


Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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-- Discussion containing changed information from previous version are highlighted. --804 FXUS64 KMRX 110606 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 206 AM EDT Fri Jul 11 2025 ...New SHORT TERM, LONG TERM... .SHORT TERM...-- Changed Discussion --(Today and tonight) Issued at 202 AM EDT Fri Jul 11 2025 Key Messages: 1. Patchy to areas of fog developing overnight into early Friday morning. River Valleys will favor the most likely chances for localized dense fog. 2. Mostly dry afternoon but some isolated afternoon shower and storms will favor higher elevation locations. Discussion: Regional radar only shows a few isolated, small and shallow showers in higher terrain as a mostly dry overnight is expected. Main focus will be on the potential for some dense fog. Utilizing nighttime microphysics and night fog GOES-16 products, some fog is distinguishable within northern rivers valleys. Comparing low ceiling and fog probabilities from the HREF ensemble, hi-resolution models hint that localized dense fog will be more limited to river valleys with more of a low ceiling developing throughout the morning hours. Will monitor trends into the morning and issue any products for fog as needed. Upper ridge will replace a departing shortwave trough this afternoon. Weak height rises of roughly 2dam will promote a slight warming trend. The warm and humid summer airmass will allow for additional diurnal convection. However, a notable subsidence inversion around 650mb suggest the associated high pressure will help limit afternoon storm coverage. Generally expect isolated to weakly scattered showers and storms favoring higher terrain of the Appalachian Mountains and Cumberland Plateau. Brief gusty winds and heavy downpours are possible with the strongest storms. Mostly dry for valley locations.-- End Changed Discussion --&& .LONG TERM...-- Changed Discussion --(Saturday through Thursday) Issued at 202 AM EDT Fri Jul 11 2025 Key Messages: 1. Diurnal summertime convection continues through the forecast period with some day-to-day variations in expected coverage. Troughs passing to our north late weekend and again late next week are expected to influence the most scattered convection. 2. Hot conditions return as an upper ridge builds back into the region for the middle part of the work week, with heat indices in the mid 90s to near 100F becoming more common across valley locations. Discussion: As we head into the weekend the synoptic pattern in the upper levels will consist of ridging across the western & eastern CONUS while a shortwave trough sags through central Canada into the northern Plains. Hot and humid conditions with heat indices in the 90s will be widespread with additional diurnal convection Saturday. Though, to varying extent, CAMs are depicting semi-organized tstorm clusters with a weak southern stream impulse briefly enhancing effective bulk shear near 15-20kts. MLCAPE will generally range from 1000-2000 J/kg per 00Z HRRR soundings. A low-end strong to isolated severe threat cannot be totally ruled out but timing of the potential impulse will play a crucial role on whether or not that low-end threat plays out. Sunday into Monday the aforementioned shortwave trough will swing through the Great Lakes and Ohio Valley with an associated surface boundary slowly advecting towards the region. Diurnal showers and storms are generally expected each day but the exact coverage is uncertain due to uncertainty in the timing and positioning of the shortwave & boundary. Overall, any potential severe threat seems rather low but we will continue to monitor hi-resolution models as they come into temporal scale. Upper ridging builds back into the region mid-week. Daily chances of showers and storms continue but subsidence aloft should help inhibit coverage. Main weather message will be to focus on the return of hot conditions with heat indices potentially climbing back into the mid 90s to near 100F Tuesday and Wednesday. Long range guidance suggest a deeper trough swings back through late week with increasing coverage of showers and storms.-- End Changed Discussion --&& .AVIATION... (06Z TAFS) Issued at 100 AM EDT Fri Jul 11 2025 Fog and/or low cloud development is very likely early in the period especially TYS and TRI. Will take both as low as IFR, but could see lower conditions. At CHA will include a tempo MVFR group for now late tonight. Will see scattered showers and thunderstorms around again mainly this afternoon, and will include prob30 thunder groups all sites around the time of highest probability. && .PRELIMINARY POINT TEMPS/POPS...-- Changed Discussion --Chattanooga Airport, TN 91 71 92 73 / 30 10 40 10 Knoxville McGhee Tyson Airport, TN 90 71 91 72 / 20 10 30 20 Oak Ridge, TN 90 70 91 71 / 20 10 40 20 Tri Cities Airport, TN 87 68 88 68 / 30 10 30 40-- End Changed Discussion --&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...KRS LONG TERM....KRS AVIATION...