139 
FXUS64 KMRX 251816
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
216 PM EDT Mon May 25 2026

...New DISCUSSION, AVIATION...

.KEY MESSAGES...
Updated at 143 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...
(18Z TAFS)
Issued at 143 PM EDT Mon May 25 2026

The 18z TAF package is basically a persistence forecast of the
last 24 hours, with another round of SHRA and ISOLD TSRA expected
across East Tennessee this evening and resulting flight 
categories dropping to at least MVFR levels overnight. Guidance
continues to seem too pessimistic with regards to VSBY so I kept
it limited to MVFR. Same for CIGS, although some BKN050-070 CIGS
seem plausible in the stable conditions between rounds of showers
later tonight. Not highly confident on that so have just left a 
SCT007 in at KCHA and KTYS.

&&

.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 through late tonight for Cherokee-Clay.

TN...Flood Watch through late tonight 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.
&&

$$

DISCUSSION...CD
AVIATION...CD


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