Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
870 FXUS64 KMRX 201116 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 716 AM EDT Wed Aug 20 2025 ...New AVIATION... .DISCUSSION... Issued at 149 AM EDT Wed Aug 20 2025 Key Messages: 1. Scattered to numerous storms are likely this afternoon and evening. Locally strong wind gusts and isolated flooding are possible. 2. Chances for showers and storms continue Thursday and Friday with decreased coverage. 3. A pattern change is expected next week with cooler and drier conditions. Discussion: Currently, broad ridging is centered near the Rockies with Hurricane Erin east of Florida and progressing towards the Coastal Carolinas. A weak frontal boundary is also near the Ohio River Valley. Throughout the day, ridging will slowly regress westward with a weak shortwave passing to our north. Nevertheless, hot and humid conditions can still be expected with increased moisture in comparison to yesterday. These features will support diurnal storms but and more area-wide coverage with addition of moisture. MLCAPE will likely exceed 1,500 J/kg for many areas with DCAPE values approaching 1,000 J/kg. This will make the case for locally strong wind gusts and a few stronger storms. Also, localized flooding will remain possible for places that see repeated rain. Thursday and Friday, Hurricane Erin will move off the Coastal Carolinas and then progress northeast back into the Atlantic. Generally weak northerly to northwesterly flow will remain in place locally with the frontal boundary staying near the region and upper- level shortwaves. This will keep chances for showers and storms in the forecast, but lessened moisture is indicated compared to today with PWATs possibly nearing 1 inch in some locations. Instability will still support some convection but with less coverage likely. The general northwesterly flow pattern will continue through the weekend with moisture still sufficient for lingering rain chances. By Sunday, broad and deepening troughing will be noted to our northwest, along with strengthening frontogenesis. By Monday, the trough and frontal boundary are expected to move through the region, leading to notably cooler temperatures heading into the upcoming week. 850mb temperatures could drop close to 10 Celsius, which is below the 10th percentile for this time of year. Expanding high pressure will also promote stronger subsidence and greater chances for overnight temperatures to drop into the 50s for many places. && .AVIATION... (12Z TAFS) Issued at 707 AM EDT Wed Aug 20 2025 Patchy fog and especially the MVFR clouds this morning will linger a little longer before eventually mixing out. This afternoon into evening scattered showers and TS are expected, bringing brief reductions in VIS at times. Only a 10% chance of MVFR CIGs during afternoon convection. Low clouds may develop late in the period at KTRI. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 93 71 90 70 / 60 20 20 0 Knoxville McGhee Tyson Airport, TN 90 71 88 69 / 60 20 20 10 Oak Ridge, TN 89 70 87 68 / 70 20 10 0 Tri Cities Airport, TN 87 68 84 66 / 70 30 30 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...BW AVIATION...Wellington