textproduct: Morristown

KEY MESSAGES

Updated at 112 AM EDT Sun Sep 20 2026

- Well above normal temperatures to persist into early this week. But relief is on the way, with a pattern change expected mid-week and much cooler temperatures to follow.

- Expect isolated to scattered showers today, with increasing coverage Monday through Wednesday.

- A few strong to severe storm with damaging winds could occur today and Monday, with damaging winds being the primary threat. Localized flooding will be possible each day through Wednesday as well.

DISCUSSION

Issued at 112 AM EDT Sun Sep 20 2026

An upper ridge, still centered over the Arklatex, will continue to weaken on Sunday. Despite lowering heights, I would expect there to be less shower and thunderstorm coverage today versus the last couple of days thanks to a lack of forcing mechanism and slightly lower low level moisture and PWATs. There will be convection, just not as much. An isolated strong to severe storm and damaging wind threat, or some localized heavy rains, can't be ruled out. But, the threat is quite low and I would expect that we will remain in the general thunder area in SPC's Day 1 convective outlook. For Monday, expect a marked increase in convective activity as a weak upper low shifts east from the plains into the Ohio valley. Forecast soundings suggest afternoon MLCAPE values will range from around 1,500 J/kg to over 2,000 J/kg area wide Monday afternoon. PWATs will increase a bit too, all of which will support some isolated damaging wind gusts from collapsing storms. Storm motions will be slow too, so localized heavy rains and flooding could be an issue too. Tuesday should feature fairly widespread showers too, but instability looks far less so the severe potential looks negligible.

Lastly, despite the waning influence of the ridge, there's no air mass change until the mid-week time frame. So temperatures will remain well above normal Sunday through Tuesday. Highs in the upper 80s to mid 90s are on tap for Sun and Mon, with low 80s to low 90s for Tuesday. Barring any unforeseen circumstances, Chattanooga looks to continue it's record setting streak of 90 degree days and should top out at 50. Wednesday is the first day of sub-90 forecast highs.

Speaking of Wednesday, and a break in the heat...late Tuesday into Wednesday a rex block pattern sets up, with the upper ridge building on the Canadian side of the Great Lakes, and the upper low re-intensifying south of the ridge over the Ohio valley. This will result in surface high pressure well to our north, and northerly low level flow pushing a cold front through the region sometime on Wednesday. We'll still be warm...maybe 1-3 degrees above normal as opposed to +12-15 degrees...but rain and cloudy conditions will be a welcome change. We'll wrap the week with temperatures around or slightly below normal with highs in the 70s to 80s, and lows in the 50s may even make an appearance by week's end.

AVIATION

(06Z TAFS) Issued at 112 AM EDT Sun Sep 20 2026

VFR throughout for TYS and CHA. For TRI, areas of fog likely to develop overnight and dissipate after sunrise. Similar pattern as the previous few days supports locally dense fog. IFR or worse VSBY/CIGs likely. Isolated showers and thunderstorms possible Sunday afternoon, coverage remains uncertain with TRI most likely to see any RA/TSRA. Maintained PROB30 as a result. TYS and CHA remain VFR with scattered afternoon Cu. Light and variable winds throughout.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 96 72 96 70 / 20 10 40 60 Knoxville McGhee Tyson Airport, TN 93 70 92 69 / 20 10 40 60 Oak Ridge, TN 92 69 92 68 / 20 10 50 60 Tri Cities Airport, TN 88 66 88 65 / 40 10 50 50

MRX WATCHES/WARNINGS/ADVISORIES

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