027
FXUS64 KBMX 090258
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
958 PM CDT Wed May 8 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE FOR POTENTIAL SEVERE STORMS INTO THURSDAY...
Issued at 820 PM CDT WED MAY 8 2024

Key Messages:

-Severe thunderstorms including tornadoes, damaging winds and
 large hail are possible overnight for a large part of Central
 Alabama. Storms will generally move in after 4 am from the
 north.

-Severe thunderstorm possibilities will continue into Thursday.
 Where the overnight storms boundary ends up after sunrise will
 dictate the approximate northern end of the threat area. All
 threats are possible on Thursday. Some modulation in intensity is
 anticipated during the morning hours with additional storms
 expected just ahead of this boundary. The boundary will
 gradually move southward with the severe threat ending by.

-It appears there will be another severe thunderstorm threat
 Thursday night after 10 pm for all of Central Alabama. All
 severe threats are again possible. The highest risk will be areas
 near and south of US 80/I-85.

First off, the severe thunderstorms ongoing this evening in the
Tennessee Valley. Central Alabama is not under a Tornado Watch and
it appears these storms will remain out of the area. There could
be a straggler near this watch, so remain vigilant especially if
you border this zone. We are current in a rather large warm sector
that has become quite unstable. An enhanced low level jet has
started increasing the past few hours while veering. This has
increased convergence in the Tennessee Valley. Central Alabama has
a lack of triggers this evening to get any sustained updrafts
going. Additionally, warmer mid and upper level temperatures were
to the south providing some capping.

It appears we will have to wait for the next and larger trigger.
This is the ever strengthening area of convection back in
Missouri, Arkansas, and Oklahoma. This boundary will approach our
northern areas after 4 am, and move north to south to near I-59 by
7 am. The low level winds increase areawide and the boundary will
act as a focus. We will have to watch for isolated cells ahead of
the boundary by sunrise.

As the sunrises, there will be modulation of the storms
individual strength. We have adjusted the area of main concern from
Demopolis to Alexander City to Roanoke and southward. The
boundary and cells ahead of the boundary will interact with
increasing instability through the morning. This keeps all threats
on the table but ends the overall threat sooner, after 2 pm.

Yet another upper short wave trough rides over Central Alabama
Thursday night near where the front will end up. Since there is
still rather unstable air south of the boundary, this may kick off
severe thunderstorms after 10 am area wide. The highest risk is
southwest.

Much of the previous discussion remains valid with some
adjustments in timing. Please see the graphics for further
detailed information.

75

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 122 PM CDT WED MAY 8 2024

Key Messages:

- Isolated showers and some thunderstorms this afternoon and
  evening, a few strong storms may develop.
- A Mesoscale Convective System dives southeast into the area
  after midnight tonight and pushes southeast through the morning
  and into the afternoon hours. While gradually weakening in the
  morning, it may re-intensify before it exists our southeast
  counties Thursday afternoon. Damaging winds will be the primary
  risk, with large hail and a few tornadoes being possible as
  well.
- Some thunderstorms may redevelop across North-Central Alabama
  Thursday late afternoon into the early evening that will have
  large hail potential, this risk will decrease in the evening as
  another MCS approaches our south-central counties from the west.


Thursday.

The MCS will continue moving southeast, affecting much of the
southern half of the area through the afternoon hours. There are
concerns for re-intensification of the MCS as it encounters a more
buoyant and unstable airmass due to daytime heating. The primary
risk will be with damaging straight-line winds, though large hail
will be possible and we can not rule out a tornado or two given
the combination of instability and wind shear associated with this
system.

There will remain chances for some redeveloping shower and
thunderstorm activity behind the MCS, most likely during the late
afternoon and into the early evening across at least the north-
central counties. Residual favorable shear profiles would support
a conditional risk for large hail in the heavier cores that manage
to develop.

This activity will give way to more widespread heavy convection
that will be approaching the southern half of the forecast area
from the west in the form of another MCS that will be pushing
across Mississippi during the afternoon and early evening hours,
which impacts to our south-central counties will be messaged in
the first portion of the long-term forecast discussion.

