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

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000 FXUS64 KMRX 201900 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 300 PM EDT Sun May 20 2018 .SHORT TERM...
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(Tonight and Monday)...Upper heights continue to rise across the southern Appalachians this afternoon atop weak high pressure at the surface allowing for ample heating. With that, convective initiation has occurred across the higher terrain of both the mtns/Plateau. Further heating this afternoon is expected to favor additional coverage in the southern TN valley as convective temps are reached/exceeded. Guidance still seems to suggest that any weak capping will hold for valley locations north of I40. Thus, the fcst features high end chance to low likely pops close to the GA/AL/TN lines, tapering to slight chances along I40, then down to non mentionable levels closer to KY. As for threats today, any convection that does occur could reach to heights supportive of small hail. Likewise, given relatively weak motion vectors, think storms could also present a concern for brief heavy rainfall and isolated flash flooding, although not likely. Otherwise, coverage will diminish with heating loss tonight leading into a partly cloudy evening. Ample moisture in the decoupled BL could lead to another night of patchy fog, the most dense of which is favored in the valleys of extreme northeast TN and southwest VA, as well an any locales receiving good rainfall today. Much the same on Monday as mainly diurnal heating induced convection is favored while a weak upper disturbance amidst the broader H5 flow rotates atop the FL gulf coast. With that, pops will be a bit higher as deeper moisture advects northward, therefore the fcst will feature regionwide likely pops on Monday. Temperatures on Monday with remain slightly above normal levels .LONG TERM...(Monday night through Sunday)...The Northeastern U.S. upper trough amplifies early in the period helping to push a frontal boundary south through the forecast area. There will be a higher chance of showers and thunderstorms across the forecast area on Tuesday ahead of the front. However, probability will be dropping across much of the area through the end of the work week as drier and slightly more stable air filters into the region. Moisture and instability will be gradually increasing over the weekend ahead of another Midwest upper trough. A few more showers and thunderstorms will be possible across the area in this environment, so raised pops into a higher chance category over the weekend. High temperatures will be generally in the lower and middle 80s through Wednesday, and then may inch up a bit into the middle and upper 80s in the slightly drier airmass behind the boundary. Lows will be mainly in the lower and middle 60s, although may be a little warmer as moisture returns later in the week.
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Chattanooga Airport, TN 69 82 66 82 / 40 60 30 50 Knoxville McGhee Tyson Airport, TN 68 82 64 82 / 20 60 30 50 Oak Ridge, TN 67 84 65 83 / 20 60 30 50 Tri Cities Airport, TN 63 82 61 80 / 10 60 30 50
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ CDG/TH is the U.S. government's official web portal to all federal, state and local government web resources and services.