691
FXUS64 KHUN 311854
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
154 PM CDT Thu Jul 31 2025

...New NEAR TERM...

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 154 PM CDT Thu Jul 31 2025

There have been no significant changes to the near term forecast
since the update earlier this morning, with development of showers
and thunderstorms expected to continue throughout the afternoon.
Although convection is currently initiating near a prefrontal
surface trough across northwest AL, additional formation is
anticipated in the vicinity of several small outflow boundaries
across the eastern half of the CWFA, as well. Individual cells
will travel slowly east-southeastward before dissipating around
sunset, but with some risk for frontal convection to spread
southeastward into the region this evening, we will retain a low
(15-25%) POP through 6Z. As we mentioned earlier, the main impacts
from the stronger storms will be brief downburst winds (up to
50-60 MPH), frequent lightning and locally heavy rainfall. With
most valley locations expected to at least briefly achieve a HI of
105F prior to the onset of convective impacts, we will leave the
Heat Advisory intact at the current time.

Previous Discussion:
In the mid/upper-levels, a broad weakness in the subtropical
ridge currently extends from the western Gulf northeastward into
northern portions of MS/AL (between two distinct highs centered
across the FL Peninsula and northern Mexico). At the surface, a
well-defined cold front stretches from the Red River Valley
northeastward through the Mid-South/Upper OH Valley and into the
northern Mid-Atlantic states, with a prefrontal surface
trough/wind shift axis to NNW expected to spread gradually
southeastward into the northwestern portion of our forecast area
this afternoon.

Present indications are that showers and thunderstorms today will
be most concentrated in the vicinity of the cold front to our
northwest, although some convection will begin to develop between
16-18Z as the prefrontal trough enters our region and begins to
interact with the preexisting warm/moist airmass. Although an
abundant coverage of mid/high-level stratiform clouds within the
weakness in the subtropical ridge may tend to limit buoyancy and
delay convective development by a few hours, it appears as if
storm coverage will be highest across the southeastern corner of
the CWFA, as cells should spread east-southeastward with time.
Presuming that sufficient breaks in the cloud cover aloft occur
this afternoon to permit temps to reach the l-m 90s, dewpoints in
the mid 70s will support CAPE of 2000-2500 J/kg and an attendant
threat for downburst winds up to 50-60 MPH with the most intense
cells. Otherwise, locally heavy rainfall and flooding will also be
a concern given the combination of PWAT values in the 1.9-2.1"
range and weak steering currents. Due to the temperatures and
dewpoints mentioned earlier, HI will likely reach the 105-109F
range for many locations in the lower terrain, and a Heat Advisory
remains in effect through 9 PM.

Although convection related to the prefrontal trough will exhibit
a diurnal weakening/dissipation trend with sunset this evening,
we will need to keep an eye out to the northwest, as thunderstorms
occurring in the vicinity of the cold front may persist for much
of the evening. As an area of low pressure (which will evolve
across eastern VA over the course of the day today) begins to
shift northeastward and off the Mid-Atlantic Coast, the front will
make steady southeastward progress overnight, and this could
potentially result in a continuation of at least scattered
thunderstorms in our forecast area this evening. With the cold
front not expected to reach the local region until Friday, it will
be another warm/muggy night, with development of low stratus
clouds expected prior to sunrise as temps fall into the l-m 70s.

&&

.SHORT TERM...
(Friday through Saturday night)
Issued at 1111 AM CDT Thu Jul 31 2025

Latest model guidance suggests that a cold front will track
slowly southward across the TN Valley during the day on Friday in
response to amplification of a mid/upper-level longwave trough
across eastern Canada. This will allow the leading/modified edge
of a cooler/drier continental airmass (centered over the Upper MS
Valley) to be advected southward into the region, with dewpoints
expected to fall from the mid 70s into the u60s-l70s north of the
TN River by late afternoon. Low-level forcing for ascent along the
cold front will result in another high coverage of showers and
thunderstorms from late tomorrow morning through the afternoon,
with the greatest spatial concentration of convection expected to
occur along an south of the TN River. Aside from a minor increase
in WNW flow aloft within the southern portion of the amplifying
longwave trough, there will be little change in the kinematic
environment tomorrow, and with thermodynamic parameters expected
to be similar to today, storm impacts will remain unchanged.

