397
FXUS64 KHUN 070927
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
427 AM CDT Tue May 7 2024

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

.NEAR TERM...
(Today)
Issued at 427 AM CDT Tue May 7 2024

A mid-level ridge translating eastward across the TN Valley early
this morning has resulted in dry conditions throughout the local
region. Well to our northwest, an extensive QLCS will continue to
spread eastward across the Upper/Mid-MS Valley by 12Z, as a
dryline surges eastward ahead of a deepening cyclone over the
northern Plains. Strengthening SSW flow in the low-levels (ahead
of this feature) has led to a warm night, with with temps
currently in the u60s-l70s for all but the sheltered valleys in
northeast AL/southern TN, and this will subsequently result in
another warm day featuring highs in the mid 80s.

Latest guidance from the CAMs suggests that scattered
thunderstorms will develop by mid-day in the vicinity of a weak
outflow boundary drifting southeastward off the southern edge of
the broader QLCS (that will bypass our region to the north).
Present indications are that this boundary will extend from the
Arklamiss northeastward into the TN Valley, and a medium POP has
been placed in the grids (focused across the northwestern half of
the CWFA) to indicated the presence of a mid-level inversion in
forecast soundings and scattered nature of storm coverage. With
mid-level WSW flow expected to increase into the 40-45 knot range
over the course of the day as the ridge shifts further eastward, a
25-35 knot SW low-level jet and CAPE in the 2500-3000 J/kg range
will favor supercellular storm structures with stronger updrafts
that can overcome the inversion, with large hail, damaging winds
and frequent lightning the primary concerns.

&&

.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...
(06Z TAFS)
Issued at 1249 AM CDT Tue May 7 2024

VFR conditions are expected at KHSV and KMSL through the
overnight hours until MVFR CIGS slide in ~11Z. Southwesterly winds
will pick up towards 15Z and gust to 20-25 kts. Introduced a
PROB30 for thunderstorms Tuesday afternoon, otherwise VFR
conditions will prevail.

&&

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

&&

$$

NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...70/DD
AVIATION...JMS