000
ACUS01 KWNS 310613
SWODY1
SPC AC 310612

Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0112 AM CDT Fri Mar 31 2023

Valid 311200Z - 011200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID MISSISSIPPI VALLEY/MIDWEST AND LOWER MISSISSIPPI
VALLEY...

CORRECTED FOR MISPLACED LABEL

...SUMMARY...
Intense and widespread severe thunderstorms are expected this
afternoon into the overnight hours across portions of the Middle
Mississippi Valley and Mid-South vicinity, eastward to the Lower
Ohio and Tennessee Valleys. Intense, damaging gusts and several
tornadoes (some strong and long-track) are expected.

...Discussion...

Strong, dynamic upper low will begin to deepen early in the period
as it tracks across the central Plains into the Midwest Friday
evening. This feature will encourage a pronounced surface low to
eject into southeast NE by sunrise Friday, then into lower MI by the
end of the period. Significant moisture return ahead of the
associated cold front will lead to an air mass supportive of severe
thunderstorms from the mid MS Valley/Midwest into the lower MS
Valley.

...Mid-MS Valley/Midwest Vicinity...

Early this morning, a strong upper trough is shifting across western
WY/Four Corners region. An upper low should evolve over the central
Plains by late morning with further deepening expected as the low
tracks into the mid MO Valley by early evening. Latest model
guidance suggests a 500mb speed max will increase to near 110kt as
it translates across MO into the OH Valley during the latter half of
the period. As a result, intense 12hr height falls, on the order of
270-300m, will spread across the mid MS Valley/Midwest which should
encourage the aforementioned surface low to deepen as it matures
over northeast IA/southwest WI.

Strong low-level warm advection is currently aiding a corridor of
elevated convection from northeast NE across northern IA,
along/north of a stationary front draped across this region. Latest
thinking is much of the warm sector should remain convective-free
through late morning until leading edge of stronger forcing spreads
east in conjunction with rapid boundary-layer heating ahead of the
cold front. Steep low-level lapse rate plume should develop across
the central Plains early then spread/develop east-northeast across
MO into portions of IA ahead of the front. Forecast soundings
suggest convective temperatures will be breached by 18z immediately
ahead of the low/front. Scattered supercells should develop quickly
thereafter, tracking quickly northeast in response to the
fast-moving upper trough/speed max. Discrete supercells should be
the initial storm mode with very large hail expected. With time,
strong forcing may lead to line segment and clusters. Strong shear
will support long-lived updrafts. In addition to very large hail,
tornadoes can be expected (a few strong) with these storms,
especially prior to any line segment evolution.

While the more concentrated storms should be noted across
IA/northern MO into northwest IL, there is concern for more isolated
long-track supercells across central MO into IL. All hazards can be
expected with these storms.

...Lower MS Valley...

A secondary corridor of concentrated convection is expected to
evolve ahead of the front across the lower MS Valley. Early-day
mid-level speed max that races across northern OK into MO will allow
the front to surge into southern MO, arcing across the Arklatex by
late afternoon. Surface dew points have risen into the mid 60s
across northeast TX/western LA early this morning. This air mass
will easily advance across AR into western KY prior to convective
initiation. As a result, SBCAPE should be on the order of 2000 J/kg
with very strong sfc-6km shear and low-level SRH. Any supercells
that evolve within this air mass will do so within an environment
that favors long-lived updrafts and strong tornadoes. Upscale growth
into a QLCS is expected during the latter half of the period. Severe
threat should spread east across the northern Gulf States Friday
night.

..Darrow/Thornton.. 03/31/2023

$$