324
FXUS64 KHUN 071758 AAA
AFDHUN

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
1258 PM CDT Tue May 7 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 958 AM CDT Tue May 7 2024

Low clouds across the area will become more cellular over the next
couple hours, allowing more significant heating to take place. A
shortwave impulse over AR/LA along with moisture transport axis
along the MS valley shifting east will result in shower and
thunderstorm development during peak heating this afternoon. The
thunderstorms will enter northwest AL after 12-1 pm, and shift
east with time this afternoon. The 12Z BMX RAOB indicated a
moderate capping inversion around 780mb, but temperatures warming
into the lower to middle 80s along with the shortwave should erode
that fairly easily, especially with dew points around 70. SBCAPE
values of 2000-2500 j/KG and 6km bulk shear values of 30-40kt will
be sufficient for supercells capable of large hail and isolated
damaging wind. We may need to increase PoPs later, but for now
stayed somewhat conservative at this point based on CAMs from 00Z.
The forecast for tonight looks good, and will have to watch
closely for an east-west orientation of thunderstorms late tonight
that could create some excessive rain issues.

&&

.SHORT TERM...
(Tonight through Thursday night)
Issued at 427 AM CDT Tue May 7 2024

Afternoon storms may continue for a couple of hours after 00Z
across the southeastern portion of the forecast area, before
gradually diminishing in coverage/intensity with the onset of the
diurnal cooling cycle. However, to our northwest, additional
convection may develop late this afternoon or early this evening
in the vicinity of another surface trough extending from the
Central OH Valley southwestward into eastern AR/western TN. This
activity may tend to expand in coverage as it spreads
southeastward into Middle TN early Wednesday morning, perhaps
reaching the northern portion of our forecast area between 9-12Z.
During this same timeframe, additional storms may develop along
and north of a surface trough extending southeastward into central
MS/AL from an area of low pressure tracking eastward across
northern OK, and POPs have been increased for the entire region
between 6-12Z. Although instability will weaken to some extent
overnight, the environment will continue to feature steep lapse
rates and strong vertical shear, thus warranting concern for a few
severe storms through early Wednesday morning.

It still appears as if any convection in our forecast area around
12Z Wednesday will spread northeastward and out of the region by
15Z, as the surface trough across central AL/MS begins to lift
northward before eventually eventually transitioning into an
effective warm front attached to the synoptic cyclone advancing
northeastward into the Mid-MS Valley. Widespread severe
thunderstorms are anticipated along and immediately north of this
warm front Wednesday afternoon, which should extend from the
Ozarks east-southeastward into the southern Appalachians. However,
our region will likely remain warm, dry and capped for much of
the day. That said, a few models suggest that isolated warm sector
thunderstorms (likely supercellular in structure) may develop to
our southwest very late Wednesday afternoon and shift
northeastward early Wednesday evening, posing a risk for severe
wind/hail.

Of more concern for our region is development of thunderstorms
along the cyclones trailing cold front, which should extend from
the low southwestward into northeastern TX late Wednesday
afternoon. This activity will likely grow upscale in an intense
MCS over the course of the evening, that would spread
southeastward through our region early Thursday morning (6-12Z
timeframe). Although a similar background kinematic and
thermodynamic environment will exist ahead of the MCS, there are
indications that a subtle increase in the low-level jet can be
expected ahead of this rather large convective complex, and for
this reason, a minor increase in the risk for tornadoes is
expected overnight (in addition to large hail and damaging winds).

Current expectations are that the MCS should be spreading
southeastward and away from the region around 12Z Thursday, with
trailing stratiform rain expected to end from NW-to-SE beginning
early Thursday afternoon. Although redevelopment of a few showers
and thunderstorms will be possible along the actual cold front
Thursday afternoon, widespread overturning in the wake of the
morning MCS should limit concern for severe weather. The cold
front is predicted to be shifting southeastward and out of the
region early Thursday evening, but with a separate complex of
convection expected to spread eastward along the central Gulf
Coast Thursday night, we have maintained a low POP for light rain
on the northern fringe of this system early Friday morning.

&&

.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...17
SHORT TERM....70
LONG TERM....70
AVIATION...26