136
FXUS64 KHUN 202313
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
513 PM CST Thu Nov 20 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 1119 AM CST Thu Nov 20 2025

 - Rain and embedded thunderstorms will impact much of the region
   this afternoon, but should be exiting to the northeast early
   this evening. Lightning and brief, locally heavy rainfall will
   be the main concerns.

 - Additional showers and a few thunderstorms are expected on
   Friday and Friday night, with perhaps the greatest coverage of
   precipitation (and risk for a few strong storms) coming during
   the overnight period.

 - After lingering showers/storms end late Saturday morning, dry
   conditions are expected through Monday. However, we will be
   watching another strong storm system that could impact the
   region Monday night and Tuesday.

&&

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 150 PM CST Thu Nov 20 2025

There have been no significant changes to near term forecast
reasoning since the update earlier this morning, with the primary
feature of interest a large band of rain and embedded
thunderstorms that will continue to progress eastward at 30-35 MPH
this afternoon. Although south of the effective warm front,
SBCAPE has thus far been limited by widespread stratus clouds, but
with boundary layer temperatures climbing into the l-m 70s,
values are now approaching 600-800 J/kg to the east of the
precipitation shield. This along with steady improvement in deep-
layer shear (currently 45-50 kts per SPC mesoanalysis data) may
still support an occasional wind gust of 30-40 MPH with any deeper
updrafts (capable of producing lightning). It still appears as if
this precipitation regime will quickly exit our region to the
northeast between 23-2Z, with only a few remaining showers
(focused along and north of the AL-TN border) ending later this
evening. Due to a light SSW wind and overcast high-level clouds,
overnight lows will be in the u50s-l60s.

Previous Discussion:
In the mid/upper-levels, a southern stream shortwave trough
(initially across the southwestern CONUS/northwestern Mexico) will
accelerate northeastward into the central High Plains by 12Z
Friday as it travels along the northern rim of a subtropical ridge
centered across the southern Gulf. Although the trough is
generally predicted to weaken with time, it will acquire a sharp
negative tilt by the end of the period, which will support further
development of a weak area of low pressure as it lifts
northeastward from the southern High Plains into southeastern KS.
Extending to the east of the developing low, a warm front will
shift slowly northward across TN today, with light SSW flow in the
low-levels across our region sustaining a very moist boundary
layer featuring dewpoints in the l-m 60s. Present indications are
that widespread rain and embedded thunderstorms (currently
extending from southern AR northeastward into western TN) will
continue to spread northeastward and should impact much of the
local area this afternoon. Even with this regime located south of
the warm front, widespread low stratus clouds (originating from
gradual lifting of the antecedent ground fog layer) will keep CAPE
confined to 200-400 J/kg at most, with occasional lightning and
pockets of locally heavy rainfall the primary concerns. Presuming
that cloud bases gradually lift this afternoon and some scattering
occurs, highs may reach the mid 70s in a few a locations, but
this may be a bit optimistic.

Guidance from the most recent suite of CAMs suggests that rain
and embedded weak convection will be exiting the northeastern
corner of our CWFA early this evening, and with forecast soundings
suggestive of drying in the low/mid-levels after Midnight, we
will maintain very low POPs (5-10%) from 6-12Z Friday. Although
the elevated advection of drier air into the region will
contribute to less cloud cover, a broken-overcast layer of
cirrostratus clouds coupled with a light SSW breeze should reduce
coverage and density of fog (compared to this morning) as temps
fall into the u50s-l60s.

