Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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777 FXUS64 KMRX 262314 AAA AFDMRX Area Forecast Discussion...UPDATED National Weather Service Morristown TN 714 PM EDT Wed Jun 26 2024 ...New AVIATION... .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... (00Z TAFS) Issued at 711 PM EDT Wed Jun 26 2024 Showers and a few thunderstorms are expected to move into the TN Valley this evening, with the highest chances at TRI and TYS, where TEMPOs will be included for MVFR conditions at TS, and a lower chance at CHA. The front will move through around midnight, shifting winds to NW. An MVFR ceiling is expected to develop behind the front late in the night and tomorrow morning, lifting in the late morning. Additional showers may develop tomorrow afternoon in the southern half of the area, with scattered coverage at best leading to PROB30s in the TAFs. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 99 73 89 73 / 20 40 50 10 Knoxville McGhee Tyson Airport, TN 96 71 89 71 / 20 50 40 10 Oak Ridge, TN 96 70 88 70 / 20 60 30 0 Tri Cities Airport, TN 94 68 87 67 / 30 50 50 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... LONG TERM....JB AVIATION...DGS