674
FXUS64 KHUN 231115
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
615 AM CDT Thu May 23 2024

...New AVIATION...

.NEAR TERM...
(Today)
Issued at 441 AM CDT Thu May 23 2024

The convective cluster that produced primarily large hail and
damaging winds in Texas and Louisiana last night has weakened
significantly. It continues to push east well south of the area
in the form of a shield of stratiform rain moving through
east central MS. A shield of light rain extends northward from
this convective system into central Alabama. Further north, mainly
virga is occurring over portions of NW Alabama. Kept the previous
thinking (20 PoP) that most of the precipitation on the northern
edge system as it continues to move east will not make it into
much of northern Alabama. The exception to this may be Cullman
county, where brief light rain or a few sprinkles may occur
towards daybreak.

Most guidance depict the forcing producing this convective system
to our south decaying and falling apart as it approaches eastern
Mississippi and western Alabama around daybreak. Thus PoP was kept
with a lowering trend towards 15 percent then.

Shortly after daybreak, models show some additional development of
disturbances aloft along the upper level trough axis that is
stalled just to our northwest over western Tennessee into
northeastern Texas. These move ENE along this trough axis today
before maybe sinking southeast some this evening. This should
concentrate the bulk of the precipitation today more over
Tennessee and maybe portions of NW Alabama. Locally heavy rainfall
would be most likely in those locations. The fairly fast mean 0-6
km flow combined with where the main axis these disturbances are
traversing hints that any flooding potential may remain in
Tennessee today. Lapse rates don`t look great in guidance, but
shear, DCAPE, and instability do look like enough of a combination
that a few severe storms could develop later this afternoon into
the evening hours (again most likely in Tennessee). With a warm
start (temperatures this morning in the upper 60s to lower 70s
when you wake up, Despite some fairly widespread cloud cover this
morning into the early afternoon hours, highs will likely still be
able to climb into the lower to mid 80s in most locations near
and south of the Tennessee River. If sunshine is more widespread
than expected, highs could be a few degrees higher in the mid to
upper 80s in those locations.

&&

.SHORT TERM...
(Tonight through Saturday night)
Issued at 441 AM CDT Thu May 23 2024

With the loss of daytime heating, convection moving south from
southern middle Tennessee should fall apart around midnight. But
it might take that long given some of the remaining forcing moving
south. A few of those storms could remain severe before dissipating.
Main threat may shift more to large hail than damaging winds.

We will have to watch for fog development overnight as winds are
forecast to be very light. Persistent cloudy conditions though may
keep fog from being very widespread or dense.

A much stronger shortwave is progged by most guidance to develop
over Arkansas and push ENE towards the area on late Thursday night
into Friday. Very strong forcing at 700 mb is seen with this
piece of energy aloft. As it moves east early Friday morning in
to northwestern Alabama and western Tennessee, instability will be
in place near and ahead of it (1000 J/kG to 2000 J/KG of MUCAPE)
along with mid level lapse rates between 7.0 and 8.0 degrees/km.
This instability only increases in guidance into the afternoon
hours (2000 to 3000 J/KG). DCAPE is most models sounding is
between 1000 and 1200 J/KG as this disturbance continues to move
east into NW Alabama with ample shear to support organized severe
thunderstorm development. Therefore, some storms could become
severe during the late morning into the afternoon hours producing
large hail or damaging winds. There is a very low chance of
tornado or two given 0-3 km helicity values, but damaging wind and
large hail are expected to be the main threats. Given the
expected cloud cover and more widespread nature of showers and
storms, high should be cooler only reaching the 79 to 85 degree
range.

Weaker shortwaves are shown in models lingering into the evening
upstream of the area aloft. Shear weakens Friday night, but with
decent elevated MUCAPE lingering (~1500 to 2000 J/KG) at least
strong storms could linger into the nighttime hours. It will
remain humid overnight with lows only dropping to between 65 and
70 degrees in most locations.

During the morning hours on Saturday upper level ridging builds
over the area behind the departed shortwave aloft well to our east
over the Carolinas. This should help suppress lift and weaken
upstream disturbances. Expect scattered showers and thunderstorms
to continue, but coverage of showers and storms should be less as
bulk shear remains weak (<25 knots). Not expecting severe storms
until maybe in the afternoon, when another strong shortwave moves
from Mississippi moves into the area. Shear will remain weak as
this occurs, but instability will be between 2000 and 3000 J/KG
and mid level lapse rates around 8 degrees/km. So damaging winds
and large hail cannot be ruled out in the strongest storms. With
the more scattered nature of the activity in the morning, more
sunshine will likely be seen at times. So highs in the mid 80s
seem reasonable.

Lower chances (20 to 40%) of showers and storms are expected
Saturday night, as the forcing moves east of the area into
Georgia and the Carolinas. This should give us a break from the
period of showers and storms overnight into Sunday.

However, a potent storm system that develops in models late
Saturday night into Sunday over the Upper Midwest moving into the
western Great Lakes region will be the next impetus for additional
showers and thunderstorm activity. This round looks to be more
organized and severe.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 441 AM CDT Thu May 23 2024

We will likely get some additional cloudy conditions and maybe an
isolated shower or thunderstorm with a pre-frontal trough axis
ahead of this system on Sunday. However, overall should be a rain
free day and hot with highs in the upper 80s to 90 degrees.

This changes though as the main cold front pushes southeast Sunday
night into the area. Very steep lapse rates, strong shear, high
DCAPE values, and strong instability (3000 to 4000 J/KG) will
provide the impetus for a MCS that develops along this front as it
pushes into and through the area overnight into Monday morning.
Saturated soils by then could produce a more enhanced threat for
flash flooding or river flooding from this rainfall.

Models differ on how quickly this system pushes through the area
though, so activity cloud linger into the afternoon on Monday.
However, the atmosphere will likely be worked over from earlier
convection earlier in the day, so severe weather should not be
much of an issue if that occurs.

Finally northwest flow aloft and dry weather builds back into the
area Tuesday into Wednesday. Highs will drop back into the upper
70s to lower 80s again thankfully with lows dropping back into
the mid 50s to lower 60s.

&&

.AVIATION...
(12Z TAFS)
Issued at 606 AM CDT Thu May 23 2024

VFR conditions will continue at both terminals despite abundant
cloud cover. Expect this cloud cover to hang around through 22Z
at both terminals. A tempo group for MVFR VSBYS was included for
scattered or bit more widespread convection that may push into
that terminal between 17Z and 21Z. Further east at KHSV, included
a VCTS between 18Z and 22Z, but confidence on coverage is lower
and thus the possibility of a -TSRA directly impacting that
terminal.

&&

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

$$

NEAR TERM...KTW
SHORT TERM....KTW
LONG TERM....KTW
AVIATION...KTW