281
FXUS64 KHUN 201143
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
643 AM CDT Wed Aug 20 2025

...New AVIATION...

.NEAR TERM...
(Today)
Issued at 403 AM CDT Wed Aug 20 2025

Somewhat of a pattern change is on the way as we go into early
next week. Weak upper level troughing currently in place over the
eastern third of the North American domain, will become more
established by the time we reach next week. A few items helping
it include Hurricane Erin, now about 450 miles east of the Space
Coast FL. It will continue heading northward, eventually taking a
NNE turn after passing east of North Carolina, then toward the
northern Atlantic. No impacts are expected across the Tennessee
Valley from Erin. Another upper low currently over British
Columbia should reach southern Ontario by early next week,
establishing a mean troughing pattern over the eastern Lower-48.

For the shorter term, a cold front extending from Lake Erie to
southern Missouri and Nebraska is forecast to move towards this
region tonight. The local atmosphere is still moisture loaded with
dewpoints in the lower 70s. Daytime heating and the approach of
the front will bring moderate to high chances of showers/t-storms
this afternoon and evening. Before convection becomes the dominate
player, a last day of heating, albeit not as intense thanks to
more clouds and lower level moisture in some spots from recent
heavy rainfall will produce an unstable environment. High
temperatures should rise into the low/mid 90s. Dewpoints in the
lower to at times mid 70s with that heat, will produce heat index
values from the mid/upper 90s to 105 in a few spots. Given a much
smaller coverage of the heat and higher uncertainty if the higher
temps will be reached, will hold off on a Heat Advisory today.

Surface based and most unstable CAPEs should rise to 1500-2000
J/kg, along with precipitable water values of 1.7 to over 2
inches. It goes without saying that locally heavy rainfall will be
result when convection gets going. Forecast rainfall amounts from
the blends and WPC look reasonable far as big picture amounts of
1/2 to over an inch this afternoon. But do think locally higher
amounts are possible; (like over 2.5" noted vis backyard stations
east of Florence late Tue evening). More rainfall of this amount
falling in a short time will run off and could produce flash
flooding. As such, the entire area today and tonight is within a
Marginal Risk for excessive rainfall from the Weather Prediction
Center.

Thunderstorm intensity is another issue. Rather high instability
and loading of water aloft in the stronger convection could
rapidly descend to the ground aka microburst style, with an
invert-V in many of the forecast soundings. Strong to damaging
outflow wind gusts appear to be the main threat. The Storm
Prediction Center has much of our southern area within a Marginal
Risk of severe weather. Depending upon when convection forms,
areas a bit more to the north could be under the gun for severe
storms as well.

&&

.SHORT TERM...
(Tonight through Friday night)
Issued at 934 PM CDT Tue Aug 19 2025

Latest short range model data suggests that a cold front will
continue to advance southeastward and into the local forecast area
Wednesday night/early Thursday morning, perhaps leading to a
continuation of showers and thunderstorms across the region
Wednesday evening. However, if sufficient convective overturning
can occur to stabilize the local airmass tomorrow afternoon, the
risk for lingering showers and storms will end rather quickly
around or shortly before sunset. Due to both the presence of a
rain-cooled airmass and weak dry advection in the wake of the
front, lows will be in the u60s-l70s Thursday morning, with
conditions more favorable for development of fog (presuming that
skies become partially clear).

During the period from Thursday-Friday night, low-level
streamlines originating from a surface ridge (extending from the
Upper-MS Valley into the Canadian maritime provinces) will advect
a slightly cooler/drier airmass into our region in the wake of the
front. However, current thinking is that the boundary may
actually stall before exiting our southeastern forecast zones,
providing for both a gradient in moisture and POPs. Within the
drier airmass to the northwest of the front, dewpoints in the l-m
60s and PWAT values in the 1.3-1.4" range will support little (if
any) precipitation. Along and to the southeast of the front, a few
showers and thunderstorms will remain possible. Highs will be in
the u80s-l90s, with lows in the u60s-l70s.

&&

.LONG TERM...
(Saturday through Tuesday)
Issued at 934 PM CDT Tue Aug 19 2025

Through the extended forecast, there will be a daily chance for
showers and thunderstorms that give way to lower temperatures.

The TN Valley will be stuck in weak troughing at the end of the
week into the weekend. A trough axis drifting through the TN
Valley will keep low to medium (20-50%) chances for showers and
thunderstorms on Saturday. On Saturday, a cold front will slide
into the Midwest and Mid MS Valley and on Sunday it will bring one
more low end chance (15-30%) of showers and storms as the front
moves in.

With weak steering flow and elevated PWATS (1.5-1.9"), storms
Saturday could produce gusty winds and heavy rainfall that could
create localized flooding concerns. Behind this frontal passage,
drier air will filter in, bringing a break in the humidity, and
rainfall as Monday and Tuesday will be dry. We will see a steady
decline in temperatures through the extended, starting with highs
in the upper 80s-lower 90s on Saturday and only reaching the lower
80s on Tuesday. By Monday night, lows will only reach the upper
50s to lower 60s, really making it feel like Fall!

&&

.AVIATION...
(12Z TAFS)
Issued at 643 AM CDT Wed Aug 20 2025

At TAF issuance, showers were not occurring over the greater
Huntsville forecast area. But this should change as we go into the
morning, as daytime heating destabilizes an environment loaded
with many outflow boundaries from previous convection. Then a cold
front approaching from the north, will result in scattered to
numerous showers/storms mainly this afternoon and evening. Some of
these storms could become strong to severe in intensity, with
strong, microburst-type outflow winds the main threat. VSBY/CIGs
could be reduced to IFR or lower briefing in the heavier showers.
Shower activity should gradually diminish in coverage in the
evening as slightly drier air filters in from the north.

&&

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

$$

NEAR TERM...RSB
SHORT TERM....70
LONG TERM....JMS
AVIATION...RSB