textproduct: Morristown

KEY MESSAGES

Updated at 145 PM EDT Mon May 4 2026

- Widespread showers and storms Tuesday night through Thursday morning.

- Periods of heavy rain are likely. Some flooding concerns are possible given the potential for training showers and storms on Wednesday.

- A conditional severe weather threat exists on Wednesday if surface-based instability can develop.

DISCUSSION

Issued at 145 PM EDT Mon May 4 2026

Main concern for the next 7 days will be the system moving through the region on Wednesday so the discussion will focus on that. This will bring with it the possibility of some flash flooding concerns, as well as a conditional severe weather threat. Gusty winds will be possible in the mountains Tue night into Wed thanks to a strong low level jet, but otherwise mostly dry conditions are in store for the forecast area through the period.

A synoptic scale trough will drop out of central/eastern Canada into the northern CONUS today and tonight, while a closed upper low slowly moves ashore over southern California. Eventually the upper low opens up and anchors the western periphery of the Canadian trough, allowing the northern and southern stream jets to merge over the central CONUS Tue into Wed. The result will be widespread southwesterly flow developing over the deep south and lower Mississippi river valley tonight through the mid week time frame. At the surface, cyclogenesis will take place across the southern plains on Tuesday, with a cold front setting up somewhere from the Arklatex region ENE into eastern Kentucky by Tue night. All of this will lead to a plume of Gulf moisture surging northeast from the Texas coast into the Appalachian region, with PWATS exceeding 1.75" across parts of the area by Wed afternoon before the cold front pushes through Wed night into early Thu morning.

Flooding/Flash Flooding concerns:

Low and mid level flow will be parallel to the front as it approaches, with several waves of surface low pressure forecast to develop and move northeast along the front Tue night through Wed. All of this points to a slow moving boundary which, when coupled with a modest amount of instability, sufficient shear, and high PWATs will mean a chance of training showers and thunderstorms capable of producing heavy rains and some flash flooding issues. The heaviest rain looks to be focused on areas south of the I-40 corridor, which is where drought conditions are the most severe at the moment. And although rain is needed, heavy rains on drought stricken soil is not ideal. Currently the forecast calls for 2-3" of storm total rain across the southern half of the forecast area and especially in the southern TN mountains, which is supported by ensemble data showing very high odds of exceeding 1.5" across a large swath of the southern half of the CWA Tuesday night through Wednesday night. And given the pattern, I would not be at all surprised to see this exceeded in spots if there is any decent training of thunderstorms. Furthermore, WPC has the southern parts of the CWA highlighted by a Day 3 Excessive Rain Outlook, so this all seems reasonable.

Severe weather concerns:

Depending on the location of the front Wed afternoon and evening, and the thermal profiles in place, there could be just elevated instability with heavy rains and no real threat of severe storms. Or there could be the potential for damaging winds and even a conditional tornado risk in the south. Joint probabilities from ensemble data show about a 30-35 percent chance of having surface- based instability exceeding 500 J/kg and bulk shear of 40kt or greater Wed afternoon and evening across the southern TN valley. I don't have high confidence in exactly how this will play out because that will depend on mesoscale details that we're not privy to just yet (e.g. where and when do the waves of surface low pressure develop along the front and pass by/through our CWA, and what are the effects on the low level thermal profiles). However, there's plenty of shear in place and if we can develop surface based instability then damaging winds and even a tornado can't be ruled out over the southern valley and plateau areas Wed afternoon and evening. Currently the far south is outlooked in a Day 3 Marginal risk area by SPC and that seems reasonable given the uncertainties. I wouldn't be surprised if there is an increase in severe chances over the next 24 hours though as the event comes into view of the CAM guidance.

AVIATION

(18Z TAFS) Issued at 107 PM EDT Mon May 4 2026

VFR conditions expected at all sites through the period. Aside from gusty south-southwest winds at TYS this afternoon, winds should be around 10kts or less through the period and mostly south-westerly.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 54 79 63 77 / 0 20 50 80 Knoxville McGhee Tyson Airport, TN 54 79 61 75 / 0 20 70 90 Oak Ridge, TN 52 77 60 73 / 0 20 70 90 Tri Cities Airport, TN 48 78 58 74 / 0 10 60 90

MRX WATCHES/WARNINGS/ADVISORIES

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