789
FXUS64 KHUN 220502
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1202 AM CDT Tue Jul 22 2025

...New AVIATION...

.NEAR TERM...
(This Evening through Tuesday)
Issued at 1042 PM CDT Mon Jul 21 2025

The synoptic scale environment across the TN Valley will be
dominated by a mid/upper-level subtropical high throughout the
near term period, as it`s center migrates slowly northward into
the Mid-South region. However, in spite of the unfavorable
environment for convection aloft, low-level streamline confluence
in the vicinity of two boundaries will provide sufficient lift (in
the presence of a very moist airmass) to generate at least a few
showers and thunderstorms through Tuesday.

The first feature of interest is a long outflow boundary
(originating from more widespread convection earlier today to our
north) that currently extends from southeastern MO/southwestern IL
into northeast AL/northwest GA. Although convection along the
southern portion of the boundary has weakened considerably over
the last hour, additional cells along the northern portion of the
convergence axis may tend to spread south-southeastward into our
region during the early morning hours. The second feature of
interest is a backdoor cold front (positioned to the northeast of
the outflow boundary) that will continue to spread southwestward
with time as a Canadian surface high shifts from southern Ontario
into New England.

As the backdoor front begins to intercept the outflow boundary
around sunrise Tuesday morning, it seems reasonable to believe
that this will lead to a notable increase in thunderstorm
activity, beginning initially across western KY and adjacent
portions of northwest and northern Middle TN but developing south-
southeastward into our CWFA after 12Z. Beyond this point,
precipitation coverage for the remainder of the day will be
highest across the southwestern half of the forecast area (to the
south/west of the backdoor front). With the storm environment
characterized by weak shear and abundant moisture (surface
dewpoints in the m-u 70s and PWAT values around or slightly higher
than 2"), locally heavy rainfall and lightning will be the most
significant storm impacts. However, a few brief wind gusts up to
40-50 MPH will be possible with strongest cells (particularly
those occurring during the daylight hours tomorrow). In similar
fashion to today, locations not impacted by convection will see
temps quickly rise into the l-m 90s tomorrow with apparent temps
in the 105-110F range. Thus, the Heat Advisory will remain intact
through 9 PM Tuesday.

&&

.SHORT TERM...
(Tuesday night through Thursday night)
Issued at 1042 PM CDT Mon Jul 21 2025

Latest model data suggests that the TN Valley will remain under
the influence of a strengthening subtropical ridge (centered
across the Mid-South/Lower OH Valley region) from Tuesday night-
Wednesday night, resulting in a lower coverage of showers and
thunderstorms during this timeframe. That said, a few storms will
still be possible on Wednesday both in the higher terrain as well
as in the vicinity of a remnant backdoor cold front (positioned to
our immediate southwest). A greater concentration of storms will
likely evolve across GA and adjacent portions of the southern
Appalachians as a stronger backdoor front begins to send a surge
of drier continental air westward across the southeastern U.S.,
but at this point coverage as far west as northeast AL is
uncertain. Regardless, convection both Tuesday and Wednesday
evenings should dissipate quickly around sunset. Afternoon highs
on Wednesday will once again be in the l-m 90s, and with the
leading edge of the drier continental airmass (dewpoints in the
u60s-l70s) not expected to arrive in our eastern zones until
Wednesday night, another Heat Advisory may be warranted on
Wednesday.

Forecast uncertainty increases on Thursday and Thursday night, as
the northern portion of an easterly wave (undercutting the
subtropical ridge) may at least temporarily diminish the influence
of high pressure aloft during this timeframe. Although this would
only have a minor impact on the overall synoptic environment, it
could potentially support a greater coverage of showers and
thunderstorms Thursday afternoon/evening (especially if the
advection of drier continental air into our region from the east
is less than currently anticipated). With highs only predicted to
reach the u80s-l90s on Thursday, extension of the Heat Advisory is
not expected at this time.

&&

.LONG TERM...
(Friday through Monday)
Issued at 1042 PM CDT Mon Jul 21 2025

The large scale pattern as we head into Friday and over the
weekend will be categorized by high pressure shifting west through
the Gulf Coast region as the broader upper ridge begins to become
better amplified over the Midwest. Unfortunately, this means
there is no end in sight to the heat or daily chances for
thunderstorms. The aforementioned high will track west across the
FL Panhandle on Saturday and there looks to be some northward
extent of the drier airmass accompanying the high. This will bring
a very slight relief in humidity and should help keep afternoon
heat indices below 105 degrees across much of the area. That being
said, highs will still reach the upper 80s/lower 90s and with
dewpoints in the low to mid 70s this will still yield heat indices
between 97-104 degrees. Temperatures look to heat up at the start
of the next work week as the ridge becomes better amplified and
H85 temps will once again be on the rise. With the prolonged
period of dangerous heat, please continue to practice heat safety,
stay hydrated, and check on loved ones and pets that may be
especially susceptible to the heat.

&&

.AVIATION...
(06Z TAFS)
Issued at 1202 AM CDT Tue Jul 22 2025

There have been no significant changes to aviation forecast
reasoning. However, with current radar data indicating
redevelopment of lgt-mod SHRA along a residual outflow boundary,
we have included a TEMPO group for HSV from 6-7Z. In the wake of
any late evening convection, partial clearing and lgt/vrbl winds
may support development of patchy BR/FG early this morning.
Otherwise, convection is expected to redevelop shortly after
sunrise across northern portions of Middle TN and should spread
southwestward over the course of the day in conjunction with a
backdoor cold front. PROB30 groups have been included btwn 15-21Z
to address the potential for storms, with improving conds expected
by late aftn as winds shift to NE.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...Heat Advisory until 9 PM CDT Tuesday for ALZ001>007-016.

TN...Heat Advisory until 9 PM CDT Tuesday for TNZ076-096-097.

&&

$$

NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...70/DD
AVIATION...70/DD