textproduct: Morristown

KEY MESSAGES

Updated at 721 AM EDT Tue Jul 21 2026

- Cold frontal passage today into tomorrow may bring several rounds of showers and storms, with a wide range of potential outcomes. See disc below.

- There's some uncertainty, but the cold front may stall to the south, continuing showers and storms for parts of the forecast area until the latter part of the week. This could pose some flooding impacts.

- Below normal temperatures will follow beyond Wednesday until the early part of the weekend. Gradual warming to near normal early next week.

DISCUSSION

Issued at 124 AM EDT Tue Jul 21 2026

The bulk of this discussion will focus on the today through tomorrow timeframe. There is a high level of uncertainty regarding the timing and potential impacts during this timeframe, as there are various model solutions. Generally though, we are looking at the possibility of several rounds of showers and storms with the potential of strong to severe storms from later this morning through tomorrow morning.

Tropical Storm Bertha became officially named as of last night. Even though she will remain well to our south in the Gulf, her presence and slow movement westward may impact how things move and progress for today into tomorrow. From her current location off of the FL Peninsula coast, she will be located near New Orleans tomorrow morning. Part of the reason for her movement is because of weak flow/steering over much of the southern U.S.. The highest heights of the upper ridge will sink towards Texas with time, aiding Bertha to somewhere in the western Gulf later this week.

The pattern of high amplitude ridging to the west and troughing with shortwave impulses to the east continues. Multiple shortwave impulses will round the bottom of the trough before it's carried into far NE Canada later tomorrow into Thursday. At the surface, a cold front currently draped over IL to IA to NE/KS will eventually shift our direction, impacting us well before it even arrives. The actual front itself may not arrive until early tomorrow.

The potential impacts from today may come from at least three separate rounds of showers and thunderstorms. Each round may become stronger as the front gets closer and we introduce higher shear. Because of this possibility, it may impact the severity and evolution of the next round, so uncertainty is on the lower side. Runs of recent CAMs cannot totally grasp it or even try to align with one another. In the next couple of hours or so, some isolated to scattered showers and possible thunderstorms may develop across our northern tier. They will most likely mimic what we've seen the past couple of days with high PWATs and low overall shear. There may be a period of drying or there could be continuing activity until the next round.

Activity for the most part will be shifting down from the north and northwest. Later this afternoon and evening could introduce the next round where we will be at peak heating. Everything up until this point is pre-frontal. The main threats from storms will be damaging wind gusts and potential flooding issues. After dark, or the next round, will confidently be the period with the least confidence and certainty. Better shear rolls in as well as SRH, but surface instability falls off some after peak heating. CAMs disagree on timing of arrival as well, which Bertha may be partly to blame. Damaging wind gusts will continue to be the greatest threat with a general linear storm mode. If we can generate hail, it will most likely be of the smaller variety. A low-end tornado threat does exist, mainly for the northern plateau into southwest VA. Unless there's some localized effects, backed surface winds may be hard to accomplish.

The "third" round may begin as early as 7 PM EDT, persisting through the overnight hours until it weakens. Movement during the overnight, at least according to CAMs, doesn't show much southern progression, so that puts flooding on the forefront of impacts. Generally, north of I-40 and the higher terrain can expect the higher end of QPF.

Later tomorrow into Thursday, when previously thought that it would dry out, may keep chances of showers and storms around with the potentially stalled front to our south, Bertha just off of the LA coast, and high pressure desperately trying to barrel in from the north. WPC recognizes this, keeping MRGL to SLGT ERO tomorrow into Thursday.

The weekend as far as precipitation goes, does become more uncertain with a shortwave approaching from the northwest while the front may still be hung up to our south. We can say with certainty though, that temperatures tomorrow and into the first part of the weekend will be noticeably below normal with low and mid 80s. Temperatures gradually warm to near normal values early next week.

AVIATION

(12Z TAFS) Issued at 721 AM EDT Tue Jul 21 2026

Winds will become gusty from the SW at TYS this afternoon. In the evening, showers and storms are expected to move south from KY, with the time of arrival at TRI expected to be around midnight. Showers and storms may continue through the night at TRI as a front stalls nearby. There is uncertainty about whether storms will get to TYS in this TAF period, so will leave storms out of that TAF for now.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 94 76 89 70 / 0 40 80 40 Knoxville McGhee Tyson Airport, TN 92 74 86 68 / 10 80 80 30 Oak Ridge, TN 91 73 86 66 / 20 90 70 10 Tri Cities Airport, TN 88 69 83 63 / 40 90 80 20

MRX WATCHES/WARNINGS/ADVISORIES

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