SPC AC 131258

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0758 AM CDT Wed Apr 13 2022

   Valid 131300Z - 141200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF AR/MS/TN/MO/IL/IN/KY...

   ...SUMMARY...
   Numerous severe thunderstorms are expected today across the
   Mid-South and lower/middle Mississippi Valley and Midwest.
   Tornadoes, some of which will be strong, widespread and potentially
   significant damaging thunderstorm winds, and large hail are likely
   especially within the Moderate and Enhanced Risk areas.

   A severe-storm outbreak is expected today into tonight. Widespread
   severe storms are likely across a very broad north-south region from
   the Lower Mississippi Valley and Mid-South into the Midwest, with
   atmospheric ingredients favorable for all severe hazards, including
   potentially significant/intense severe storms.

   ...Mid-South/Lower to Middle Mississippi Valley/Midwest...
   An upper trough, with its axis centered over the High Plains early
   today, will eject northeastward toward the Midwest/Ohio Valley, with
   a pronounced strengthening of mid/high-level jet stream winds
   (80-110 kt) particularly over the Ozarks/Midwest/Ohio Valley. These
   strong winds and related height falls/forcing for ascent will
   overspread a semi-moist boundary layer (low to middle 60s F surface
   dewpoints) across the Midwest ahead of an eastward-moving cold
   front, with more consequential moisture availability (upper 60s F)
   expected across the ArkLaTex/Mid-South/Lower Mississippi Valley,
   where severe/supercell-conducive wind profiles will exist even well
   south of the stronger portions of the polar jet.

   Speaking to early morning airmass characteristics, pre-dawn surface
   analysis in conjunction with 00z and 06z (via PERiLS project)
   upper-air analysis/trends reflect some air mass impacts via a
   persistent MCS and resultant MCV across western Tennessee and nearby
   ArkLaMiss. Observed meso-high and MCS-aftermath dry air in vicinity
   of the ArkLaMiss are expected to decay relatively early today,
   although these factors cast some uncertainty for the spatial details
   of later-day availability of rich moisture. For these reasons, along
   with a considerable amount of upstream early day convection/cloud
   cover, an upward adjustment to the current Moderate Risk category
   does not appear prudent at this time /13z/. That said, regarding the
   early day MCV/lingering outflow, an ample moisture reservoir over
   east Texas (850 mb dewpoints 12+C) is expected to largely replenish
   the broad warm/moist sector into the afternoon (reference 12z
   Shreveport LA observed sounding etc.), which will be beneath a
   notable eastward-extending elevated mixed layer.

   For short-term details across southeast Oklahoma and the ArkLaTex,
   see Mesoscale Discussion 471. Regarding central/southern Missouri
   and western Illinois in the short-term, see Mesoscale Discussion
   472.

   By midday/early afternoon, moderate to strong instability and
   steadily weakening CINH will be in place across Arkansas/Louisiana
   toward the Lower Mississippi Valley, where model forecasts have
   MLCAPE in the 2000 to 3000 J/kg range. Ample deep-layer/low-level
   shear will be favorable for supercells, initially capable of large
   hail and tornadoes. Discrete supercells ahead of the organizing
   squall line will have the potential for strong/intense tornadoes
   including some that are potentially long-track, particularly as the
   low-level jet further strengthens across the region later this
   afternoon into early evening. This corridor of
   stronger/longer-duration tornado concern is focused across the
   Mid-South/ArkLaMiss vicinity. Otherwise, potentially
   widespread/locally significant damaging thunderstorm wind gusts will
   also evolve as the squall line organizes, intensifies, and moves
   eastward with embedded bowing segments, although QLCS-related
   tornadoes can also be expected.

   The damaging wind/tornado risk may linger through the
   late-evening/overnight hours across portions of Mississippi/Alabama
   and southern Louisiana and the Florida Panhandle. This would be via
   a persistence of moist and strong/confluent low-level flow, although
   850 mb winds are forecast to gradually weaken overnight.

   For areas northward into/across Missouri, Illinois, and Indiana, it
   appears likely that storms will increase and intensify initially
   across southern Missouri, as early as this morning in vicinity of
   the outflow-enhanced effective cold front. These storms will pose a
   damaging wind and some severe hail risk especially into the
   afternoon as they organize and race east-northeastward. The
   potential for tornadoes will exist as well, in dual scenarios
   including any pre-squall line supercellular development and within
   an evolving QLCS itself, especially as storms encounter a
   dramatically strengthening south-southwesterly low-level jet (50-60
   kt at 850 mb) across southeast Missouri and areas eastward across
   Illinois/Indiana/Kentucky. Tornadoes and potentially
   widespread/locally significant damaging winds are likely especially
   through the afternoon and early/mid-evening hours.

   ...Northeast States...
   Low-level moistening will occur today in the wake of a
   northward-shifting warm front, with isolated thunderstorm
   development across the region this afternoon expected to be aided by
   a northeastward-moving shortwave trough aside from orographic lift.
   Weak to locally moderate destabilization across central New York
   into central/eastern Pennsylvania may support a few severe storms as
   lapse rates diurnally steepen. A few instances of wind damage and
   hail would be the primary hazards.

   ..Guyer/Smith.. 04/13/2022

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