443
FXUS64 KHUN 211353
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
853 AM CDT Mon Sep 21 2026

...New NEAR TERM, SHORT TERM...

.KEY MESSAGES...
Updated at 853 AM CDT Mon Sep 21 2026

 - The coverage of showers and thunderstorms will remain fairly
   high through Tuesday. Conditions will be favorable for strong-
   severe thunderstorms, particularly this afternoon/evening and
   again on Tuesday afternoon. Locally damaging downburst winds,
   frequent lightning, and heavy rainfall will be the main
   hazards.

 - A slightly cooler and drier airmass will begin to arrive on
   Wednesday. Highs will fall back into the lower-mid 80s from
   Thursday-Sunday, with lows in the mid-upper 50s this weekend.
&&

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 853 AM CDT Mon Sep 21 2026

As an upper level trough and subsequent sfc low pressure system
shift southeastward toward the Tennessee Valley, our environment
remains favorable for thunderstorm development this afternoon into
the evening hours. MLCAPE values are forecast to comfortably reach
1200+ J/kg along and east of I-65, accompanied by DCAPE near
800-900 J/kg as well as steep low level lapse rates. Dew points
will reach the upper 60s to low 70s with subsequent PWATs in the
1.6-1.8" range (near 90th percentile per BMX climatology).
Therefore, our primary concern will be downburst gusty to
damaging winds (40-60 mph) in addition to frequent lightning and
heavy rainfall. Storm speed should be slow (similar to the past
several days, remaining around 5-10 mph) which will cause ponding
of water in areas of poor drainage in areas where storms form.
CAMs are initializing very poorly, however, this will likely fall
in the timeline of diurnally fueled convection with the main
window for storms being 2 PM - 8 PM CT. There is a low chance a
few thunderstorms persist past 8 PM into the late night hours, but
these should be below severe limits with the loss of daytime
heating. Despite parameters being more favorable along and east of
I-65, a low chance for severe weather remains in place for all of
northern AL and southern middle TN. SPC has outlooked the area in
a Marginal risk (level 1 of 5) for severe weather, with damaging
winds being the primary hazard. Be sure to have multiple ways to
get warnings this afternoon into the evening hours.

Heat, on the other hand, should be slightly less of a threat today
with more widespread thunderstorm formation/cloud cover. Highs are
forecast to reach the upper 80s to mid 90s with heat indices
remaining 100 degrees or less. A Moderate HeatRisk (level 2 of 4)
still exists, so be sure to remain hydrated and seek shade when
outdoors.

&&

.SHORT TERM...
(Tuesday through Wednesday night)
Issued at 853 AM CDT Mon Sep 21 2026

As the aforementioned low pressure system continues into the
Tennessee Valley, continued forcing for thunderstorms will exist
with the primary concern being damaging winds yet again. As of
now, SPC has outlooked the southeastern portions of our CWA in a
Marginal risk (level 1 of 5) for severe weather due to the
potential for damaging winds. Similarly to Monday, MLCAPE values
of 1000-1200 J/kg with DCAPE around 600-800 J/kg and steep low
level lapse rates will support a risk of gusty to damaging winds
(40-60 mph). Parameters look slightly less favorable Tuesday than
they will be today (Monday) so slightly less confident in the
overall severe threat. Additionally, as the sfc low pushes
southeast through the area, coverage should also be more limited
with the bulk of activity remaining where the current SPC outlook
resides (primarily in NE AL). Timing for this should line up with
diurnal support once again with the peak storm potential being
between 2 PM - 8 PM. Low chances for thunderstorms will continue
to linger overnight, however, support of daytime heating will be
lost and storms should remain sub severe.

The frontal boundary will likely briefly stall to our southeast,
which will allow low chances for rain to continue in our eastern
areas through Wednesday. We are not outlooked for severe weather
at this time and confidence remains low in strong storm formation
behind the boundary. Dry weather should fully return to the
forecast Thursday.

Temperatures during the short term are forecast to gradually
decrease with highs being capped in the low to mid 80s by Thursday
and overnight lows dropping into the lower 60s by Thursday
morning. Don`t get too excited about the cooler temperatures, as
the CPC continues to outlook us for above normal temperatures in
the extended range.

&&

.LONG TERM...
(Thursday through Sunday)
Issued at 1101 PM CDT Sun Sep 20 2026

Global models suggest that a weak mid/upper-level low (initially
across the central Appalachians) will phase with a smaller
disturbance to its east later this week to form a deep low that
will sit off the northern Mid-Atlantic Coast this weekend. This
will ensure a continuation of dry NNW flow aloft across the TN
Valley for much of the period, before this regime weakens Saturday
and Sunday. With indications that low-level confluence across
will progressively diminish on Thursday/Friday, the risk for
showers in the east will continue to fall as light N-NE flow
advects a drier airmass into the region from a high across
southeastern Canada. Highs will be in the l-m 80s, with overnight
lows dropping into the m-u 50s this weekend (when dewpoints could
drop into the 40s).

&&

.AVIATION...
(12Z TAFS)
Issued at 618 AM CDT Mon Sep 21 2026

VFR conditions will largely prevail through the TAF period. The
exception will be if heavier showers/stronger storms move over the
terminals today and this evening, bringing periods of lower CIGs
and VIS. The main timeframe for strong/severe storms is this
afternoon and evening (generally between 1-10PM), with damaging
winds, frequent lightning, and heavy rain the main threats.
Activity is likely to diminish through midnight tonight, with
little to no showers/storms overnight. There is a low chance of
patchy fog tonight, especially for locations that receive
rainfall. However, confidence is too low to include in the TAFs at
this time. Otherwise, expect light and variable winds today and
calm winds later tonight.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&

$$

NEAR TERM...HC
SHORT TERM....HC
LONG TERM....70
AVIATION...26