128
FXUS64 KHUN 072011
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
311 PM CDT Tue May 7 2024

...New NEAR TERM, SHORT TERM...

.NEAR TERM...
(Tonight and Wednesday)
Issued at 311 PM CDT Tue May 7 2024

Upper level southwest flow with subtle shortwaves are expected
aloft over the Tennessee Valley this evening and overnight.
Meanwhile, a trailing cold front from a surface low over the Great
Lakes will slowly approach the Tennessee Valley overnight as
well. Overall, the environment is conducive for storm development
this evening with dewpoints in the 70s, along with instability
values over 2000 J/kg, bulk shear values between 20-30 knots, and
mid level lapse rates between 6.5-7.5 deg C/km. In addition, a low
level jet will be present tonight, but likely remain around 25
knots over our area. However, guidance suggests the LLJ will be
stronger to our north.

Over the past hour or so, light showers have streamed over
northern Alabama and southern middle Tennessee with only a few
flashes of lightning detected. If storms can get going, they have
the capability of becoming severe and producing damaging winds
and hail. Hi-Res models also indicate another round of showers and
storms tonight, perhaps beginning just before midnight, and
continuing into Wednesday morning. The big question is whether or
not these storms, which will move south of Tennessee this evening,
will make it far enough south into our local area. If they do,
confidence is low whether they will make it south of the Tennessee
River. CAMs solutions differ widely with what scenario will play
out. Ultimately, should storms enter our area, they have the
potential of producing damaging winds and hail. Make sure to have
multiple ways of receiving warning information tonight!

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.

&&

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

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...
(18Z TAFS)
Issued at 1258 PM CDT Tue May 7 2024

Unsettled weather will comprise the forecast through midweek.
Light showers have developed over the region this afternoon.
Anticipating low to medium (20-50%) chances of showers with a few
storms by mid-afternoon and into this evening. Some of these
storms may become severe, bringing the risk of damaging winds as
well as hail. A brief lull is then possible by mid-evening before
another round of showers and a few storms may develop and move
across the area later tonight (mainly north of the TN River). A
few of these storms could become severe with damaging winds and
hail the main threats. Low chances (20-30%) of showers/storms will
then persist Wednesday morning. Reduced CIGs to MVFR and possibly
to IFR are forecast late tonight through Wednesday morning as
well. South/southwest winds between 10-15 knots will continue
through this evening, with some wind gusts to around 20 knots this
afternoon. Winds are then expected to decrease to between 5-10
knots Wednesday morning.

&&

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

$$

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