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

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000 FXUS64 KMRX 241917 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 317 PM EDT Wed May 24 2017 .SHORT TERM /Tonight and Thursday/... First wave of storms has cleared the area into Virginia and North Carolina, leaving a fairly stable environment in it`s wake. Some clearing has occurred across the area, which may help to create some additional instablity between the 20-23z time period ahead of the surface cold front currently moving into the Cumberland Plateau. With progged CAPE values of 500-1200 J/kg, and some increased lift/shear from a northward surging LLJ, a strong to locally severe thunderstorm is possible within the tornado watch area. This watch is in effect mainly for the isoalted potential for a brief, weak tornado that could occur along/near the boundary along the Plateau. Latest runs of the HRRR/NAM show most of this activity remaining below severe limits, with the best threat to the northeast in KY. Still, given the good shear profile and some limited CAPE, a severe threat with an isolated tornado risk will exist for most of the area until sunset. The asociated thunderstorm and shower activity with the front will wane overnight as it pushes east, through cloud cover and some locally patchy fog will exist late tonight into Thursday morning. As the base of the trough swings through the area on Thursday, an additional shortwave trough will rotate down from KY, bringing an another round of showers for most of the area on Thursday. Also, most of the region will stay overnight (safe for the far southern zones) under a cool NW flow. Highs on Thursday will be lucky to hit 70 degrees across the northern half of the area due to this cloud cover -- while some clearing late near Chattanooga will help warm things up a bit more. .LONG TERM /Thursday Night through Wednesday/... Had to keep a few pops around across the northeastern corner of the viewing area on Thursday night as the deep upper low edges very slowly east toward the northeastern states. There will finally be a twenty four hour period of pops less than 10 percent on Friday as drier air builds in behind the departing trough with a brief period of ridging. Had to bring the pops back over the weekend as a the ridge gets knocked down by a few waves of weak short wave energy. The first builds across the Mid South on Saturday with a gradually strengthening southerly component to the flow with increasingly warmer and more humid air on the return. By Sunday, the probability of precip remains in the likely category as a deepening long wave trough builds into the Great Lakes and Mississippi Valley. Showers and thunderstorms will form ahead of an associated cold front Sunday into Sunday night. Pops were broadbrushed back through the medium chance range on Monday as the upper flow becomes generally parallel to the surface front. Had to continue with low to slight chance pops for some convection Tuesday into Wednesday as more Great Lakes/Upper Midwest troughing is indicated in the medium range models. It appears another surface cold front could build southeast into the Southern Appalachians Tuesday night into Wednesday in this flow regime. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 54 74 54 85 / 50 20 0 10 Knoxville McGhee Tyson Airport, TN 54 69 54 81 / 50 50 10 10 Oak Ridge, TN 54 71 54 82 / 50 50 10 10 Tri Cities Airport, TN 53 63 52 77 / 60 80 30 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ AMP/TH

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