Through Thursday afternoon, expect winds outside of convection to
remain from the southwest at 7-14 mph. High temperatures will
range from the low 80s far east to around 90 southwest and far
south.

05

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 238 PM CDT WED MAY 8 2024

Conditions are shaping up for a secondary round of strong to severe
thunderstorms late Thursday night through Friday morning. This
activity will develop along the cold front which will be nearly
parallel to I-20 as a mid-level shortwave quickly moves east across
the area. The airmass will be very warm and unstable south of the
front with dewpoints in the lower to mid 70s and steep 7.5-8 C/km
lapse rates leading to large CAPE profiles (MLCAPE ~3500 J/kg).
Shear values will be amplified by the mid-level
speedmax/shortwave which will result in eff. bulk shear values
around 60 kts. This environment will foster intense convection
over the ArkLaTex and Lower MS River Valley this evening which
will rapidly grow upscale into a large MCS with damaging wind
potential maximized along embedded bowing segments as the system
moves east, generally following the instability gradient, across
the southern portions of Central Alabama early Friday morning.
There are questions regarding how far north the threat extends
given the uncertain position of the front and remnant cold pool
from the line of convection Thursday morning which could suppress
the greatest risk to the southern third of the area. Some hi-res
models indicate the potential for isolated cellular development
ahead of the MCS Thursday evening, but this is also more
uncertain. Nonetheless, anything that develops south of the cold
front will have the potential to become severe given the moist,
unstable environment. Damaging winds are by far the primary
threat, but intense updrafts may lead to large hail up to golf-
ball size in the Enhanced risk area. Straight hodographs indicate
a limited overall tornado risk outside of any microscale
interactions which could locally enhance directional shear.

The cluster of storms will begin to exit the area around 7 AM Friday
morning as the cold front continues to push south through the area,
bringing a much more pleasant airmass to the region. Humidity will
be lower on Saturday with highs in the upper 70s to lower 80s under
sunny skies. A mid-level ridge will move across the area over the
weekend as an upper-level low transitions from the Four Corners to
the Central Plains. Deep moisture returns on Monday, and models are
indicating increasing potential for another period of rainy and
stormy conditions through the early part of next week as a warm
front lifts north across the region.

86/Martin

&&

.AVIATION...
(00Z TAFS)
Issued at 715 PM CDT WED MAY 8 2024

An active pattern is setting up across the area through Thursday.
This evening should be the least impacted with VFR conditions and
little in the way of precipitation. Most activity remains north
of the terminals. As we head through the night, rain and
thunderstorms chances go up, mainly affecting the northern
terminals. At this same time, southerly flow continues and lower
MVFR ceilings will develop. The ceilings may drop to IFR at times.
The northern sites will see the ceilings rise to VFR around 17-18z
but still have some mention of thunder. The southern sites will
experience the MVFR ceilings developing just after 06z, but a
slower rise in rain chances. The storms get to the southern
terminals 16-18z, possibly sooner. Winds generally remain south
southwest around 10kts, with sporadic gusts to near 20 kts
throughout. Some of the individual storms may become severe with
tornadoes, damaging winds and large hail possible.

75

&&

.FIRE WEATHER...

Multiple rounds of showers and storms are expected to affect the
area beginning tonight through tomorrow. Rainfall amounts will
generally range from 1 to 2 inches. A drier airmass will return on
Friday as a cold front passes through the area with min RH of 35
to 40 percent on Saturday. 20ft winds will be out of the south-
southeast at 8 to 10 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     66  86  59  77 /  70  70  40  20
Anniston    68  84  63  78 /  60  70  50  30
Birmingham  71  87  63  78 /  60  70  50  20
Tuscaloosa  72  90  64  81 /  60  60  60  20
Calera      71  86  64  80 /  50  70  60  30
Auburn      71  82  68  82 /  40  60  60  50
Montgomery  73  89  68  83 /  30  60  70  50
Troy        72  90  67  83 /  30  60  70  70

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...75
LONG TERM....86/Martin
AVIATION...75