Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
107 FXUS64 KMRX 210552 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 152 AM EDT Thu Aug 21 2025 ...New DISCUSSION, AVIATION... .DISCUSSION... Issued at 137 AM EDT Thu Aug 21 2025 Key Messages: 1. Chances for showers and storms will be mainly focused further east today. More area-wide chances exist Friday through the weekend. 2. A pattern change is expected next week with cooler and drier conditions. Highs will be in the 70s for many locations with lows dropping well into the 50s. Discussion: Currently, an upper-level shortwave is just to our west as ridging recedes east with a weak front moving into the region. Hurricane Erin is off the Coastal Carolinas and expected to progress northeastward. With the approaching shortwave and broad northwesterly flow, the frontal boundary will move southeast during the day, becoming centered over western North Carolina. This will lead to slightly milder temperatures and reduced moisture and instability compared to yesterday. Rain chances will linger but will be focused further east closer to the boundary and better moisture. Instability will be more limited to below 1,000 J/kg but with decent DCAPE values remaining. Isolated flooding and strong wind gusts are possible, but the environment is less supportive than yesterday. On Friday, the upper-level shortwave will shift slightly east with the front weakening as it moves further south. Moisture and instability will still be less than yesterday but more supportive of area-wide rain chances. Heading into Saturday, a more pronounced shortwave will be noted over the northern U.S. with increasing frontogenesis in the Great Plains. This will keep a similar pattern in the region during the day before troughing deepens further with the front moving towards the region on Sunday, bringing continued chances for showers and storms both days. Sunday night into Monday morning, the front will move through the region with deep troughing persisting in the eastern U.S. through at least the first half of the week. Canadian high pressure will also gradually move into the area by mid-week. The extent of troughing and 850mb temperatures possibly dropping below 10 Celsius suggest this will be a significant cooldown for this time of year, especially compared to the pattern we`ve had. Many places will see highs about 10 degrees below normal. Overnight lows could drop well into the 50s for many as strong radiational cooling will be likely by Tuesday and Wednesday. && .AVIATION... (06Z TAFS) Issued at 137 AM EDT Thu Aug 21 2025 Deteriorating aviation conditions due to fog and low ceilings are expected over the next few hours with MVFR or lower expected at all of the terminals with MVFR already being reported at TYS and TRI. Fog should lift soon after sunrise with MVFR ceilings possibly continuing through much of the morning. Otherwise, light northerly winds and SCT clouds around 5,000 feet. A few showers and storms are possible but are likely to stay east of the terminals. However TRI has the highest chance of seeing some. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 89 70 88 70 / 10 10 60 20 Knoxville McGhee Tyson Airport, TN 87 70 88 70 / 20 10 40 30 Oak Ridge, TN 87 69 89 69 / 10 10 40 20 Tri Cities Airport, TN 84 66 85 66 / 40 20 30 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...BW AVIATION...BW