SPC AC 221732

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1232 PM CDT Fri May 22 2020

   Valid 231200Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
   DAKOTAS AND NEBRASKA...AND FROM WEST TEXAS INTO SOUTHWEST
   OKLAHOMA...

   ...SUMMARY...
   Severe thunderstorms producing damaging hail and wind are likely
   across parts of the Dakotas and Nebraska Saturday afternoon and
   evening. Scattered strong top severe storms are possible over much
   of west Texas. Isolated strong to marginally severe storms are
   possible over much of northern Illinois and into neighboring states.

   ...Synopsis...
   An upper trough will remain over much of the West, with an upper
   high over the Southeast. A weak shortwave trough will top the ridge
   over the Great Lakes region, with a warm front lifting north across
   IA/IL/IN/OH.

   To the west, a vast area of moisture and strong instability will
   exist over the Plains. Low pressure will develop over eastern CO,
   with a dryline from southwest KS into west TX. To the north, a
   surface/inverted trough will extend from central ND into eastern WY.
   The best area for large-scale lift will be near the northern
   boundaries, as a shortwave trough moves from WY into the Dakotas
   late.

   ...West TX into southwest OK...
   A large area of very strong instability will develop with heating,
   beneath weak southwest winds aloft. Mid to upper 60s dewpoints will
   be common east of the dryline from southwest KS into west TX, with
   relatively cool 500 mb temperatures of -11 to 12 C. Capping will be
   a primary concern regarding storm coverage on Saturday.
   Boundary-layer mixing near the dryline may initiate at least
   isolated storms capable of large hail and perhaps damaging winds
   should larger clusters form. Various models are uncertain regarding
   the best areas for initiation and ultimate coverage, but degree of
   instability supports a conditional Slight.

   ...NE/SD/ND region...
   Storms are expected to form relatively early in the day near the
   front, from the Black Hills into western ND. The early initiation as
   well as modest winds aloft suggest clusters of storms may quickly
   form, and possibly an MCS later in the day. Both damaging wind and
   large hail will be possible. 

   Farther south into western NE, eastern WY and northeast CO, wind
   profiles are more favorable for supercells, but capping will be a
   concern. Steep lapse rates as well as veering winds with height will
   conditionally favor supercells, perhaps with localized damaging hail
   and a brief tornado. 

   Storms will then proceed eastward across SD and NE overnight,
   supported by a 30-40 kt low level jet, with continued damaging wind
   threat.

   ...Northern IL and surrounding areas...
   As the warm front lifts north, 1000-1500 J/kg MLCAPE is forecast to
   develop from eastern IA into IL. Wind profiles near the warm front
   show between 100-200 m2/s2 effective SRH, which when combined with
   the moist air mass may support a brief tornado. Storms are likely to
   initiation over eastern IA into northern IL, where heating will
   occur near the convergence zone, then translate east/northeast
   toward southern Lake Michigan. In addition, damaging wind gusts or
   marginal hail will be possible, depending on storm mode which may be
   mixed. A small Slight Risk is possible in later outlooks depending
   on expected storm coverage.

   ..Jewell.. 05/22/2020

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