Heat in Tennessee, August 18, 2025

Area Forecast Discussion
National Weather Service Huntsville AL
200 PM CDT Mon Aug 18 2025

...New NEAR TERM...

.NEAR TERM...
(Tonight)
Issued at 200 PM CDT Mon Aug 18 2025

Under the influence of sfc high pressure, our area remains dry
today with very low chance (less than 10%) of any shower
development this evening. Fog development should be limited to
along rivers and in sheltered valleys as winds remain light with
mostly clear skies. Low temperatures are forecast to drop into the
low to mid 70s, which is not much relief from the daytime highs in
the 90s we continue to experience. A Heat Advisory remains in
effect through 8 PM Tuesday. Be sure to stay hydrated, avoid
strenuous outdoor activities, and never leave pets/people in
vehicles!

&&

.SHORT TERM...
(Tuesday through Thursday)
Issued at 819 AM CDT Mon Aug 18 2025

Lack of synoptic forcing will keep rain chances low (30% or less)
through most of the short term period. If showers/storms develop,
they will be during the peak afternoon heating hours and will be
scattered in nature. Sufficient instability (sfc CAPE ~1000 J/kg)
and low level lapse rates (~9 C/km) will allow threats with any
storms to include frequent lightning as well as gusty winds up to
40-50 mph. Lack of wind shear should prevent any organized severe
development of storms. Heat will continue to be a concern through
at least Tuesday evening, during which our Heat Advisory remains
in effect for high temperatures in the mid to upper 90s and heat
indices up to 107 (primarily along and west of I-65). We drop
below Heat Advisory criteria Wednesday, however, it will still be
hot with highs in the 90s and heat indices up to 100-104 with
isolated areas up to 106. If these temperatures trend higher in
future forecast updates, the Heat Advisory may be extended. Be
sure to stay hydrated, limit strenuous outdoor activities, wear
light-colored clothing, and check on friends/family.

Wednesday into Thursday, weak upper level troughing and a cold
front stemming from the Great Lakes region is forecast to
influence the area. There is a low chance this front evolves into
an MCS, which would increase the risk for locally damaging winds
and heavy rainfall. We have low confidence in exact timing of this
at this moment due to some slight model disagreement. The timing
of this will also affect temperatures Wednesday if it moves in
earlier, and could result in cooler temperatures than forecast.
One thing is for certain: a slight cool down is forecast
afterwards as highs should decrease to the upper 80s to lower 90s
with heat indices topping out around 95-100 degrees.

&&

.LONG TERM...
(Thursday night through Monday)
Issued at 819 AM CDT Mon Aug 18 2025

An upper level trough continues to influence the area through the
weekend, bringing increased cloud cover as well as low to medium rain
chances daily. However, this will also result in decreased
temperatures as highs peak in the 80s throughout most of the area.
While we are still too far out to get into specific threats with
any potential thunderstorm development, storms will likely be
capable of producing heavy rainfall as PWATs are forecast to be
around 1.7-1.9", which is around the 75th to 90th percentile per
BMX sounding climatology.

&&

.AVIATION...
(18Z TAFS)
Issued at 1219 PM CDT Mon Aug 18 2025

VFR conditions are forecast through the TAF period at both KMSL
and KHSV.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory until 8 PM CDT Tuesday for ALZ001>007-016.

TN...Heat Advisory until 8 PM CDT Tuesday for TNZ076-096.

&&

NEAR TERM...HC
SHORT TERM....HC
LONG TERM....HC
AVIATION...HC