Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
518 FXUS64 KMRX 011026 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 626 AM EDT Tue Jul 1 2025 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 1227 AM EDT Tue Jul 1 2025 Key Messages: 1. Showers and thunderstorms expected ahead of a cold front today. Most areas should receive rain this evening with more widespread coverage. 2. Heavy rain rates are expected which will result in isolated flash flooding. Discussion: A shortwave trough will amplify the longwave pattern across the Tennessee and Ohio Valleys. With height falls and an associated surface front, more widespread convection is expected this afternoon and evening. At this time, the most probable frontal passage is around 21z to 03z which will be when the highest chances of thunderstorms is expected area-wide. RAP forecast PW values ahead of the front will be in the 2.0 to 2.2 inch range across the area which will be favorable to heavy rain rates of 3 to 4 inches per hour. This can quickly lead to flash flooding issues, especially for urban areas with large amounts of impervious surfaces. There will be enough instability for some stronger updrafts as MLCAPE approaches 2000 to 2500 J/Kg between Knoxville and Chattanooga this afternoon. However, the RAP shows forecast soundings remaining saturated with heights which will limit thermodynamic damaging wind potential and increase tropical rain rates. Because of this, the overall severe weather risk is low, but some isolated gusty winds are possible with the strongest storms. Behind the front, drier air begins to arrive tonight into Wednesday morning. With the front across our southern areas, some overnight convection may continue to linger across far southeast Tennessee and southwest North Carolina. && .LONG TERM... (Wednesday through Tuesday) Issued at 1227 AM EDT Tue Jul 1 2025 Key Messages: 1. Low chances of thunderstorms Wednesday across far southeast Tennessee and southwest North Carolina. 2. Dry weather through Independence Day and into the weekend. 3. Moisture begins to increase this weekend with a return of hot, humid conditions and isolated thunderstorms, mainly across the mountains. Heat index values will be in the 100-105F range this weekend near Chattanooga. Discussion: The front will begin to become stationary to our south and may result in some isolated to scattered convection in the vicinity of our far southeastern counties of southeast Tennessee and southwest North Carolina on Wednesday. However, most areas remain dry. With subsidence and northwest flow aloft, Thursday and Friday are forecast to remain dry with mostly clear and warm conditions. The only impacts will be the heat beginning to return on Friday as ridging begins to build in from the west. Those outdoors will need to practice heat safety and remain hydrated on this hot, sunny Independence Day. This weekend, the ridge axis begins to shift over our region with hot, humid conditions. Isolated convection will be possible across the mountains and the highest peaks of the plateau, but most areas remain dry. There`s considerable spread in potential weather early next week with the potential for a shortwave across the Great Lakes or a tropical low pressure system to our south. At this time, there`s no likely impacts for our area. Overall, precipitation chances will begin to increase as moisture begins to increase across the region with isolated to scattered diurnal convection each afternoon. && .AVIATION... (12Z TAFS) Issued at 624 AM EDT Tue Jul 1 2025 VFR conditions prevail this morning with some brief MVFR at TRI early. VCSH prevails this afternoon with highest probability for TSRA at terminals between 22z and 03z this afternoon and evening. Behind the thunderstorms and frontal boundary, winds begin to shift to the W/NW with MVFR cigs expected at TYS and TRI through 12z Wednesday. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 88 70 90 68 / 70 40 10 0 Knoxville McGhee Tyson Airport, TN 88 70 88 67 / 80 60 10 0 Oak Ridge, TN 86 69 88 66 / 80 50 10 0 Tri Cities Airport, TN 85 67 85 63 / 80 80 20 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...JB LONG TERM....JB AVIATION...JB