SPC AC 061732

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1232 PM CDT Tue Apr 06 2021

   Valid 071200Z - 081200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS A PORTION
   OF THE LOWER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are expected across the lower
   Mississippi Valley with other isolated severe storms possible
   farther north over the middle Mississippi Valley.

   ...Lower Mississippi Valley region...

   Shortwave trough now moving through the central Rockies will
   continue east southeast through the southern Plains and lower to mid
   MS Valley Wednesday. Partially modified Gulf Air with low to mid 60s
   F dewpoints will advect northward along a strengthening southerly
   low-level jet, contributing to a corridor of 1000-1500 J/kg MLCAPE.
   Widespread low clouds are expected in the warm sector which will
   limit boundary layer destabilization to some degree. Thunderstorms
   are expected to develop by mid day along and just ahead of a Pacific
   cold front accompanying the shortwave trough from central MO
   southward through AR and northeast TX. Mixed storm modes are
   expected, and vertical wind profiles with 50+ kt effective bulk
   shear will support the potential for organized storms with both line
   segments and some supercell structures. Hodograph size will increase
   as the low-level jet strengthens with up to 300 m2/s2 storm relative
   helicity supportive of low-level mesocyclones and potential for a
   few tornadoes, especially across the lower MS Valley during the
   afternoon and early evening. However, the degree and extent of the
   tornado threat will depend on whether or not sufficient boundary
   layer destabilization can occur given likelihood of widespread low
   clouds in warms sector where forecast soundings exhibit poor
   low-level lapse rates. Some severe threat, mainly in the form of
   damaging wind will continue into the overnight across a portion of
   the lower MS Valley. An enhanced risk for severe storms might be
   introduced for a portion of this region in day 1 updates.

   ...Middle MS Valley...

   Scattered showers and thunderstorms will likely continue through the
   morning across parts of MO/IA and thereby limit greater instability
   from developing over the area. However, a rejuvenation to storms is
   expected during the afternoon near the surface low and possibly
   farther east ahead of residual decaying convection near the MS
   River. Uncertainty largely related to instability will seemingly
   limit the overall severe threat.  Nonetheless, weak instability
   coupled with deep-layer shear sufficient for organized thunderstorms
   will conditionally support a marginal severe risk for storms during
   the day. Activity will likely weaken by the early evening.

   ..Dial.. 04/06/2021

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