. .LONG TERM...(Tuesday through Sunday)...The long term period starts out with snow and another arctic front crossing the area, followed by another shot of bitter cold through midweek. A warmup will follow as we head towards the weekend. For Tuesday, a positively tilted trough will be just to our northwest with the associated surface cold front pushing through the forecast area. Temperatures will be cold enough for an all snow event and there`s plenty of lift -- the big question continues to be the amount of moisture available to work with. Models are in good agreement on the onset of snow -- daybreak across the northern plateau, midday across the TN valley, and midafternoon across the eastern mountains. However, there`s still some disagreement with how fast the boundary exits the area (and therefore how much snow will fall), with the ECMWF and NAM continuing to be slower with the progression of the trough and front than the GFS. WPC bumped QPF up a bit again with this update, buying into the slightly slower frontal progression. Opted to lean towards this thinking as well, and as a result bumped snow totals up a bit more with this update. Still thinking it 1-2" event for most of the area, with slightly higher amounts along the northern plateau and SW VA and slightly lower amounts in the southern TN valley, but this will probably be enough to cause some travel issues during the day. Snow will gradually taper off Tuesday evening with some lingering showers possible overnight east of I-40. The trough lifts northeast on Wednesday, bringing clearing skies and the coldest day of the week with highs in the low to mid 20s. With the colder air overhead, both Tuesday night and Wednesday night will be bitterly cold with lows in single digits to lower teens. While wind speeds won`t be very high, we will see wind chills drop below zero in the higher elevations and around 5 degrees elsewhere. Upper level troughing finally kicks out of the area completely for Thursday, and ridging will build across the area. This will help temperatures rebound as we head into the weekend, with highs in the 30s for Thursday, 40s for Friday, and 50s for the weekend. The next chance for precipitation (this time rain with temperatures well above freezing) arrives later Sunday as another cold front approaches the area. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 46 27 32 13 / 10 10 50 40 Knoxville McGhee Tyson Airport, TN 42 26 31 12 / 10 10 70 50 Oak Ridge, TN 43 27 28 12 / 10 10 70 40 Tri Cities Airport, TN 40 23 35 13 / 10 10 60 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ LW/EMH is the U.S. government's official web portal to all federal, state and local government web resources and services.