Thunderstorms will progress southward in conjunction with the
cold front Friday afternoon/evening, likely exiting our region
shortly after sunset (if not sooner). Light NNE winds in the
boundary layer will continue to advect drier air into the region
throughout the night, with dewpoints ranging from the l60s (N) to
u60s (S) and lows by Saturday morning falling into the 65-70F
range.

During the period from Saturday-Saturday night, a weak frontal
wave is predicted to develop across southern GA/northern FL before
retrograding slowly westward along the central Gulf Coast. As
this occurs, a surface trough extending northward from the low
will track northwestward across our region, with a modest increase
in E-SE flow in the wake of the trough allowing dewpoints to
climb back up into the u60s-l70s. This will yield an increase in
showers/thunderstorms across the southeastern portion of the
forecast area Saturday afternoon, with this regime expected to
expand northwestward to encompass the entire region Saturday
evening. The combination of cooler surface temperatures and weaker
low/mid-level lapse rates will contribute to lower CAPE, with
general thunderstorm activity expected at this time.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 958 PM CDT Wed Jul 30 2025

An upper trough with a few shortwaves moving along it will
persist over the eastern US through the long term period. In fact,
guidance indicates that the trough will further amplify by
Wednesday and become positively tilted. At the surface, an
inverted trough feature will set up by late weekend, with a
stalled front to the south near the Gulf coast. This front will
meander over the coast for a couple of days then possibly shift
back north on Wednesday as a warm front. How far north this front
gets will be something we`ll need to keep an eye on. Moisture
levels increase through midweek, with model PWATs increasing from
1.3-1.4 inches Sunday and Monday to 1.6-1.8 Tuesday and Wednesday.
Overall, daily chances of showers and storms will be the theme as
we head into the first week of school for many, peaking during
the afternoon and evening hours. Confidence in any severe weather
is low due to bulk shear below 30 knots each day. Although, as
temperatures increase from the lower to mid 80s on Sunday into the
upper 80s to around 90 degrees by Wednesday, the better
instability may be realized Tuesday and Wednesday afternoons
compared with earlier in the week. Thus, with better moisture and
instability, a few stronger storms may be possible Tuesday and
especially Wednesday during the afternoon and evening hours that
could bring heavy downpours, frequent lightning, and some gusty
winds. Remember, when thunder roars, go indoors!

&&

.AVIATION...
(18Z TAFS)
Issued at 1252 PM CDT Thu Jul 31 2025

Scattered TSRA have begun to develop across portions of northern
AL/southern TN where breaks in the early morning mid/high-level
cloud canopy have enabled stronger destabilization of the boundary
layer. This activity will spread east-southeastward in
conjunction with a prefrontal trough, and should weaken/dissipate
around or shortly after sunset. However, until that point, we have
included a TEMPO for MVFR conds at both terminals from 18-22Z.
Although additional showers and storms (related to a cold front
approaching the region from the NW) may impact portions of the
forecast area this evening (until 5-6Z), uncertainty in storm
coverage is too high to include additional PROB30 groups in the
TAFs attm. As the front begins to sag southward into the region,
low stratus clouds are likely to develop as moisture pools ahead
of the boundary, with a period of MVFR cigs anticipated btwn
10-14Z. Convection will likely begin to redevelop invof the cold
front by 16-18Z Friday, but until the location of the front can be
determined, we will refrain from mentioning this in the forecast.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...Heat Advisory until 9 PM CDT this evening for ALZ001>010-016.

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

&&

$$

NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...26
AVIATION...70/DD