Tornado and Damaging Winds in Alabama, April 1, 2023

Area Forecast Discussion
National Weather Service Huntsville AL
1240 AM CDT Sat Apr 1 2023

...New AVIATION...

.NEAR TERM...
(Rest of tonight)
Issued at 1002 PM CDT Fri Mar 31 2023

A deep area of low pressure in the mid evening was moving
eastward across the IL/WI border. East of this low and a cold
front draped from west of Chicago to east of St Louis and Little
Rock, scattered to widespread showers and thunderstorms were in
progress. Numerous severe storms were noted from north of the Ohio
River to the southern Great Lakes, another from LA/AR to western
Tennessee. A tornadic storm as of this writing was roaring to the
ENE across Hardin county of southern TN. Another was moving over
far NW Mississippi just south of Memphis to SW TN. Given that
severe convection to our west and a potential of more forming this
evening, far NW Alabama including Lauderdale, Colbert, Franklin
counties are in Tornado Watch #97 (a rare Particularly Dangerous
Situation watch!).

No weather of consequence was occurring over the greater forecast
area as of this writing. Mild, with breezy to windy conditions
otherwise prevailed with temperatures mostly in the lower 70s.
Winds were from the south 20-30 mph with higher gusts. A Wind
Advisory remain in effect for the area until 1 PM Saturday.

New model input coming in continues to suggest this area just to
our north and west will be impacted by strong to severe storms
sometime in the overnight. Even this close to the onset of when
storms begin, exact timing ranged from after 10 PM to midnight.

Near and especially after midnight, a more/less solid line of
convection should move across the region from WNW to ESE. All
modes of severe weather is possible, with damaging wind gusts over
60 mph the main threat. Large hail and tornadoes cannot be ruled
out in a Quasi-Linear Convective System, squall line feature that
moves across the area. The models, both convective allowing and
older all hint at 0-3 helicity values in the 200-300 m/s range and
CAPES from 100-300, some spots higher; together with decent
widespread lift make it conducive for severe weather to occur.
Rough timing from new output has the stronger storms impacting NW
AL in the midnight to 1 AM timeframe, greater Huntsville area
2-4AM, and NE AL 3-5AM.

&&

.SHORT TERM...
(Saturday through Sunday night)
Issued at 102 PM CDT Fri Mar 31 2023

Sunny skies should quickly return Saturday morning. With the
actual cold front still to our west, decent warm air advection and
plenty of sunshine should allow highs to climb back into the lower
to mid 70s. The dry cold front itself will move through the area
late Saturday afternoon into the early evening hours. Some colder
air will advect into the region. A pressure gradient remains in
place though behind it Saturday night. So despite dewpoints dropping
into the lower to mid 30s, temperatures should hold a tad higher
in the upper 30s to around 40 degrees.

During the day on Sunday with a cooler start and some weak cold
air advection continuing, highs will only reach the mid 60s to
around 70 degrees in most locations. An approaching shortwave over
Arkansas should provide some moisture advection and more southerly
flow ahead of it Sunday night. This should bring dewpoints up
along with some increasing cloud cover. This will keep lows from
dropping much below the upper 40s to mid 50s.

&&

.LONG TERM...
(Monday through Friday)
Issued at 102 PM CDT Fri Mar 31 2023

At the start of Monday morning, a short wave trough will be moving
across the area during the morning hours, with a chance for light
rain for the area. Weakly convergent low-lvl flow may generate a few
showers or thunderstorms later on Monday into Monday night, but
forcing is generally weak during the late Monday period.

Generally inclement and potentially stormy weather will tend to
prevail for Tuesday through the end of next week, although details in
timing certainly remain to be resolved in the longer-term guidance
suite. The synoptic boundary serving as the dividing line between
modified polar/continental air and a humid, sub-tropical air mass
will continue to waver back and forth across the TN Valley as a
series of upr waves embedded in SWRLY flow aloft move across the
region. On Tuesday, it does appear likely that a deep trough will
take shape across the western CONUS, with cyclogenesis in the central
High Plains. The main synoptic boundary will probably be well to our
north at this time with our region deep into the warm sector of the
developing system. Some models/ensembles eject upr short waves and a
plume of steep mid-lvl lapse rates out of the SW/NRN Mexico on
Tuesday into Tuesday night, which may be capable of instigating
strong shower/thunderstorm development. Coverage of any activity on
Tuesday/Tuesday night is quite uncertain though considering the
better part of the forcing will probably exist to our north in the
mid-Miss Valley into the Midwest. POPs are tailored accordingly,
indicating higher values along our northern border. What is
appearing more certain is that the attendant cold front will move
across the area sometime on Wednesday...whether during the morning or
afternoon is uncertain at this time. However, the timing may end up
having severe weather implications for the area. A potential
combination of shear/instability in the warm sector ahead of the
front offers a recipe capable of producing severe weather just
ahead/along the front. But, the best dynamic forcing appears likely
to be to our north according to wind field progs indicating a 60+ kt
low-lvl jet located in the OH Valley, although 50 kts could be
realized here. Nevertheless, specifics regarding timing and placement
of features with this system will be watched going forward.

There are some indications that the sfc boundary will pass to our
southeast on Wednesday. However, continued SW flow aloft may prevail
across the shallow cooler air mass that moves into the region. This
could result in a continuation of periods of rain with a few
embedded thunderstorms at times into the late week.

&&

.AVIATION...
(06Z TAFS)
Issued at 1240 AM CDT Sat Apr 1 2023

Stormy conditions will impact the terminals over the next few
hours, as strong to severe showers and thunderstorms extending
from west of KBNA and KTUP move eastward. This line should reach
KMSL in the hour or so, and KHSV in 1-2 hours. Variable winds
with gusts +40kt and brief VSBY reductions to IFR are possible in
the stronger storms. The showers should end quickly as they head
east, with VFR weather returning. Strong winds however will
continue for the rest of the night through the early afternoon.
SW-W winds after the showers pass will become westerly, then W-NW
during the afternoon, slowly subsiding in the early evening.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory until 1 PM CDT this afternoon for ALZ001>010-016.

TN...Wind Advisory until 1 PM CDT this afternoon for TNZ076-096-097.

&&

NEAR TERM...RSB
SHORT TERM....KTW
LONG TERM....KDW
AVIATION...RSB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
210 AM CDT SAT APR 1 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0137 AM     TORNADO          6 N RED BAY             34.53N 88.14W
04/01/2023                   FRANKLIN           AL   OFFICIAL NWS OBS

            A TORNADO DEBRIS SIGNATURE (TDS) WAS
            DETECTED ON GWX RADAR.

&&

HC