textproduct: Morristown

KEY MESSAGES

Updated at 730 PM EDT Tue Jul 21 2026

- Showers and storms will affect the area tonight into at least Wednesday night. Some of the storms this evening into the first part of tonight may be strong to severe with damaging winds the primary threat along with a low end possibility of a tornado mainly across the northern portions of the area.

- Very heavy rainfall will be possible with a threat of flash flooding tonight through Wednesday night, with the primary threat mainly northern half or two thirds of the area tonight into Wednesday with the threat then shifting southward by Wednesday night.

- Below normal high temperatures can be expected Thursday through Saturday, then temperatures will not be far from normal for the remainder of the period.

DISCUSSION

Issued at 210 PM EDT Tue Jul 21 2026

There is still uncertainty in the details for the tonight through Wednesday night time frame although the envelope of model solutions is narrowing a bit overall as we get closer. Weak short wave energy will be moving through the northeast CONUS upper trough and a summertime cold front will sag southeast toward our area tonight. With the core of the upper jet staying well to our north, the upper support over our area looks weak overall. This leaves us with a less certain scenario more dependent on the timing/location of the summertime front (which is as usual quite difficult to pinpoint in advance) as well as the evolution and movement of upstream convection and related outflow boundaries/cold pool dynamics. That being said, the main two concerns in the short term continue to be the potential for severe storms and also flash flooding.

The potential for severe storms still looks to be highest across our northern areas this evening into tonight. Most of the CAMS show a broken line of convection dropping out of KY this evening but weakening as it moves into our area, with some showing a westward development of the stronger cells following the gradient of higher CAPE which is a plausible scenario. How well convection maintains itself will be critical for our severe threat and is still unclear. The more significant effective bulk shear (around 30 to 40 kts and possibly even briefly higher north) will be across the northern half of our area , and low level hodographs show enough of a clockwise curve to keep the low end threat of a tornado in place providing the convection maintains enough strength. The primary severe threat still looks to be damaging winds. Our northern counties will be the first to be impacted and given the expected weakening trend, would thus be facing the higher severe threat. Also, with the potential for a pivot to the west for the stronger storms our northern Plateau counties would be another location that may see a higher threat. However, strong to severe storms may push well into our area overnight if the weakening trend is slower than most CAMS currently depict.

As for the flooding threat tonight through Wednesday night, models continue to indicate moisture will be plentiful with PWAT values either side of 2 inches for much of the period and CAPE generally exhibiting a tall skinny profile which would favor warm rain processes and high rainfall rates. Placement of convective boundaries and eventually the frontal boundary that will move in but be slow to exit will play a large part in location and timing of the heavy rain threat. Hi-res ensemble data is pointing toward a threat of heavy rain across northern half or two thirds of our area tonight into Wednesday as the northern convection pushes in and likely leaves a residual boundary, and then the front itself pushes in Wednesday. Both the HREF and REFS show bands of very heavy rainfall somewhere across our northern half, with potential for 3 to 5+ inches in some spots tonight through Wednesday. The precipitation focus then shifts further south by Wednesday night as the front slowly sags southward. Given the expected slow boundary movement, training cells will be a concern and this combined with the fact that the ground is still on the wet side across portions of the area from recent rains and flooding, will issue a flash flood watch for roughly the northern two thirds of our area for tonight and Wednesday. Will let later shifts look at whether or not an additional watch is needed for southern areas as the threat shifts south. It is possible that the flooding threat will linger into Thursday across the south as the front struggles to push south of our area although northern areas will likely be mainly dry.

The remainder of the forecast has the basic pattern of upper ridging to our west and troughing over the eastern CONUS continuing. We will see short wave energy moving southeast on the back side of the trough at times that will bring additional showers an storms to our area for the Friday through Tuesday period. Timing of these features and the resulting convection is of course unclear this far out. Temperatures for Thursday into Saturday look to be a bit below normal, then the remainder of the period through Tuesday will likely see temperatures not far from normal for this time of year.

AVIATION

(00Z TAFS) Issued at 730 PM EDT Tue Jul 21 2026

A line of thunderstorms is moving into the region over the next few hours from the north. This line is expected to weaken as it moves into the region. Chances of thunder at each terminal overnight is low but rain is likely at times. Scattered showers will continue through the morning hours and all afternoon tomorrow. Thunder will likely be more isolated. MVFR CIGs and possibly vis will be possible mainly at TRI in the late night and morning hours. Low level wind shear is possible in the late night and early morning hours near TRI but confidence is low.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 76 89 71 86 / 20 60 60 50 Knoxville McGhee Tyson Airport, TN 74 86 68 84 / 60 80 70 40 Oak Ridge, TN 73 86 66 84 / 70 70 50 20 Tri Cities Airport, TN 70 82 64 82 / 100 90 50 30

MRX WATCHES/WARNINGS/ADVISORIES

NC...NONE. TN...Flood Watch from midnight EDT tonight through Wednesday evening for Anderson-Blount Smoky Mountains-Campbell-Claiborne- Cocke Smoky Mountains-Grainger-Hamblen-Hancock-Hawkins- Jefferson-Johnson-Knox-Loudon-Morgan-North Sevier-Northwest Blount-Northwest Carter-Northwest Cocke-Northwest Greene- Roane-Scott TN-Sevier Smoky Mountains-Southeast Carter- Southeast Greene-Sullivan-Unicoi-Union-Washington TN.

VA...Flood Watch from midnight EDT tonight through Wednesday evening for Lee-Russell-Scott VA-Washington VA-Wise.