Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
989 FXUS64 KMRX 130012 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 812 PM EDT Sat Jul 12 2025 ...New AVIATION... .SHORT TERM... (This evening through Sunday morning) Issued at 141 PM EDT Sat Jul 12 2025 Key Messages: 1. Scattered showers and storms will continue this afternoon and evening. A few may become strong to severe. Primary concerns with any strong to severe storm will be damaging winds between 40-60 mph and isolated flooding. Discussion: Upper trough across the Midwest and Great Lakes will provide enhanced forcing which will support scattered showers and storms through this evening. Bulk effective shear still in the 15 to 20kt range per model soundings and RAP analysis. Rap analysis on the SPC meso page shows MLCAPE values around 2,500 J/kg through the afternoon. This mix of instability and minor shear will allow storms to be loosely organized, compared to typical summer-time pulse. Basically, this just means that there is a better chance for a few isolated strong to severe storms today compared to yesterday. The main hazards will any strong storm will be wind gusts up to 60 mph. The risk for isolated flooding also remains due to the high PW airmass. Coverage of showers and storms will decrease by sunset but a few isolated showers and storms may linger through the night due to some slight enhancement in the 500 mb vorticity. Also, patchy dense fog is possible tonight across any location that receives rainfall today. && .LONG TERM... (Sunday through next Saturday) Issued at 141 PM EDT Sat Jul 12 2025 Key Messages: 1. No change from previous forecast. Daily summer-time convection continues through the long term. Still potential for increased coverage by late week as a trough returns to the eastern U.S. 2. Hot conditions return as an upper ridges strength peaks in the middle part of the work week. Heat indices in the mid 90s to near 100F will become more common across valley locations. Discussion: No real change to the long term. Upper trough will continue to slowly pivot eastward Sunday through Monday with continued chances for diurnal convection. Under weak flow, we will have limited chances to see any severe storms. The best coverage each day will continue to be focused along our high terrain areas. Expect heat indices in the mid 90s to near 100F to become more widespread across the southern and central valley by Monday, with values in the low to mid 90s across northeast TN and southwest VA. The hottest days look to be Monday through Wednesday. Slightly lower temps, back in the upper 80s to low 90s expected thereafter. Additionally, we are still keeping an eye on a late week trough that has potential to bring increased coverage of afternoon shower and storm activity across the area. && .AVIATION... (00Z TAFS) Issued at 748 PM EDT Sat Jul 12 2025 Convection previously impacting TAF sites is beginning to diminish and depart east. An additional line of convection is moving through western and central KY but the activity is anticipated to wane before making it to any TAF sites. HREF probabilities suggest KTRI has the highest chance of fog/low cig, and they did observe moderate convection this afternoon. Opted to include brief MVFR conditions because of this. Additional showers and storms expected tomorrow afternoon but believe the coverage will be more isolated in nature. Only included vicinity mention at CHA where CAMs are in better agreement. It is possible mentions may need to be included at other sites in future issuances. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 72 94 73 95 / 10 40 0 30 Knoxville McGhee Tyson Airport, TN 72 91 72 94 / 10 30 10 30 Oak Ridge, TN 70 91 71 93 / 20 40 10 40 Tri Cities Airport, TN 68 87 68 89 / 30 50 20 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION...KRS