ACUS01 KWNS 211949
SWODY1
SPC AC 211947

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0247 PM CDT Wed May 21 2025

Valid 212000Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE OZARKS...

...SUMMARY...
Isolated strong to severe storms remain possible in the Upper Ohio
Valley, parts of eastern North Carolina, North Florida, parts of the
central Plains, and Deep South Texas. Additional, scattered strong
to severe storms are possible in the Ozarks this evening.

...20Z Update...
Severe probabilities have been adjusted based on current
observational/convective trends. A narrow zone in western
Pennsylvania will remain favorable in the short term for a brief
tornado prior to precipitation stabilizing the low levels and
low-level winds veering. Scattered elevated convection is still
expected across parts of the Ozarks later this evening. See the
previous forecast for additional details.

..Wendt.. 05/21/2025

.PREV DISCUSSION... /ISSUED 1131 AM CDT Wed May 21 2025/

...Eastern North Carolina/southern Virginia...
In the wake of early morning convection, air mass
recovery/destabilization will occur today in vicinity of the
eastward-transitioning surface wave and in vicinity of the roughly
west/east-oriented surface boundary located near/south of the
Virginia/North Carolina border. Drying westerly low-level
trajectories will exist to the south of the front and behind the
surface wave, with severe-storm favorable ingredients/potential
development tending to focus across far northeast North Carolina
where moderate buoyancy will be maximized with strong westerlies
aloft (40+ kt effective shear). While severe storm
coverage/likelihood may not be as high as previously thought, some
potential for large hail, damaging wind gusts and possibly a tornado
will still exist on an isolated basis.

...Ozarks/Mid-South...
While rich boundary-layer moisture will remain confined across south
Texas and Louisiana, a strengthening low-level baroclinic zone will
focus near the Kansas/Oklahoma border east-southeast into the
Mid-South. Guidance is rather consistent in developing at least
elevated convection to the cool side of this zone by evening. This
will be coincident with an intensifying mid-level speed max.
Forecast soundings depict potentially very strong mid to upper-level
speed shear within the slightly north of west flow regime. Coupled
with steep mid-level lapse rates, this setup could yield a few
elevated supercells capable of large hail and perhaps locally
damaging winds.

...Central Plains...
A mid-level vorticity lobe initially over Wyoming this morning will
dig east-southeastward into the lower Missouri Valley by early
evening amidst west-northwesterly flow aloft. Heating will result in
very steep 0-3 km lapse rates by mid afternoon with several hundred
J/kg SBCAPE. Elongated hodographs will support quick-moving cells
capable of an isolated risk for severe wind gusts during the late
afternoon through around sunset (roughly 20-01z).

...Upper Ohio Valley including PA/OH/WV border region...
A corridor of modest boundary-layer heating is expected ahead of the
primary surface cyclone drifting across northern Ohio toward Lake
Erie. Coupled with cooling mid-level temperatures, weak
surface-based buoyancy is expected by midday into the afternoon.
Deep-layer shear will not be strong given proximity to the mid-level
trough, but should be adequate for weak/transient mid-level
rotation. With numerous thunderstorms expected, small to marginally
severe hail and isolated damaging winds are anticipated. A brief
tornado or two is also possible with storms near the warm front,
before convection weakens as it moves east-northeastward into
less-buoyant surface conditions.

...North Florida and southern Georgia...
Along the southeastward-moving cold front, moderate buoyancy is
expected ahead of the front.  A veered low-level wind profile will
limit effective bulk shear, but scattered thunderstorms could yield
multicells and perhaps a transient supercell. Isolated damaging
winds and marginally severe hail are possible with the stronger
storms. For additional short-term details, see Mesoscale Discussion
920.

...Far southern Louisiana/far southern Mississippi...
Sufficient residual elevated buoyancy in the immediate post-frontal
environment may allow for some storms to produce hail to near severe
levels, mostly over just the next few hours this afternoon and on a
very isolated basis.

...Deep South Texas...
A very moist and unstable air mass (2000-4000 J/kg MLCAPE later
today) exists across the region, aside from some higher cloud cover
spreading into the region via a slowly approaching and weakening
convective complex south of the international border. Additional
convection will likely develop in adjacent Mexico over the higher
terrain this afternoon, and some of these storms may spread east
across the lower Rio Grande Valley this evening. Isolated large hail
and severe-caliber wind gusts may accompany these storms.

$$