SPC AC 211955

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0255 PM CDT Sat May 21 2022

   Valid 212000Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NEW ENGLAND
   TO SOUTHERN TEXAS...

   ...SUMMARY...
   Scattered severe thunderstorms capable of producing both damaging
   winds and large hail should continue through evening from parts of
   the southern Plains into the lower Ohio Valley, lower Great Lakes
   and Northeast.

   ...20Z Update...
   The primary change made to the Day 1 Outlook was to trim higher
   severe probabilities behind the convective line across the Mid
   Mississippi Valley, as convective overturning has reduced
   surface-based buoyancy. Otherwise, the previous forecast remains on
   track, with scattered to numerous wind/hail producing thunderstorms
   developing ahead of the cold front, from New England to the lower
   Mississippi Valley. Please refer to MCDs 0852-0854 for more
   information. Likewise, damaging gusts/occasionally large hail may
   still accompany ongoing storms across the southeast CONUS (more
   details available via MCDs 0855-0856).

   ..Squitieri.. 05/21/2022

   .PREV DISCUSSION... /ISSUED 1046 AM CDT Sat May 21 2022/

   ...Southern Plains to Northeast...
   A complex and active convective day is anticipated for much of the
   central and eastern US.  Several lines/clusters of strong to severe
   thunderstorms are expected to intensify by mid-afternoon along a
   cold front and associated outflow boundaries from southeast Ontario
   into the Great Lakes region, OH Valley, middle MS Valley and
   southern Plains.  The air mass ahead of the boundaries is quite
   moist with areas of strong daytime heating already occurring.  While
   large scale forcing mechanisms are generally weak along this broad
   corridor, numerous thunderstorms are expected.  Strong instability
   combined with sufficient flow aloft and steep low-level lapse rates
   will result in a risk of locally damaging wind gusts and some hail
   along the entire frontal zone.  Most areas will see multicell storm
   clusters and lines.  However, sufficient low and deep layer shear
   will likely result in a few supercells moving into northern New
   England later today with a slightly higher risk of a tornado or two.
   Please reference recent MCDs #848 and #849 for further short-term
   details.

   ...Gulf Coast states into the Carolinas...
   There is also a broad area of potential for at least isolated strong
   to severe storms over much of the southern and southeastern US
   today.  Wind fields aloft are relatively weak in most places. 
   However, strong heating, rich low-level moisture, and relatively
   cool temperatures aloft will promote robust up/downdrafts capable of
   locally damaging wind gusts and some hail.

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z