959
FXUS64 KHUN 291109
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
609 AM CDT Fri Aug 29 2025

...New AVIATION...

.NEAR TERM...
(Today)
Issued at 424 AM CDT Fri Aug 29 2025

Calm winds and clear skies are in place across southern middle
Tennessee and northern Alabama at this hour. Though drier air
continues to move slowly south behind a departed front to our
south, quickly falling temperatures are allowing for saturation in
the boundary layer over the past hour. This has lead to some
patchy fog forming in typical valley locations of NE Alabama and
southern middle Tennessee and also in NW Alabama near the
Tennessee River.

Models do show slightly drier air continuing to advect southwest
into the area through daybreak. However, the clear skies and
quickly falling temperatures will likely allow fog to increase in
coverage through 7 or 8 AM before dissipating. Not expecting
widespread dense fog at this time, but some visibility drops to
around 1 mile are possible in fog prone locations. Based on
current temperatures (54 to 60 degrees), lowered low temperatures
slightly into the lower 50s east of the I-65 corridor.

&&

.SHORT TERM...
(Friday night through Sunday night)
Issued at 1025 PM CDT Thu Aug 28 2025

Latest model guidance suggests that a subtle area of low pressure
(across southern MS at the beginning of the period) will slowly
track southeastward into the central/southern FL Peninsula by 0Z
Monday, before shifting eastward and offshore Sunday night. This
will lead to a continuation of light NE winds across the region
from Friday night-Saturday night, as we will be embedded within
the gradient between the low to our southeast and a broad area of
high pressure centered across the eastern Great Lakes. With NW
flow aloft of 15-25 knots maintaining a dry airmass in the
mid/upper-levels, dry conditions will prevail for most of the
forecast area. However, with an axis of rain and thunderstorms
(related to the surface low`s remnant warm front) expected to be
positioned to our southeast, a few sprinkles of rain could occur
at times across our southeastern counties. In spite of light NE
winds in the boundary layer, southward advection of the Canadian
airmass to our north will be weak across our region, and dewpoints
will slowly begin to creep upward leading to overnight lows in
the lower 60s Saturday/Sunday mornings. Highs on Saturday will
also increase a couple of degrees, but should remain in the m-u
80s for most of the lower elevation locations.

As the Canadian surface high to our north begins to spread
northeastward into New England/southern Quebec on Sunday and
Sunday night, cold air damming in the lee of the southern
Appalachians will send a backdoor cold front west-northwestward
into our region at some point late in the short term period.
Although subtle convergence in the vicinity of this boundary
should be sufficient for the generation of weak convection as PWAT
values rise back into the 1.3-1.5" range, CAPE will remain rather
low through 12Z Monday. Thus, we will advertise a low chance for
showers in the eastern portion of the CWFA Sunday afternoon and a
low chance region-wide Sunday night/Monday morning. Highs on
Sunday will be similar to those on Saturday, with lows returning
to the mid 60s in some locations Monday morning.

&&

.LONG TERM...
(Monday through Thursday)
Issued at 1025 PM CDT Thu Aug 28 2025

Extended range forecast data indicates that a slow-moving
backdoor cold front will be lifting west-northweatward across the
TN Valley on Monday, and could contribute to a higher coverage of
showers and thunderstorms across mainly the northern portion of
the forecast area (especially during the afternoon hours).
However, during the timeframe from Monday night-Tuesday night, the
coverage of convection is expected to increase region-wide, as a
south-southwesterly low-level jet will become established in
advance of a low-amplitude 500-mb wave dropping southeastward from
the northern Plains into the Mid-MS Valley (within the flow
around an amplifying northern stream trough digging south-
southeastward across central Canada). The southeastward-advancing
wave may lead to development of a surface trough across the Lower
MS Valley, which could ultimately interact with the remnants of
the backdoor cold front, leading to an increase in showers and
thunderstorms. Although richer moisture/higher CAPE may be
confined to our south, instability will be sufficient for
thunderstorms and locally heavy rain will be possible.

Rain and thunderstorms will begin to diminish in coverage from
W-to-E at some point Wednesday/Wednesday night as the mid-level
wave ejects northeastward into the Upper OH Valley. However, as a
deepening surface low (related to the northern stream trough)
begins to shift eastward across the northern Great Lakes/southern
Ontario, a stronger cold front will sweep southeastward into the
TN Valley on Thursday, potentially resulting in another round of
showers and thunderstorms (if moisture/instability are still
present). Should this occur, mid-level westerly flow of 30-40
knots may support a few stronger and more organized thunderstorms
during this period. Highs from Monday-Thursday will fall back into
the u70s-l80s due to clouds and precipitation, with lows
remaining in the l-m 60s.

&&

.AVIATION...
(12Z TAFS)
Issued at 606 AM CDT Fri Aug 29 2025

Some VSBY restrictions to around 2SM could still occur at KMSL
through 13Z. Then expect VFR conditions to return. Winds will
remain easterly around 5 knots or less this afternoon. Some patchy
fog may be possible late tonight at the terminals, but left out
for now.

&&

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

$$

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