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KEY MESSAGES

Updated at 747 PM EDT Mon May 25 2026

- Showers and storms are expected later today and tonight. These will be efficient rainfall producing storms, with the ability to produce localized torrential downpours and flash flooding. Similar conditions will exist Tuesday. - Drier air begins to approach from the north for Thursday onward. Current forecast maintains rain chances area wide through the weekend, but the trends support a drier pattern, at least across the north, as we head into the weekend.

DISCUSSION

Issued at 143 PM EDT Mon May 25 2026

The next 48 hours will feature continued south-southwesterly flow aloft as we remain situated between a once-closed upper low over Texas that will open up and drift north into the mid-Mississippi river valley, and a subtropical ridge aloft centered off the southeast coastline. Guidance shows high PWAT air continuing to stream north from the Gulf into the Tennessee valley and southern Appalachian region during this time. They're highest today through tonight (upwards of 1.8-1.9" depending on the guidance source you look at), but remain above the 90th percentile even into early Wednesday before drier air impinges on the CWA from the north due to a deepening upper trough over the northeast CONUS and associated northerly low and mid level flow. The latter part of the week well be drier and slightly cooler as a result of that deepening trough to our north.

Regarding this afternoon through tonight, regional radar imagery this afternoon shows a couple of MCVs lifting north from the Gulf coast. One is in central Mississippi, just west of the MS/AL state line, while another is moving north off the Gulf coast and will be approaching Hattiesburg in the next few hours. Guidance shows multiple rounds of convection developing over the region out in advance of these features, possibly interacting with a stalled frontal boundary in place across the TN valley. Forecast soundings show prime warm rain processes through late tonight, with skinny CAPE profiles with meager values, high freezing levels, and high PWATs. Surface observations upstream support this and have shown observed 2"/hr rainfall rates with rather unimpressive looking showers and thunderstorms in some cases. Locally current 1hr flash flood guidance in the TN valley ranges from maybe 1.5" in portions of the southern valley, to less than 1" in the northern valley near the I-81 corridor. Even the 3hr FFGs are less than 2" across the board really. So I feel confident in having the flash flood watch out for a good chunk of our CWA through late tonight. To be clear, the flooding threat is isolated versus widespread. But I think it is justified given what occurred yesterday. The main question is whether it needs to be extended to cover the convection that is likely tomorrow in essentially the same air mass and synoptic setup. PWATs are slightly less tomorrow, but still above the 90th percentile for this time of year, and we'll likely have convection associated with that trailing MCV lifting into northern AL and the southern Cumberland plateau (or somewhere in that general area) tomorrow morning. Will let the evening shift make the decision on whether to extend or not, but don't be surprised if it is.

This wet pattern continues into Wednesday, but PWATs begin to decline by that time and both convective coverage and intensity should follow suite.

Again, as mentioned, the latter parts of the week will see a trough deepen across the northeast CONUS and subsequently drier northerly flow begin to spread into the CWA. Current NBM guidance maintains some rain chances over much of the CWA Thu onward, with the higher chances in the south. That seems reasonable for the time being, but deterministic guidance is already showing the focus of rainfall chances shifting south in response to the drier air so I wouldn't be surprised to see those PoPs come down as time goes on...especially across the northern parts of the CWA.

AVIATION

(00Z TAFS) Issued at 747 PM EDT Mon May 25 2026

Additional rain is moving south to north across the southern half of the area currently, and is expected to continue to sweep to the north through the next several hours. Overnight CIGs are pretty uncertain, observations to the south are better than what would otherwise be expected, and guidance is split on how poor conditions trend overnight. Persisted the bulk of the previous TAFs. Categorical conditions should improve by 18z tomorrow though with the caveat of another round of scattered RA and TS to begin thereafter.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 66 79 66 82 / 90 80 80 90 Knoxville McGhee Tyson Airport, TN 65 80 65 81 / 80 70 80 90 Oak Ridge, TN 64 79 64 81 / 90 80 80 100 Tri Cities Airport, TN 62 81 62 80 / 60 80 60 90

MRX WATCHES/WARNINGS/ADVISORIES

NC...Flood Watch until 3 AM EDT Tuesday for Cherokee-Clay.

TN...Flood Watch until 3 AM EDT /2 AM CDT/ Tuesday for Anderson- Bledsoe-Blount Smoky Mountains-Bradley-Cocke Smoky Mountains-East Polk-Grainger-Hamblen-Hamilton-Jefferson- Knox-Loudon-Marion-McMinn-Meigs-North Sevier-Northwest Blount-Northwest Carter-Northwest Cocke-Northwest Greene- Northwest Monroe-Rhea-Roane-Sequatchie-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi-Washington TN-West Polk.

VA...NONE.