.SHORT TERM...
(This afternoon through Saturday night)
Issued at 1226 PM CDT FR MAR 14 2025
BLUF: A multi-faceted severe weather event will feature at least two
rounds, one beginning early tomorrow morning, and the second
arriving Saturday afternoon through early Sunday morning. A
significant outbreak of severe weather is expected with all modes
of severe weather, including strong and long-lived tornadoes.
A potent mid-level shortwave will move across the Central Plains
today. Partly sunny and gradually warming conditions are expected
across Central Alabama this afternoon with a steady stream of
south to southwesterly low-level flow which will allow
temperatures to warm into the upper 70s to lower 80s across the
area. This will set the stage for ample thermodynamics heading
into tonight as the shortwave and 90-110kt 500mb jet eject across
the Midwest and Midsouth regions, initiating the first wave of
convection across the Lower MS River Valley. While upper-level
forcing will be maximized to our northwest over the Midwest
region, it does look like our parameter space will be able to
compensate for that across the Southeast. There's a mixed bag of
potential outcomes with some hi-res models suggesting scattered to
numerous thunderstorm development, with supercells, while other
models are resolving a stronger cap in a warm, dry layer beginning
around 800mb, and therefore less convective initiation. However,
as a 50-60kt LLJ nudges into the area around midnight, we suspect
there will be a surge in moisture quality which should allow for
at least scattered thunderstorms to develop, initially over
Mississippi, then east into western portions of Central Alabama
through early Saturday morning. Despite there being a couple
limiting factors, there is a high ceiling, and storms that break
the cap will be able to take on supercellular characteristics
given the strong wind shear, and steep mid-level lapse rates.
Could certainly see the potential for tornadoes tonight, some
strong. So it's important that this first wave doesn't sneak up on
people. Make sure your method of receiving warnings is loud
enough to wake you up. The threat will be less for areas east of
I-65 where the air will be drier, but it's important to maintain
weather awareness tonight regardless.
After somewhat of a brief lull from the late morning hours through
midday, the second, more widespread round, and what is being
advertised as the "main event," will rapidly develop to our west in
response to a deepening longwave trough over the Central CONUS and a
reinvigorated 500mb jet across southern Texas into the Lower MS
River Valley. In this case, forcing will be maximized across our
region with Central Alabama directly in the right entrance region of
the upper-level jet. Unfortunately, hi-res models are pointing more
towards the development of a pristine warm sector as mid to upper
60s dewpoints blanket across the area. Factor this in with
temperatures in the mid to upper 70s, and some of the steepest mid-
level lapse rates i've seen in a while (7.5-8 C/km 700-500mb LR),
and we're looking at a primed warm sector characterized by 2000-2500
J/kg of SBCAPE overlapped with intense dynamics. In fact, pressure
falls associated with a surface low over the Midsouth, and a
strengthening 50-70 kt 850mb jet will contribute to ideal wind
dynamics for tornadoes with plenty of deep and low-level curvature
evident on forecast hodographs. By all accounts, conditions are
shaping up to support an outbreak of significant severe weather,
potentially on a scale that we haven't seen for quite some time.
Several hi-res models are resolving supercell structures, some
discrete, tracking across the area tomorrow afternoon, and this has
been a common theme in forecast guidance over the past few days.
It's likely we could see several strong tornadoes tomorrow, perhaps
some long-track. This combination of ingredients will also support
damaging straight-line winds up to 70 mph, and due to the cold
temperatures aloft and robust updrafts, storms could contain large
hail up to 2".
On top of everything else, there will be a risk for flash flooding
across northwest portions of the area where there will be the
most overlap from the early morning storms to afternoon storms.
High precipitation rates and training thunderstorms will lead to
rainfall accumulations of 3 to 5 inches with some locally higher
amounts possible. Although we've been dry as of late, HREF probs
are indicating low to potentially medium chances of exceeding 5
inches of rainfall across portions of northwest Alabama, so that's
something we will definitely have to watch for as well, and a
Flood Watch has been issued for those areas. Additionally, non
thunderstorm wind gusts are expected to increase to around 35 to
40 mph tomorrow afternoon with strong mixing expected in the warm
sector. A Wind Advisory will likely need to be coordinated soon.
The severe threat will focus east of I-65 by tomorrow evening as
storms potentially take on more of a linear orientation with time,
although embedded supercells will still be possible. Expect the
threat to end by 3 AM Sunday in the southeast as the cold front
begins to pass through the area with the surface low lifting towards
the Ohio Valley.
86/Martin
