Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
880 FXUS64 KMRX 132309 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 709 PM EDT Wed Aug 13 2025 ...New AVIATION... .DISCUSSION... Issued at 133 PM EDT Wed Aug 13 2025 Key Messages: 1. Decreasing rain chances and flooding threat through the rest of the afternoon and evening. 2. Scattered showers expected with an upper trough passage tomorrow, mainly in the afternoon. 3. Reduced coverage of diurnal shower/thunderstorm chances through the weekend. Above normal temperatures and muggy conditions return over the weekend and continue for the first half of next week. Discussion: A low pressure system over AL has been pumping Gulf moisture into our area today, producing high precipitable water content and efficient rainfall rates that have led to flooding. Radar trends show decreasing overage and intensity over the last few hours, but southern sections will maintain a threat of flooding through the rest of the day. The low will progress eastward tonight across GA and SC, shifting the 850-500 mb flow to a more westerly direction tonight. With the reduction of deep moisture and lack of forcing, most of the overnight hours should be dry. However, abundant low level moisture in place will likely result in fog and low clouds area wide overnight and into tomorrow morning. Fog could be dense in some locations. A shortave trough is located from the eastern Great Lakes to the Ozarks today, and will be moving across our area tomorrow. We will still have a good amount of moisture through the column, but PW values drop into the 1.75-1.9 inch range, and MLCAPE stays under 1000 J/kg for most of the area. Forcing with the trough should initiate convection in the late morning and early afternoon, with the terrain areas being favored for the best coverage. The flooding threat will be less tomorrow given the slightly drying column and stronger steering winds aloft, but some localized flooding may be possible in areas that had a lot of rain today. A ridge over the Southwest will merge with the ridge over FL, leading to a large, amplified ridge over the TN/OH Valley regions over the weekend. This will provide mostly dry conditions for our area, aside from a few isolated/scattered diurnal showers and storms in the higher terrain areas. Temperatures will be rising above normal, with highs in the lower and mid 90s by Sunday. This will continue through the first half of next week as the ridge remains nearly stationary over the region. && .AVIATION... (00Z TAFS) Issued at 706 PM EDT Wed Aug 13 2025 VFR conditions will continue for much of the evening with deteriorating conditions late tonight into the morning hours. IFR is expected at all of the sites with periods of LIFR possible, primarily due to fog. Light showers are possible around the terminals, but most places are likely to stay dry for the night. Gradual improvements to VFR are expected late in the morning heading into the afternoon. Additional showers and storms are possible again during the afternoon hours but with more limited coverage. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 88 72 91 / 40 50 30 30 Knoxville McGhee Tyson Airport, TN 71 87 70 91 / 40 50 20 20 Oak Ridge, TN 70 87 70 90 / 30 50 20 20 Tri Cities Airport, TN 68 83 67 87 / 40 50 20 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...DGS AVIATION...BW