805
FXUS64 KHUN 080548
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1248 AM CDT Wed May 8 2024

...New AVIATION...

.NEAR TERM...
(Tonight)
Issued at 919 PM CDT Tue May 7 2024

The storms that rumbled across portions of north Alabama and
southern middle Tennessee have shifted east into Georgia -- with
only a few light showers lingering across northeast Alabama.
Observational data and the latest guidance supports more
sufficient surface-based instability with SBCAPE values between
1000-2000 J/kg coupled with bulk shear values of 30-40 kts for the
remainder of the overnight period. Guidance continues to support
convection developing along a remnant boundary across western and
middle Tennessee after Midnight which will drift ESE toward the
area -- approaching northern portions of the area early Wednesday
morning. The environment will support damaging wind and hail with
the strongest cells (if they can make it into southern middle
Tennessee and northern Alabama). Additionally, a very low
(isolated) tornado threat with the strongest convection that can
be sustained. Again, confidence remains low on whether this
activity will make it into the area and exactly how far south this
they will make it. Still, given the aforementioned environment, it
is important for folks to have multiple ways to get warnings
overnight in case a warning is issued for your location.

&&

.SHORT TERM...
(Wednesday through Thursday Night)
Issued at 311 PM CDT Tue May 7 2024

For the rest of the day on Wednesday, low to medium (20-50%)
chances of showers and storms are mostly forecast; however, not
anticipating these to be severe at this time. For temperatures, it
will be fairly warm tonight due to elevated moisture, with lows
only dropping into the mid 60s to lower 70s. Highs Wednesday are
then forecast to top out in the 80s.

The "main event" in terms of severe weather will come in the form
of a mesoscale convective system (MCS) traversing the Tennessee
Valley Wednesday night into Thursday morning. Upper level
southwest flow will continue, but more potent upper shortwaves are
shown by models to ripple over the region Wednesday night into
early Thursday. In addition, another low pressure system looks to
develop and track over the Midwest by Wednesday evening,
progressing east into the Ohio Valley by Thursday morning. Model
instability will be lower overnight; but, even so, values are
shown by guidance to be around 2000 J/kg. Bulk shear values range
between 30-50 knots as well, with a stronger LLJ to between 35-40
knots over the region. Midlevel lapse rates are also higher,
between 7-8 deg C/km along with 0-1 km SRH between 200-250 m2/s2.

Therefore, the ingredients are in place for all modes of severe
weather Wednesday night into Thursday morning: damaging winds,
hail, and embedded tornadoes. Models have also been fairly
consistent with the timing of this MCS, with it reaching
northwestern Alabama around midnight and moving southeast over the
local area during the overnight hours, exiting around 8AM. The
Storm Prediction Center has the majority of our area in a Slight
Risk (level 2/5) of severe weather, with portions of our southern
middle Tennessee counties in an Enhanced Risk (level 3/5). Again,
please make sure to have multiple ways to receive warnings,
especially ones that will wake you up in the middle of the night!

Another concern is the potential for localized flooding,
especially where storms train over the same locations repeatedly.
At this point, our forecast storm total rainfall ranges from 1-2
inches, with locally higher amounts possible. Turn around, don`t
drown if you encounter flooded roads - find an alternate route!

Once the MCS moves south of the area Thursday morning, residual
chances (low to medium; 30-50%) of showers and some storms remain
possible through Thursday evening.

&&

.LONG TERM...
(Friday through Monday)
Issued at 427 AM CDT Tue May 7 2024

Prevailing NW flow aloft will exist across the region for much of
the extended period, allowing a cooler and drier Canadian airmass
to be advected deep into the southeastern CONUS. Highs will be in
the 70s, with lows in the 50s, and although conditions will
remain dry for most of the region, at least a couple of well-
defined vorticity lobes will track southeastward across the TN
Valley on Friday/Saturday, warranting a very low POP for light
showers.

&&

.AVIATION...
(06Z TAFS)
Issued at 1248 AM CDT Wed May 8 2024

VFR conditions are currently observed at the HSV/MSL terminals,
but there are indications that low stratus clouds will develop
within the very moist boundary layer, providing MVFR cigs arnd
1500 ft AGL btwn 9-15Z. As the low stratus layer disperses later
this morning, a rapidly destabilizing airmass will support the
development of sct-bkn Cu, with the risk for a few warm sector
TSRA increasing in the 21-03Z timeframe. Although probabilities
for more a more widespread coverage of storms will increase with
time as we approach the end of the TAF period, confidence is not
high enough to introduce anything more than an additional PROB30
group attm. Prevailing sfc flow will remain from the SSW, with
sustained speeds of 5-10 knots (and gusts of 15-20 knots this
aftn).

&&

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

&&

$$

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