406
FXUS64 KHUN 152239
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
539 PM CDT Tue Jul 15 2025

...New AVIATION...

.NEAR TERM...
(Tonight)
Issued at 252 PM CDT Tue Jul 15 2025

Despite a fairly buoyant airmass with MLCAPE values between
1500-2500 J/kg, showers and thunderstorms have struggled to
maintain any intensity and have been short lived so far this
afternoon. The main impact will continue to be the dangerous heat
as afternoon heat indices currently range from the mid 90s to
lower 100s. Will maintain very low chance PoPs between 10-20%
through the afternoon with the low chance of a thunderstorm
producing brief heavy rainfall and gusty winds. We will have to
monitor for dense fog once again late tonight into tomorrow
morning, but have no current plans to issue a dense fog advisory.
Otherwise, the previous discussion remains on track.

Previous discussion:
Although a few diurnally-initiated showers and thunderstorms will
be possible (especially in the higher terrain of northeast
AL/southern Middle TN), coverage of convective cells should be
higher both to our northwest (from the Ozarks into the central OH
Valley -- where the influence of the shortwave trough will be
greatest) and to our east (from the central FL Panhandle north-
northeastward into northern GA -- where a surface trough related
to the easterly wave will exist). Regardless of storm coverage,
the local thermodynamic environment will be characterized by
MLCAPE in the 2000-3000 J/kg range, DCAPE of 750-1000 J/kg and
PWAT in the 1.7-1.9" range. Thus, brief strong outflow wind gusts
(up to 40-50 MPH), frequent lightning and heavy rainfall will be
possible with stronger cells as they drift slowly east-
southeastward.

This evening, the surface trough to our east is predicted to
drift slowly west-northwestward and should reside across the
eastern portion of the CWFA by early Wednesday morning. A few
showers and thunderstorms will be possible throughout the night in
the vicinity of the trough, but mostly clear skies and dry
conditions are expected elsewhere. With calm winds and narrow
dewpoint depressions, patchy fog will also be possible in a few
locations around sunrise as temps fall into the l-m 70s.

&&

.SHORT TERM...
(Wednesday through Thursday night)
Issued at 1100 AM CDT Tue Jul 15 2025

During the period from Wednesday through Thursday night, the
western portion of the southeastern CONUS 500-mb ridge (discussed
above) will begin to weaken, with the configuration of the ridge
taking on a more zonal orientation from the Arklatex into the
southeastern Atlantic Coast (as it becomes conjoined with a
stronger subtropical high retrograding across the southwestern
North Atlantic). Although this suggests that there will be little
(if any) change in the general synoptic environment across our
forecast area through the duration of the short term period, the
presence of the surface trough (discussed above) should focus an
increase in the coverage of showers and thunderstorms across our
region beginning late tomorrow morning. With forecast soundings
indicating similar thermodynamic parameters in place tomorrow
(compared to today), storm impacts will be similar. However,
collapsing steering currents will result in even slower and more
erratic cell motions, perhaps increasing the risk for heavy
rainfall/minor flooding. In the event that early initiation of
showers/storms (and convective debris clouds) are not very
impactful, HI readings may reach 105-110F readings across the
valley. For that reason, a Heat Advisory has been issued for 10 AM
through 7 PM Wednesday.

The increasingly ill-defined surface trough is predicted to
progress further northwestward and through the region on Wednesday
night/early Thursday morning, as southerly flow strengthens in
the low-levels between a Bermuda high building into the
southeastern Atlantic Coast and a weak area of low pressure over
the north-central Gulf, and this may support a continuation of
scattered showers and thunderstorms for much of the night. The
modest increase in southerly flow in the boundary layer will
continue on Thursday/Thursday night, with precipitable water
values expected to rise above 2" during this timeframe. Although
this will support an increase in the coverage of afternoon
thunderstorms across southern portions of the central Gulf Coast
states, our main source of convective initiation may come late
Thursday afternoon or Thursday evening as outflow spreads
southeastward across western/Middle TN from frontal precipitation
across the Mid-MS/Lower-OH Valleys. With highs once again
predicted to reach the l-m 90s (and slightly higher dewpoints), a
Heat Advisory may be warranted on Thursday as well.

&&

.LONG TERM...
(Friday through Monday)
Issued at 1017 PM CDT Mon Jul 14 2025

Our attention in the extended will focus on the progress of
Invest 93L that will be moving westward over the northern Gulf
during the middle of this week. Some guidance indicates this
system may develop tropical characteristics before it veers into
the LA/MS/AL coastline during a Thursday night to Friday
timeframe. All this would mean for the Tennessee Valley will be
the potential for a gradual increase in PoPs Friday and
potentially into the upcoming weekend. How widespread this
activity will be will depend on the eventual track of this system,
but long range ensembles are honing on at least medium chances
for showers and thunderstorms. This would especially be true if
this feature begins to interact with a weak frontal boundary
attempting to push southeast from the Ohio/Mid-Mississippi Valley.
Given the deep tropical moisture that will be present across the
Deep South, locally heavy rainfall and potentially flooding would
be the primary concerns. Thus, the track of this system and how it
evolves is something we`ll need to watch in the coming days.
Given the added cloud cover and potentially higher rain chances,
heat impacts don`t appear to be as high during this late week
timeframe.

&&

.AVIATION...
(00Z TAFS)
Issued at 539 PM CDT Tue Jul 15 2025

VFR will be the prevailing flight category through the TAF period.
From 6-12Z, patchy fog is possible across the area, this was not
included in the TAF at this time due to low confidence. A TEMPO
group for fog may be added in the next TAF issuance.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory from 10 AM to 7 PM CDT Wednesday for ALZ001>007-
     016.

TN...None.
&&

$$

NEAR TERM...25
SHORT TERM....70
LONG TERM....AMP
AVIATION...RAD