Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
737 FXUS64 KMRX 302315 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 715 PM EDT Wed Sep 30 2026 ...New AVIATION... .KEY MESSAGES... Updated at 713 PM EDT Wed Sep 30 2026 - Dry and warm conditions are expected through tomorrow with highs well into the 80s to low 90s in the south. - Chances for showers and isolated storms will increase through the weekend with locally heavy rainfall possible. - Drier and cooler conditions will return next week. && .DISCUSSION... Issued at 713 PM EDT Wed Sep 30 2026 Currently, ridging is in place aloft with a closed low ejecting into the southern Rockies. With high pressure remaining in place across the eastern U.S. and southerly flow, dry and warm conditions can be expected with temperatures well above normal. By Thursday, the closed low will eject into the Great Plains, leading to the development of a surface low and open wave / surface frontal boundary. Locally, ridging will increase with 500mb heights reaching above 5,880m, values typical in July. This makes the case for further surface heating and highs reaching well into the 80s to low 90s in the south. Also, as recent high pressure shifts off to the east, increasing moisture can also be expected. By Friday, the closed low/shortwave will lift to the northeast with the frontal boundary approaching from the northwest ahead of Canadian high pressure. With continued moisture advection, this pattern will produce widespread rain chances through the weekend as the front stays near or north of the area. PWAT values will reach above 1.6 inches, which is above the 90th percentile, suggesting locally heavy rainfall rates are possible. There are also indications of some elevated instability early in the weekend, which would be sufficient for at least low-end chances for convection. Overall QPF totals have decreased, but there is still a low probability for hazardous weather for isolated flooding. Early next week, a pattern shift is expected as high pressure expands from the north, pushing the front south of our area. This will lead to northerly flow and cooler and drier conditions, especially at night. At this time, models differ on the southward extent of this frontal boundary progression, which would affect how much cooler of conditions are expected. && .DISCUSSION... Issued at 233 PM EDT Wed Sep 30 2026 Currently, ridging is in place aloft with a closed low ejecting into the southern Rockies. With high pressure remaining in place across the eastern U.S. and southerly flow, dry and warm conditions can be expected with temperatures well above normal. By Thursday, the closed low will eject into the Great Plains, leading to the development of a surface low and open wave / surface frontal boundary. Locally, ridging will increase with 500mb heights reaching above 5,880m, values typical in July. This makes the case for further surface heating and highs reaching well into the 80s to low 90s in the south. Also, as recent high pressure shifts off to the east, increasing moisture can also be expected. By Friday, the closed low/shortwave will lift to the northeast with the frontal boundary approaching from the northwest ahead of Canadian high pressure. With continued moisture advection, this pattern will produce widespread rain chances through the weekend as the front stays near or north of the area. PWAT values will reach above 1.6 inches, which is above the 90th percentile, suggesting locally heavy rainfall rates are possible. There are also indications of some elevated instability early in the weekend, which would be sufficient for at least low-end chances for convection. Overall QPF totals have decreased, but there is still a low probability for hazardous weather for isolated flooding. Early next week, a pattern shift is expected as high pressure expands from the north, pushing the front south of our area. This will lead to northerly flow and cooler and drier conditions, especially at night. At this time, models differ on the southward extent of this frontal boundary progression, which would affect how much cooler of conditions are expected. && .AVIATION... (00Z TAFS) Issued at 713 PM EDT Wed Sep 30 2026 Outside of morning fog chances at TRI... VFR conditions expected the next 24 hours. Fog will form along the river/lake near the TRI airport, but will it make it to the runway is the big question. It got close this morning so have gone with a persistence forecast with borderline MVFR visibilities around sunrise. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 63 92 68 92 / 0 0 0 40 Knoxville McGhee Tyson Airport, TN 59 89 66 89 / 0 0 0 50 Oak Ridge, TN 59 88 65 87 / 0 0 0 50 Tri Cities Airport, TN 56 84 60 85 / 0 0 0 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...BW AVIATION...99