723
FXUS64 KBMX 270225
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
925 PM CDT Sun May 26 2024

...New SHORT TERM, AVIATION...

.SHORT TERM...
(Tonight through Tuesday)
Issued at 838 PM CDT SUN MAY 26 2024

KEY MESSAGES...

-Severe thunderstorms including tornadoes, damaging winds, and
 large hail are possible overnight. The best chance north of I-20
 after 2 am.

-Severe thunderstorms possible again on Memorial Day, mainly in
 the afternoon and evening. The main threats will be damaging
 winds and large hail. It appears the tornado threat lessens with
 time as the storms move from north to south.

Monitoring the severe thunderstorms developing north across the
Ohio Valley this evening. Some activity is just beginning in the
Missouri Bootheel with hints of additional development in northern
Arkansas. Hi Res CAMS are starting agree with the timing of after
2am for northwestern areas near Hamilton, with potential isolated
development ahead of a more organized line. Bulk Shear values
around 60kts will be more than enough for organized storms. 0-3km SRH
values 200-300 in spots, SBCAPE 2000-3000 in spots while
hodographs support tornadoes late tonight. Therefore, will hold
the timing and threats as they are. Please have multiple ways to
receive watches and warnings especially during the overnight
hours.

Some differences appear in the model output and ultimate
evolution of the storms during the morning hours on Memorial Day.
Some weakening is expected as the storms enter the I-20 corridor
and then re-intensification with chances of severe after noon,
though Bulk Shear decreases. The biggest questions at this time
are the where storms start re-intensification or if they weaken
at all and storms continue from overnight and exit quicker to the
southeast. This will have an effect on how large an area has a
severe risk. The only thing that does look fairly agreeable is
that the winds veer with time and the tornado threat should
decrease with time. At any rate, be aware of the possibility of
severe thunderstorms especially with outdoor activities on
Memorial Day.

No significant changes to the ongoing forecast and overall
message.

75

Previous short-term discussion:
(This evening through Monday)
Issued at 1228 PM CDT SUN MAY 26 2024

Tonight, the environment will become better prepped for storms
ahead of a cold front expected to move through the area on Monday,
with the main area of increasing instability, PW, and shear
across the northwestern third of the state, closer to that front.
A line of storms is expected to move east and southeast overnight
into the early morning on Monday. While the storms move through
northwestern Alabama, PW values will be around 2 inches, which is
well above max for this time of year, with instabilities between
2500 and 3000 j/kg. 0-6 km shear will be very strong, values up to
80 kts showing on several models across the northern most
counties, and 0-1 km shear around 30 kts. The storms along this
line may stay strong to severe as they move into the northwestern
counties of Central Alabama around 2 am Monday morning, and then
as they move southeast. Damaging winds and large hail will be a
threat, and with the amount of wind shear present, a tornado is
possible.

As the line moves to the east and south, instabilities should
quickly decrease, and shear should weaken through the morning.
While storms could remain strong, the severe threat will greatly
diminish by the time the storms reach the I20 corridor. Areas
south of I20 may see a strong storm if the line can move into the
area faster Monday morning, otherwise, these areas will see
scattered showers with a few isolated thunderstorms.

This area of activity should be east of the area by around 8 am
Monday morning with the rest of the morning and early afternoon
remaining dry. The afternoon on Monday brings lower confidence.
Almost all CAMs, (outlier is the HRRR) show a lack of convection
developing through the afternoon. Wind shear decreases greatly,
and PW values begin to decrease through the afternoon as the
frontal boundary moves from northwest to southeast through the
afternoon on Monday. Due to a combination of morning activity
across the northern half of the state, as well as drier air moving
quickly into these areas from the northwest, would expect
decreasing chances for severe storms across the northwest through
the afternoon.

However, instabilities across the southeastern half of the state
will be between 3500 and 4000 j/kg and LI values around -9. Wind
profiles show very little strength or turning, though upper level
dynamics show divergence aloft. Right now will advertise severe
thunderstorms with damaging winds and large hail the main threat.
If storms can develop and tap into the right combination of
instability and forcing, severe thunderstorms seem to be a given.
Though models are pessimistic as to much if any coverage across
most of the area. In areas south of I85, there does appear to be
decent consensus of a line of storms developing in the mid to
late afternoon, lasting through the evening. With instabilities so
high, will expect a greater chance for strong to severe
thunderstorms in these areas.

24

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 402 PM CDT SUN MAY 26 2024

The main changes to the extended are that guidance is indicating
a faster exit of the system out of C AL on Mon evening. So,
although we are still thinking that there is a severe risk on
Monday, storms will likely only still be around in the far SE
counties to have risk by Mon evening in 0-3z timeframe. If faster
trend continues, this timing may need further adjustments on the
mid shift. Otherwise, added some minor isolated heat of the day
pops for Wed/Thu in a few spots, but nothing big. More significant
rain chances return by next weekend with the approach of an upper
system into the SE US.

08

Previous long-term discussion:
(Monday night through next Saturday)
Issued at 340 AM CDT SUN MAY 26 2024

The frontal boundary should be moving through Central AL Monday
evening/night, continuing to support strong to severe storms for a
few hours Monday evening before exiting to our southeast before
midnight.

Drier weather expected Tuesday through the end of the week. Some
guidance tries to hint at a few waves moving through the ridge to
our west Wednesday into Thursday, but confidence isn`t there to
included in the forecast at this time. Most indications are that the
low level ridge that builds in across the deep south suppresses much
of the thunderstorm activity under the northwesterly flow aloft.

As we approach next weekend, the ridge slowly slides to our east,
allowing a few shortwaves to slide through to our north, which will
lead to increasing rain/storm chances Friday night through Saturday,
but timing of these waves is highly uncertain and the forecast is
likely to change in coming days.

25/Owen

&&

.AVIATION...
(00Z TAFS)
Issued at 838 PM CDT SUN MAY 26 2024

VFR conditions will exist through 06-08z for most terminals. Then
the conditions will begin changing. Lower ceilings/vis begin
affecting the southern MGM/TOI after 06z while some lower ceilings
and rain chances enter the picture north after 08z. Thereafter,
showers and storms will traverse from north to south through the
period. The specific evolution of the storms will need to be
refined at a later time and added to the terminals. Right now,
mentioning PROB30 thunder and MVFR/IFR ceilings. Winds will
increase overnight and be south to southwest around 10kts. Some
gusts are possible at times to around 20kts outside storms.

75

&&

.FIRE WEATHER...

Scattered showers and thunderstorms are expected again late
tonight into Monday. 20 foot winds will be from the south to
southwest at 6 to 12 mph today. Min RH values will in the upper
40s or above 50 percent through Monday, with overnight recoveries
near 100%. Drier air builds in Tuesday with only isolated
convection possible for Tuesday and Wednesday with afternoon
heating.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     69  88  61  88 /  60  40  10   0
Anniston    71  88  63  87 /  40  40  10   0
Birmingham  72  90  65  88 /  50  30  10   0
Tuscaloosa  72  91  65  90 /  50  30  10   0
Calera      73  90  65  89 /  40  30  10   0
Auburn      72  86  67  87 /   0  50  20   0
Montgomery  74  90  67  90 /  10  50  20   0
Troy        72  89  68  90 /   0  50  30   0

&&

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

$$

SHORT TERM...75
LONG TERM....08
AVIATION...75