Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
615 FXUS64 KMRX 190549 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 149 AM EDT Tue Aug 19 2025 ...New DISCUSSION, AVIATION... .DISCUSSION... Issued at 143 AM EDT Tue Aug 19 2025 Key Messages: 1. Limited coverage of showers and storms is expected today, mainly across the mountains of East Tennessee and southwest North Carolina. Localized flooding is possible due to heavy rainfall. 2. Increased coverage of storms is expected Wednesday through Friday with locally strong wind gusts and isolated flooding possible. 3. Some rain chances linger into the weekend, but notably cooler temperatures are expected by early next week. Discussion: Currently early this morning, broad ridging is in place across the eastern two-thirds of the U.S. with 500mb heights reaching 5,980m just east of the Rockies. A weak, quasi-stationary frontal boundary also remains centered to our northeast. Patchy morning fog is likely again, especially in places that see better clearing as dew points remain fairly high. This morning fog will give way to another day of hot and humid conditions under the influence of widespread ridging. Overall coverage of storms will be limited but in the presence of over 1,000 J/kg MLCAPE, especially further south where moisture will be more prevalent. Efficient mixing will allow for DCAPE values to reach at or above 1,000 J/kg, supporting locally strong wind gusts with any storms. However, coverage will be primarily over the mountains of Tennessee and North Carolina. Localized flooding due to heavy rainfall will be possible. For most, the main focus will be the heat with heat index values likely to reach around 100 degrees across the southern and central Valley. By Wednesday, Hurricane Erin will come into closer view and is forecast to be approaching the Carolina coast. Increasing troughing over the northeast will push ridging further to the west. The frontal boundary to our north will progress closer to the area, which combined with height falls and increased moisture, will increase convective coverage. This general pattern will continue through Friday with coverage of convection shifting further south as the front progresses into the region. During this time, similar thermodynamic profiles can be expected, but DCAPE values may be lessened as heating becomes more limited. Repeated storms could lead to locally heavy rainfall totals and isolated flooding. But this threat will heavily depend on how much coverage is seen as most places have been dry for days. Heading through the weekend and into early next week, the pattern will shift even more significantly as troughing dives from Canada and spreads over the eastern U.S. 850mb temperatures look to reach around 12 Celsius, which is on par with normals for late September into early October. This further emphasizes the likelihood of below normal temperatures. && .AVIATION... (06Z TAFS) Issued at 143 AM EDT Tue Aug 19 2025 The main aviation impact will be the development of patchy fog around TRI, which was left at MVFR for the time being. Conditions above or below this category are certainly possible. At the other sites, fog potential is a lot more limited. Otherwise, very light winds and SCT/FEW clouds around 5,000 feet are expected. Isolated storms are expected across the mountains of Tennessee and North Carolina but with no impact expected at the terminals. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 94 72 93 72 / 20 10 50 10 Knoxville McGhee Tyson Airport, TN 93 72 91 71 / 20 10 40 20 Oak Ridge, TN 93 72 90 70 / 10 10 50 20 Tri Cities Airport, TN 89 67 88 68 / 10 0 50 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...BW AVIATION...BW