895
FXUS64 KHUN 050951
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
451 AM CDT Sun May 5 2024

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

.NEAR TERM...
(Today)
Issued at 451 AM CDT Sun May 5 2024

Isolated-widely scattered convective cells which developed late
yesterday evening across northeast AL/southern Middle TN have
since dissipated as this activity was forced by a weakening mid-
level vort max tracking eastward and away from the region. Given
the combination of clear skies, calm winds and rich moisture in
the boundary layer, concern for the remainder of the early morning
will be locally dense fog, which has warranted an SPS that runs
thru 14Z.

Over the course of the day, high-level debris clouds will spread
eastward from a broad convective regime (currently in progress
across the southern Plains) that is occurring in conjunction with
a pronounced mid-level shortwave trough over the Red River Valley
of OK/TX. Although the onset of broken-overcast cloud layers aloft
this afternoon will limit diurnal warming to some extent, we
still expect highs to reach the m-u 80s for most valley locations,
with development of isolated showers and thunderstorms possible
shortly after Noon. It still appears as if the leading edge of the
convective regime over the southern Plains will spread
northeastward throughout the day with the mid-level trough and as
a warm front lifts northeastward from the central Gulf Coast (in
response to a deepening lee cyclone across eastern portions of
MT/WY). Flow at the 500-mb level will back to SW and strengthen to
30-35 knots ahead of the trough, supporting the risk for
organized convective structures as the leading edge of this
precipitation regime enters the southwestern portion of the CWFA
between 22-00Z, and with MLCAPE likely to be in the 1000-1500 J/kg
range, a few strong-marginally severe thunderstorms will be
possible, with the main threats being locally damaging wind gusts
and large hail.

&&

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 451 AM CDT Sun May 5 2024

Guidance from the 00Z CAMs suggests that the risk for a few
strong-severe thunderstorms may continue for at least an hour or
so beyond sunset as the leading edge of the precipitation regime
(discussed above) spreads further northeastward across the local
area. However, nocturnal cooling of the boundary layer will
contribute to a gradual weakening trend with time over the course
of the evening, with a transition to widespread rain and embedded
thunderstorms anticipated by late this evening. It still appears
as if the warm front will make slow but steady northeastward
progress across the region and into southern KY during the early
morning hours, with widespread precipitation likely coming to an
end from SW-to-NE by 12Z Monday. An airmass of even greater
moisture content will be advected northeastward into the TN Valley
throughout the day as SSW low-level flow strengthens, with
dewpoints in the u60s-l70s supporting redevelopment of scattered
showers and storms in the vicinity of a subtle low-level
streamline confluence axis Monday afternoon even as abundant cloud
cover holds temps in the l-m 80s.

On Monday night, a mid-level ridge will translate eastward across
the forecast area downstream from a nearly stationary deep-layer
cyclone across the northern High Plains. Although this should
result in a lower coverage of nocturnal convection, we will
maintain a low-medium chance POP in the grids due to the
strengthening lower tropospheric warm/moist advection regime in
place across the region. Otherwise, it will be a warm, breezy and
humid night, with lows in the upper 60s for all but a small
portion of northeast AL.

The warm/moist advection regime discussed in the previous
paragraph should yield a gradual increase in the coverage of
mainly afternoon thunderstorms on Tuesday as temps warm into the
mid 80s. However, with little evidence of a well-defined source of
synoptic scale lift, we will keep POPs in the chance range at
this point. Regardless of storm coverage, conditions will become
increasingly favorable for strong-severe thunderstorms beginning
on Tuesday as WSW flow aloft will increase into the 30-40 knot
range in the wake of the departing mid-level ridge. Not only will
this improve vertical wind profiles, but it will also result in
steeper lapse rates aloft, which may yield CAPE in the 2500-3500
J/kg range given surface dewpoints in the lower 70s.

Although the details remain unclear at this point, a greater risk
for severe thunderstorms may materialize late Tuesday night/early
Wednesday morning, originating from convection that should
develop across a broad region from eastern OK/western AR into the
Lower OH Valley Tuesday evening as frontal wave begins to spread
eastward off the southern High Plains and into OK/KS. This
activity may grow into a broken MCS (or perhaps several smaller
but highly organized storm clusters) that would subsequently
propagate southeastward into our region early Wednesday morning.
Should this occur, the combination of shear and instability would
once again support damaging winds and large hail.

&&

.LONG TERM...
(Wednesday through Saturday)
Issued at 451 AM CDT Sun May 5 2024

Overall, there has been very little change in extended range
guidance from the global models this morning, with any nocturnal
storm clusters that survive as far southeastward as the TN Valley
early Wednesday morning expected to dissipate rather quickly by
mid-day. Attention will then refocus to the northwest of our
region, where explosive development of convection is expected to
occur on Wednesday afternoon as the frontal wave (discussed above)
shifts northeastward into MO. One region of potential convective
development will be downstream from the path of the surface low
(from eastern KS into central IL), with another region of
potential development along the trailing cold front extending
southwestward into northeastern TX. It still appears as if this
activity will grow upscale into a rather potent MCS that should
track southeastward into our CWFA early Thursday morning. With
mid-level WSW flow expected to easily be in the 45-50 knot range
at this point atop a southwesterly low-level jet of 30-40 knots,
all severe hazards (including tornadoes) will be possible with
this convective system.

Yet another round of rain and thunderstorms may occur with the
passage of a cold front Thursday night, but at least low-level
shear will be weaker with this final round, and airmass recovery
may not be sufficient to support a risk of strong-severe storms. A
refreshing surge of cooler/drier continental air will spread
southeastward in the wake of the cold front, bringing dewpoints
into the 40s for much of next weekend.

&&

.AVIATION...
(06Z TAFS)
Issued at 1248 AM CDT Sun May 5 2024

Isolated-widely sct SHRA/TSRA which developed to the immediate
N/E of HSV late Sat evening will continue to progress eastward,
and should not impact the airport. However, with mostly clear
skies and calm winds anticipated for much of the early morning
period, abundant low-lvl moisture will support the development of
MVFR vsby reductions in lgt BR/FG, and this has been included in
TEMPO groups at both HSV/MSL from 9-13Z. A diurnal Cu field will
redevelop by 16-18Z, with isolated showers and storms possible
invof the terminals once again beginning early this aftn. That
said, a more widespread coverage of rain and TSRA will likely
begin across northwest AL very late this aftn and spread
northeastward with time during the evening hours, potentially
bringing MVFR cigs/vsby in pockets of locally heavy rainfall.

&&

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

&&

$$

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