523
ACUS01 KWNS 201247
SWODY1
SPC AC 201246

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Sun Apr 20 2025

Valid 201300Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
ARKANSAS AND MISSOURI...

...SUMMARY...
Severe thunderstorms are expected today across parts of the ArkLaTex
into the Ozarks and mid Mississippi Valley, mainly this afternoon
and evening. The best corridor for tornadoes (some of which could be
strong) and scattered to numerous damaging winds should exist from
central/northern Arkansas into Missouri.

...ArkLaTex into the Ozarks and Mid Mississippi Valley...
Extensive convection has occurred overnight and early this morning
across the southern Plains into the Ozarks and mid MS Valley.
Ongoing thunderstorms across south-central TX are expected to
continue weakening over the next couple of hours as they encounter a
strongly capped airmass. Activity over eastern OK into western AR
and MO may pose an isolated hail/wind threat this morning, although
instability will tend to remain weak for at least a few more hours.
Otherwise, a strong mid-level shortwave trough will continue to
eject northeastward from the southern Plains across the Ozarks and
mid MS Valley through the period. An attendant 60-90 kt mid-level
jet will likewise spread northeastward across eastern OK/KS and the
Ozarks through the day. A weak surface low over OK this morning will
also develop northeastward to northern MO by this evening, while a
cold front continues moving eastward over the southern Plains
towards the ArkLaTex.

Ongoing cloudiness and precipitation lend some uncertainty regarding
the degree of destabilization that will occur by this afternoon
across the developing warm sector. Still, most guidance shows that
at least low 60s surface dewpoints and related low-level moisture
will attempt to stream northward across eastern OK and AR/MO in
tandem with a strong southerly low-level jet today. Although daytime
heating will likely be hampered to some extent, even 500-1000 J/kg
of MLCAPE will support surface-based thunderstorms by this
afternoon. This destabilization appears likely to occur in a narrow
corridor along and just ahead of the surface low and related cold
front. Rather strong deep-layer shear will easily support organized
updrafts, including the potential for a mix of supercells and broken
line segments.

Current expectations are for robust thunderstorms to develop
along/near the front across eastern OK and vicinity by early
afternoon (17-19Z), as pronounced large-scale ascent associated with
the ejecting shortwave trough impinges on the warm sector. Given a
weakly unstable and strongly sheared environment, this convection
should intensify fairly quickly as it moves east-northeastward into
AR/MO. The linear forcing of the front suggests that a line or
cluster mode should occur, although some high-resolution guidance
does show more of a broken line of supercells given the strength of
the deep-layer shear. Regardless, the threat for scattered to
numerous severe/damaging winds and tornadoes will increase this
afternoon and evening across the Enhanced Risk and vicinity, as a
40-55 kt southerly low-level jet aids in large 0-3 km hodograph
curvature and elongation. Given the forecast strength of the
low-level shear, some of these tornadoes could be strong (EF-2+),
especially if a mixed supercell/cluster mode can be maintained
versus linear. Hail may also occur with any sustained supercells.
The overall severe threat this evening and overnight will be
tempered on the north by limited low-level moisture and instability,
and on the east by gradually increasing MLCIN.

..Gleason/Broyles.. 04/20/2025

$$