textproduct: Morristown

DISCUSSION

Issued at 106 AM EDT Sun Aug 31 2025

Key Messages:

1. Warmest temperatures of the week will be today. Slightly cooler Monday, but will generally fall below 80s for highs the rest of the week.

2. Isolated to scattered showers and storms possible across the eastern higher terrain this afternoon and evening.

3. For Monday into Tuesday, isolated to scattered showers and storms will favor the plateau. A cold front sometime around Thursday, will bring better precipitation chances elsewhere.

Discussion:

Surface high pressure is centered over the Great Lakes region, meanwhile, two stationary boundaries are locked to the south. Increased humidity today and thus, instability, will promote isolated to scattered showers and thunderstorms over the higher terrain from southwest North Carolina up into southwest Virginia this afternoon and evening. A fairly low-end threat for any robust storms with CAPE values struggling to exceed 500 J/kg, and PWATs hardly around an inch or less. Deep layer shear could sustain shower or storm longevity given values of 25 to 35 kt plus or so.

Under continuous northwest flow, a newly developed closed low will separate from the much stronger one eventually moving off of the NE US. This will broaden the troughing over the central and eastern US, while lowering our heights aloft Monday. Cooler temperatures can be expected under cloudier skies. Weak shortwave troughing will bring isolated to scattered precipitation primarily to the plateau and parts of the eastern higher terrain Monday into Tuesday. Before a cold front reaches the area sometime between late Wednesday and early Friday, return flow and a stronger shortwave will bring a greater than 40% chance for showers and storms to the forecast area on Wednesday. A deepening trough is forecast to move SSE out of Canada, centering over Lake Superior or so before curving back north. A cold front originating from the northern Plains will sweep through around the Thursday timeframe, providing the area with yet another day of at least scattered showers and storms. The forecast period may round out at the end of the week dry behind the frontal system.

Temperature-wise, today may be the warmest of the week with the just below normal readings continuing. Slightly cooler on Monday before values tumble lower than 80 Tuesday and Wednesday. A slight increase in temperatures for the first weekend of September, but not without much cooler morning lows.

AVIATION

(12Z TAFS) Issued at 700 AM EDT Sun Aug 31 2025

Main concerns are potential of mid to late afternoon showers and possibly a thunderstorm, and fog/low-cloud develment early Monday morning near TRI. An inverted surface trough axis will develop across the southern Appalachians. Marginal instability with MLCAPEs up to 500. The convection should be east of TYS and CHA.

Steam fog development off Boone Lake may drift across TRI early Monday morning. Also, if a shower occurs at the airport late today the threat of fog increases.

Otherwise, VFR conditions are expected even though periods of mid to high level clouds anticipated. At TRI broken ceiling of 5-6 kft mid to late afternoon with the showers.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 86 64 83 64 / 10 10 20 20 Knoxville McGhee Tyson Airport, TN 83 61 82 62 / 10 10 10 20 Oak Ridge, TN 83 60 81 61 / 10 0 20 20 Tri Cities Airport, TN 79 55 79 54 / 20 10 0 0

MRX WATCHES/WARNINGS/ADVISORIES

NC...NONE. TN...NONE. VA...NONE.