519
FXUS64 KHUN 211432
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
932 AM CDT Tue Jul 21 2026

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

.KEY MESSAGES...
Updated at 932 AM CDT Tue Jul 21 2026

 - A Heat Advisory is in effect for most of the Tennessee Valley
   through 8 PM.

 - Major (Level 3/4) Heat Risk will develop across the Tennessee
   Valley today, with peak heat index values between 105 to 110
   degrees likely in many locations.

 - Low chance for a few strong to severe storms tonight into early
   Wednesday morning along and ahead of a cold front. Gusty to
   damaging winds, frequent lightning, and locally heavy rainfall
   will be the main threats.

&&

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 932 AM CDT Tue Jul 21 2026

Major (Level 3/4) Heat Risk will continue today across the
Tennessee Valley as an upper-level ridge of high pressure (and the
subsequent heat dome) builds into the region from the west. This will
promote mostly sunny and very warm conditions across the region on
this afternoon/evening, with southerly flow helping to push high
temperatures into the mid 90s in most locations. Combined with
dewpoints in the upper 70s, this will create heat index values
between 105-110 degrees across a vast majority of the Tennessee
Valley. As a result, a Heat Advisory is in effect through 8 PM
this evening.

Upstream from us, a cold front along the Ohio River will serve as
a focus for showers and thunderstorms late this afternoon into the
evening hours. Latest guidance all hits a late arrival for the
Tennessee Valley (10 PM to 5 AM) late this evening and overnight.
It`s unclear as to how supportive the storm environment will be
during this timeframe as any surface-based instability will be
very limited as will low/mid-level lapse rates. Still these
outflow/cold pool driven storms could still be strong to
marginally severe as they move in, especially for locations north
of the Tennessee River where SPC has denoted a Marginal Risk
(Level 1/5) for localized gusty, damaging winds. This is a
conditional threat and it`s entirely plausible that storms weaken
as they approach and we end up getting a minimal amount of
convection and precipitation. We`ll have to watch trends closely
over the next 12-18 hours and adjust PoPs/timing accordingly.

&&

.SHORT TERM...
(Wednesday through Thursday)
Issued at 932 AM CDT Tue Jul 21 2026

On Wednesday, the aforementioned cold front will be pushing
through the region during the morning into the early afternoon
hours. The storm environment should be fairly worked over thanks
the activity overnight into the early morning hours as surface-
based instability will be far more limited. However, a low-
medium (30-60%) chance for showers and a few storms will exist
through the afternoon (especially for locations south of the
Tennessee Valley where instability will be slightly higher). The
aforementioned rain chances and denser cloud cover will lower
temperatures and subsequently heat index values slightly. Still,
highs in the upper 80s to lower 90s, and heat index values around
the 100 degree mark could create some Moderate (Level 2/4) heat
risk concerns.

A slightly cooler and drier air mass will filter into the area in
wake of the front on Thursday, with high temperatures dropping
into the mid to upper 80s and any appreciable precipitation
chances remaining just to the south of the area along the front.
As a result, most of the region will be devoid of any diurnally
driven convection, save for a low chance (20-30%) clipping our far
southeastern zones.

&&

.LONG TERM...
(Thursday night through Monday)
Issued at 905 PM CDT Mon Jul 20 2026

The general upper level setup will consist of a ridging west and
troughing east pattern over the greater North American domain. This
pattern was being kept in place by Omega-style upper blocking over
the northern Pacific basin. At the beginning of the extended, upper
troughing will be in place off of the west coast (the eastern anchor
of the upper block), with strong upper level ridging situated over
the southern Great Plains. A passing upper low over the central
Ontario and Quebec region will deepen, and help amplify upper
troughing from the eastern Great Lakes to northern Florida. This will
place the Tennessee Valley in a WNW-ESE flow from the late week into
early next week.

A northwesterly upper level flow across this area, especially if it
is disturbance laden, is known for bringing showers and thunderstorms
to the Valley. Convection in these regimes can be accompanied by
strong winds. For this area, a few complications to that simplistic
view. First, a cold front should be south of the area by late Thu.
Moisture from Tropical Storm Bertha should be streaming back to the
NE, with some of it impacting the area Fri into Sat. Along with lower
level tropical moisture, some of the extended guidance was suggesting
that upper level support moving across the area from late Fri into
Sun could bring more thunderstorms to the area. It is way too early
to discern if this convection could become more significant, given
much model uncertainty this far out. With a main synoptic front to
our south and with some shower/storm chances, daily high/low
temperatures should trend a bit milder, with highs Fri/Sat in the mid
80s to around 90. Warmer conditions look return for the start of the
new week, with highs from the upper 80s to lower 90s Sun, and low/mid
90s next Mon. Lows Thu night should range in the mid/upper 60s, with
mainly lower 70s for the Fri - Sun night period.

&&

.AVIATION...
(12Z TAFS)
Issued at 610 AM CDT Tue Jul 21 2026

VFR conditions are expected at both terminals through much of the
TAF period. Southerly winds will increase to between 5 and 10
knots this morning before turning more to the southeast this
evening. Confidence is low that any -TSRA will impact either the
KHSV or KMSL terminal through at least 3Z (maybe as late as 6Z).
However, a PROB30 group for -TSRA was included between 5Z and 11Z
for both terminals that lowers VSBYS and CIGS at times to MVFR
criteria. This may need to be shifted as we get closer to that
timeframe or be made more predominant. For now, confidence is just
too low to do anything more than a PROB30 group.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory until 8 PM CDT this evening for ALZ001>009-016.

TN...Heat Advisory until 8 PM CDT this evening for TNZ076-096-097.

&&

$$

NEAR TERM...AMP.24
SHORT TERM....AMP.24
LONG TERM....RSB
AVIATION...KTW