LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1248 AM CDT Sat Apr 15 2023
Valid 151200Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY...
...SUMMARY...
Severe thunderstorms -- capable of producing large to very large
hail and damaging wind gusts, as well as a couple of tornadoes --
are possible from Missouri and the Mid-Mississippi Valley, southward
to the Lower Mississippi Valley and upper Texas Coast.
...Mid MS Valley/AR...
Pronounced mid-level short-wave trough is currently located over
CO/NM. This feature will eject into the central/southern Plains as a
strengthening 500mb speed max translates across central OK by early
evening then into AR, increasing to near 85kt by the end of the
period. In response to this feature, weak surface low is forecast to
track from northern OK - northern MO - into northern IL Saturday
evening. While the surface reflection is not expected to be
particularly intense, 60F surface dew point should advance to near
I70 across MO by 18z, perhaps surging into west-central IL by early
evening ahead of the surface low.
Early this morning, several clusters of thunderstorms have evolved
over the central Plains region into western IA. Remnants of this
activity should propagate into the mid MS Valley by the start of the
day1 period and continue weakening as it spreads toward IL by mid
day. Of more concern will be renewed convection that will evolve
along/ahead of the surface low/cold front by early afternoon across
eastern KS/western MO. Forecast soundings exhibit very steep
surface-9km lapse rates which will aid buoyancy within a strongly
sheared environment. MLCAPE values could approach 3000 J/kg across
much of this region and supercells are expected to evolve fairly
early ahead of the short wave. Deep-layer flow is somewhat veered so
SRH values are not expected to be that strong. However, very large
hail should be noted with the strongest supercells. As the front
advances east, scattered convection may grow upscale into a QLCS
with embedded supercells as it advances toward the MS River. Intense
12hr mid-level height falls across the mid MS Valley during the
overnight hours may encourage strong convection to surge a bit
farther east across IL toward IN during the overnight hours. In
addition to very large hail, damaging winds and the threat for at
least a couple of tornado can be expected.
...Gulf Coast Region...
Latest satellite imagery depicts a short-wave trough over northeast
Mexico ejecting toward south TX, in line with latest model guidance.
This feature is expected to contribute to an expanding cluster of
convection that should propagate from the middle/upper TX Coast,
east along/just offshore of the central Gulf Coast. Northern
portions of this MCS should advance across the FL Panhandle during
the mid/late afternoon. Hail/wind are the primary risks with this
complex.
Secondary convective development is possible later in the day along
the trailing cold front as it surges into southeast TX. It's not
clear how far southwest convection will develop along the boundary
due to weak low-level convergence, but warm surface temperatures and
steep low-level lapse rates may encourage isolated storms as far
west as SAT by 16/00z. Hail will be the greatest risk with this
secondary development.
..Darrow/Squitieri.. 04/15/2023
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