Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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031 FXUS64 KMRX 270538 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 138 AM EDT Thu Jun 27 2024 ...New AVIATION... .UPDATE... Issued at 951 PM EDT Wed Jun 26 2024 The main change for the evening update will be to adjust PoP/Wx grids to match current radar trends. Overall, the forecast is in good shape, but PoPs will be raised where precip is ongoing and is expected to move in th enext few hours. We should see a decreasing trend to shower coverage and intensity, with no severe storms expected. A few isolated wind gusts up to 40 mph may be possible with outflow boundaries. The loss of heating and the lack of shear will favor weakening convection. A few tweaks to hourly temp/dewpoints will be made as well, but no major changes are needed. Tomorrow`s rain chances will be focused mainly in the southern half of the area, closer to the surface front/trough that will be moving through tonight. && .SHORT TERM... (This evening through Thursday) Issued at 313 PM EDT Wed Jun 26 2024 Key Messages: 1. Isolated showers and thunderstorms expected through Thursday. A few strong storms are possible this afternoon and evening, with wind damage being the main threat. 2. Slightly cooler tomorrow, but still near normal temperatures. Discussion: A weak upper level trough and associated cold front will swing down from the northwest and into our area this evening. Latest HRRR runs show isolated to scattered showers and storms developing between 4 PM and 5 PM across the Cumberland Plateau, east TN mountains and southwest VA mountains. Some of the showers and storms across the plateau will likely drift down into valley locations this evening. With marginal instability and very weak shear in place, a few strong storms are possible. With dry air in place from the surface to the midlevels, the main threat will be damaging winds. As we go further into the evening/overnight hours, additional showers and storms will move in from the west. This is as forcing becomes more favorable with the arrival of the trough. However, chances for strong storms become less favorable during this time as instability will be lower compared to pre-sunset hours. Most areas will see little to no precip. However, any location that receives a thunderstorm could see a quick 0.25 inches to 0.5 inches. We will likely see a lull in the precip early tomorrow morning. Then, as we begin to destabilize with daytime heating, see an uptick in shower and storm development Thursday afternoon. The best chance of seeing any precip will generally be from I-40 and southward, which is closer to where the better forcing will be. && .LONG TERM... (Thursday night through next Wednesday) Issued at 313 PM EDT Wed Jun 26 2024 Key Messages: 1. Diurnal showers and thunderstorms through the weekend with highest chances of showers and thunderstorms on Sunday. 2. Drier next week with ridge building across the region. Signals for hot weather returning. Discussion: Shortwave trough on Thursday will flatten the ridge across the Tennessee Valley and Southern Appalachians for Friday and into the weekend. A stronger shortwave trough will move eastward across the Great Lakes over the weekend with a cold front moving southeastward towards our region on Sunday. Ahead of this front, diurnal convection will be possible on Friday and Saturday, mainly across the higher elevations. By Sunday, more widespread showers and thunderstorms are expected ahead of this cold front. Model guidance indicates MLCAPE values on Sunday afternoon expected to be in the 1500 to 2000 J/Kg range with weak bulk shear of 15 to 20 kt. This will favor the possibility of some stronger storms, including strong wind gusts, but the overall severe weather risk isolated and low. The primary risks this weekend (mainly Sunday) will be related to damaging winds and the potential of flash flooding due to heavy rainfall rates as PW values rise into the 2.0 to 2.2 inch range ahead of the front. Behind this front, somewhat cooler and drier air is expected early next week. However, ridging builds back in mid-week with a warming temperature trend on Tuesday and Wednesday resulting in above normal temperatures once again. && .AVIATION... (06Z TAFS) Issued at 121 AM EDT Thu Jun 27 2024 An upper trough with a short-wave is evident on radar and satellite over east Tennessee. This wave is producing widespread showers and a few thunderstorms this morning. Will continue with tempo showers at all TAF sites through much of the early morning hours. Moistening of the boundary layer is allowing MVFR to almost IFR ceiling to develop and expect to continue through around mid- morning. A shear axis will remain over east Tennessee early this afternoon before moving east. This wave along with HREF CAPES of 1000+ at CHA and TYS to produce scattered showers and thunderstorms this afternoon. Gradual clearing expected this evening. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 89 73 93 75 / 50 20 30 10 Knoxville McGhee Tyson Airport, TN 89 71 93 73 / 40 10 30 20 Oak Ridge, TN 88 70 92 73 / 40 10 30 10 Tri Cities Airport, TN 87 67 91 70 / 40 0 40 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...DGS LONG TERM....JB AVIATION...DH