929
FXUS64 KHUN 272344
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
644 PM CDT Fri Jun 27 2025

...New AVIATION...

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 347 PM CDT Fri Jun 27 2025

There have been no significant changes to forecast reasoning for
the near term period. Current radar data/satellite imagery/surface
observations suggest that a stable/rain-cooled airmass has
overspread the majority of the forecast area as of this writing,
with convective cells in progress along the periphery of this
airmass (i.e. across northeast AL) expected to either dissipate or
move eastward and out of the region by 22-23Z. Although a few
showers and storms may redevelop along the southern edge of the
outflow boundary (south of the TN River) early this evening, both
coverage and intensity should be notably less than what was
observed earlier today (due to the onset of the nocturnal cooling
cycle). After a temporary period of drier conditions late this
evening and early Saturday morning (when patchy fog may develop as
temps fall into the u60s-l70s), there is still some concern that
convection may redevelop across eastern portions of the CWFA prior
to sunrise as an upper air disturbance lifts northwestward (a
potential scenario discussed earlier this morning). Although this
activity should be sub-severe (if it indeed materializes),
lightning and locally heavy rainfall/flash flooding will remain a
concern.

Previous Discussion:
Thunderstorms began to rapidly develop between 14-15Z in the
vicinity of what appears to be a remnant outflow boundary/low-
level streamline confluence axis extending from Middle TN south-
southwestward into northeastern MS. With the uncontaminated storm
environment predicted to progressively destabilize throughout the
afternoon, we expect several outflow boundaries propagating away
from the initial cells to generate new convection, with additional
storms forming within terrain-induced circulations in the
vicinity of the Cumberland Plateau/Sand Mountain/Lookout Mountain.
Forecast soundings exhibit weak/unorganized flow throughout the
lower-middle troposphere, which will continue as the remnants of a
weak mid-level trough lift northwestward across GA. This will
result in erratic cell motions and an attendant risk for excessive
rainfall/flash flooding (with PWAT values in the 1.8-2" range).
Locally damaging downburst winds (up to 60 MPH) and frequent
lightning will also be concerns given MLCAPE of 2500-3500 J/kg and
DCAPE of 750-1250 J/kg. Due to the early onset of precipitation
and convective clouds, Heat Advisory criteria will likely not be
met in portions of the CWFA. However, in other locations where
temperatures reach the 88-92F range, heat indices may briefly
touch 105F. Thus, we will maintain the NPW in its current form and
let it expire on schedule at 0Z.

The general expectation is that convection will gradually
dissipate across the southeastern portion of the CWFA late this
afternoon/early this evening, as a more stable/rain-cooled airmass
begins to overspread the entire region. However, with a remnant
lobe of vorticity (related to the previously mentioned mid-level
trough) potentially pivoting northwestward into the region early
Saturday morning, we will need to keep an eye out for additional
convective development to our southeast that may spread
northwestward into the region prior to sunrise. Otherwise,
nocturnal convection should largely be tied to a subtle low-level
convergence axis extending from northeastern AR into the Lower OH
Valley (off the southwestern end of a cold front shifting
southeastward through the eastern Great Lakes). Finally, lows will
be in the u60s-l70s, with patchy fog possible in locations that
experience wetting rainfall.

&&

.SHORT TERM...
(Saturday through Sunday night)
Issued at 1126 AM CDT Fri Jun 27 2025

Latest short term model solutions suggest that the remnant mid-
level trough to our southeast will gradually decay across eastern
GA and adjacent portions of the Savannah Valley on
Saturday/Saturday night, as mid-level heights begin to rise across
the northwestern Gulf Coast (before a weak 500-mb ridge builds
into the region from the southwest on Sunday/Sunday night). This
configuration will maintain weak flow throughout the atmospheric
column, and in the absence of meaningful synoptic scale forcing
for ascent, we expect mainly diurnal convection in our region that
will largely be tied to mesoscale outflow/differential heating
boundaries (as well we terrain-induced circulations across the
eastern portion of the forecast area). With precipitable water
values predicted to remain solidly in the 1.8-2" range,
slow/erratic storm motions will yield a risk for flash flooding on
a daily basis. Fortunately, both CAPE and DCAPE values may both
slowly decline over the course of the weekend as the mid-levels
moisten (and lapse rates weaken), and this may reduce the risk for
severe-caliber downburst winds (although gusty outflow winds of
40-50 MPH can be expected each day). Highs will be in the
u80-l90s, with lows in the u60s-l70s and with heat index readings
in the 95-100F range we do not foresee the need for expansion of
the Heat Advisory at this point.

&&

.LONG TERM...
(Monday through Thursday)
Issued at 1042 PM CDT Thu Jun 26 2025

Heading into next week the upper level pattern begins to shift as
a trough digs down across the Upper Midwest. This will push a
cold front south across the Ohio and Tennessee River Valleys. This
boundary will slowly push southward across the local forecast
area on Monday into Tuesday bringing high chances for showers and
storms. At this time severe storms are not anticipated given the
weak shear, but with forecast instability expected to rise between
1500-2000 J/kg each afternoon a strong storm or two is possible.
The front will slowly shift south of the forecast area by the
middle of next week bringing drier and less humid conditions to
the Tennessee Valley. Unfortunately, as is typical with summertime
weather in the Southeast, there continues to be low to medium
chances for diurnally driven showers and storms both Wednesday and
Thursday.

&&

.AVIATION...
(00Z TAFS)
Issued at 644 PM CDT Fri Jun 27 2025

Shower and thunderstorm activity have dissipated across much of
northern AL. Not expecting storms to move back into either
terminal before sunset, with activity well to the east of KHSV
should dissipate with the loss of daytime heating. Heavy rainfall
near the KMSL terminal today and light winds/clearing later in the
evening should lead to some fog formation near that terminal.
This fog could be dense between 28/8Z and 28/12Z. KHSV did not see
much rainfall today so fog development is much more uncertain
there. MVFR VSBYS reductions were left in a tempo group at KHSV
between 28/08Z and 28/12Z for patchy fog development though. At
both terminals, VFR conditions should return by 15Z. A PROB30
group was included at both terminals between 28/21 and 28/24Z for
possible afternoon -TSRA development. During this period, some
MVFR or lower conditions could affect either terminal.

&&

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

$$

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