&&

.SHORT TERM...
(Friday through Saturday night)
Issued at 1119 AM CST Thu Nov 20 2025

A 500-mb trough (initially across the central High Plains) will
become increasingly sheared during the day tomorrow as tracks
eastward into the Lower-OH Valley and enters a region of
increasingly confluent flow aloft. As this occurs, a gradually
weakening area of surface low pressure will also shift eastward
into Lower OH Valley, with widespread rain and embedded
thunderstorms expected to lift northeastward from the Mid-South
region into the Upper-OH Valley throughout the day (in conjunction
with the synoptic warm front). Although this regime will bypass
our forecast area to the north, a separate region of showers and
thunderstorms (related to a strengthening southwesterly low-level
jet) should begin to evolve from the Lower-MS Valley into
northern/central MS prior to 12Z and expand into northern/central
portions of AL throughout the day. Although there is still
uncertainty regarding how far northeast this precipitation regime
will expand into our region, it will likely represent the main
source of rainfall in our region. With mid- level westerly flow of
50-60 knots in place across the region, deep-layer shear will be
conducive for organized convection. However, due to early
development of low stratus clouds (shortly after 12Z) and poor
lapse rates aloft, CAPE will remain limited to less than 250 J/kg,
and for this reason any thunderstorms should remain well below
strong-severe thresholds.

Models indicate that the Lower-OH Valley surface low will track
quickly eastward and off the Mid-Atlantic Coast by 12Z Saturday,
with a separate axis of showers and thunderstorms likely to
develop along a trailing cold front (across western TN) by late
Friday evening. Current thinking is that this activity will
progress southeastward through our CWFA early Saturday morning,
and may actually offer the best opportunity for a few strong
thunderstorms (in spite of the unfavorable time of day) as lapse
rates aloft will slowly improve in the presence of favorable deep-
layer shear. The cold front will advance southeastward throughout
the day on Saturday, with increasing NW winds in its wake
allowing dewpoints to fall into the mid 50s by late afternoon.
However, lingering low stratus clouds and perhaps a few pockets of
light rain or sprinkles will be possible throughout the day. By
Saturday evening, surface flow will veer to NNE as a low-level
ridge develops eastward into the southern/central Appalachians,
and clearing skies will promote cooler overnight lows in the l-m
40s.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 914 PM CST Wed Nov 19 2025

The long term forecast will be focused on the passage of a
surface cyclone and associated cold front on Tuesday. Through the
weekend and into the beginning of the work week, A mid level cut
off low will deepen and drop along the pacific coast before
progressing northeast through the CONUS. Ahead of its arrival, we
will find ourself between troughing to our SE and ridging to our
north. Unfortunately the two competing regimes will lead to little
changes in airmass in place meaning more days of partly to mostly
overcast conditions, low (10-30%) rain chances, highs in the 60s
and 70s and muggy dewpoints in the 50s and 60s through the start
of the work week.

Mid range models are in good agreement in bringing the front into
the TN Valley on Tuesday however still lack agreement regarding
the finer thermodynamic details and the evolution of surface
cyclone once it reaches the eastern CONUS. A few trends are
becoming apparent in the models that will make this system worth
watching for severe weather potential. First, we will maintain a
very moist boundary layer leading up to the passage of the front.
Additionally, the synoptic scale of the front will favor the
presence of sufficient bulk shear. With these two parameters
present, it won`t take much instability or forcing to support some
stronger storms within the larger area of rain. For now, stuck
with blended guidance bringing in 50-60% rain and thunder chances
with the front on Tuesday morning with 20-30% rain chances
lingering behind the front through Wednesday.

&&

.AVIATION...
(00Z TAFS)
Issued at 513 PM CST Thu Nov 20 2025

Area of showers from earlier this afternoon has pushed off to the
northeast into GA and E. TN. In its wake, low level clouds remain
across N. AL, but are still VFR. The clouds will linger until
morning before some low level clouds push in from the west
resulting in MVFR conditions. Expect showers and perhaps a
thunderstorm to reach NW AL around lunchtime tomorrow and then
push east and linger through the end of the TAF period. For now,
did not include thunder, but it will be something to keep an eye
on for future updates.

&&

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

$$

NEAR TERM...70
SHORT TERM....70
LONG TERM....RAD
AVIATION...GH