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

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