259
FXUS64 KHUN 171736
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1236 PM CDT Sat Aug 17 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 930 AM CDT Sat Aug 17 2024

A sfc low continuing eastward through the Great Lakes has brought
a very slow moving cold front through the OH River Valley into
the lower Plains. Ahead of this, several clusters of storms are
forecast to form with the assistance of diurnal heating this
afternoon. Any storms that form will be capable of becoming strong
to severe, with threats of gusty to damaging winds, small hail, and
frequent lightning being the main threats. `Inverted V` sounding
profiles with sufficient dry air aloft hint at the potential for
downbursts this afternoon with DCAPE values over 1000 J/kg and low
level lapse rates around 8-9 C/km. Shear should remain relatively
limited, peaking around 25 kts and limiting organized convection
as well as the tornado threat. Our flooding threat will be low as
well, with PWATS around 1.4-1.6" which is the median value within
sounding climatology per BMX. However, with any downbursts,
ponding of water in areas of poor drainage (such as roadways) is
likely. Current timing of these storms are between 1 PM CDT and 8
PM CDT, however, there is a low chance these linger past 8 PM CDT
as they move southeast through the area.

Our other large concern today is the heat as high temperatures
reach the mid to upper 90s with heat indices in the upper 90s to
low 100s. A Heat Advisory is in effect for northwest AL (Marshall,
Cullman, and Madison counties westward) beginning at 1 PM CDT and
continuing through 7 PM CDT. In areas that do not see rain, heat
will be a higher threat due to lack for relief from cloud cover.
We encourage everyone to remain hydrated and take frequent breaks
if outdoors.

&&

.SHORT TERM...
(Tonight through Monday night)
Issued at 427 AM CDT Sat Aug 17 2024

Though this boundary will move southeast into southern/central
Alabama early this evening, pushing the higher shower/thunderstorm
chances into those locations, an approaching secondary cold front
will likely keep isolated to scattered showers and thunderstorms
in the forecast Saturday night into Sunday. Some of these could be
strong to marginally severe. Main threats with these storms would
likely be damaging winds. Despite a good deal of sunshine expected,
cold air advection should keep highs from climbing much above the
mid 80s to lower 90s on Tuesday. Somewhat drier air will be in
place though near and behind this final cold front as well
allowing dewpoints to drop into the mid 60s to lower 70s Sunday
afternoon.

Really nice weather is on tap Monday and Tuesday with highs in the
mid to upper 80s both days and lows in the 60s (lower 60s when you
wake up on Tuesday).

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 427 AM CDT Sat Aug 17 2024

Latest extended range guidance suggests that an amplified longwave
trough will encompass much of eastern North America on
Tuesday/Wednesday, maintaining moderately strong NNW flow aloft
across the TN Valley. In the low-levels, light-moderate northerly
winds will persist to the south of a surface high across southern
Ontario and to the north of a weak frontal wave that is predicted to
retrograde west-southwestward from the southeastern Atlantic Coast
into the western FL Panhandle/south AL vicinity by Thursday morning.
Dewpoints will generally remain in the m-u 50s, with highs on both
Tuesday/Wednesday in the m-u 80s (u70s-l80s in elevated terrain).
Overnight lows will be in the m-u 50s Wednesday morning, and in the
u50s-m60s Thursday morning, as a surface trough extending northward
from the frontal wave will cross the region during this timeframe
resulting in a gradual increase in easterly flow. During the period
from Thursday-Friday, the northern portion of the longwave trough
will advance northeastward off the coast of New England, as a weak
cutoff upper low becomes established over the northwestern Gulf of
Mexico. A SE low-level flow regime will result in slightly warmer
afternoon temps in the u80s-l90s, but will also continue to advect
dry air into the region from the remnant surface high to our
northeast, keeping heat indices near ambient air temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1236 PM CDT Sat Aug 17 2024

VFR conditions are forecast through the TAF period at both KMSL
and KHSV. This afternoon into this evening, VCTS are possible at
both sites. If thunderstorms move directly over KMSL or KHSV,
amendments will be needed to account for lowered
visibilities/ceilings and subsequent IFR to MVFR conditions.
However, confidence is too low in coverage at this point to
officially include thunderstorms as a prevailing group. Overnight
into Sunday morning, there is a low chance of fog formation in
areas that receive rainfall. If this occurs, IFR to MVFR
conditions will be possible due to lowered visibilities.
Confidence is too low to officially include fog in the TAF at this
time.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory until 7 PM CDT this evening for ALZ001>008-016.

TN...None.
&&

$$

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