SPC AC 050601

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0101 AM CDT Fri Jun 05 2020

   Valid 051200Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
   THE MIDDLE TO LOWER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Strong to locally severe thunderstorms are possible Friday across
   the middle to lower Mississippi Valley, the Northern Rockies and
   adjacent plains, eastern Wyoming and the Mid-Atlantic states as well
   as a portion of the Great Basin. Isolated damaging wind and hail are
   the main threats.

   ...Middle to lower Mississippi Valley region...

   Cluster of storms now moving through southeast NE and northeast KS
   will continue southeast into northern MO into the early morning,
   while likely undergoing some weakening. A reservoir of strong
   instability  persists from eastern KS into MO and AR where the
   eastern periphery of the elevated mixed layer plume resides above
   rich low-level moisture. Diabatic warming should support up to 4000
   J/kg MLCAPE this afternoon. Tendency will be for upper ridge to
   build northeastward during the day. However, a remnant MCV as well
   as an outflow boundary from ongoing storms will likely be somewhere
   over northern or central MO by 12Z. This will support redevelopment
   of storms southward along instability gradient through southern MO
   and into the lower MS Valley region. Storms will likely intensify as
   the boundary layer destabilizes with most CAMS supporting evolution
   into an MCS as activity moves southward during the day and into the
   early evening. Damaging wind will be the main threat.

   ...Northern Rockies and adjacent Plains...

   Upper ridge will continue to build northward through the High
   Plains. However, a belt of stronger westerlies will persist over the
   Northern Rockies downstream from an approaching upper trough. While
   low-level moisture will be somewhat limited, steep lapse rates and
   diabatic warming will contribute to 500-1500 J/kg MLCAPE. A series
   of vorticity maxima will move northeast through this region along
   northwestern periphery of the building ridge, and at least isolated
   storms are expected to develop over the higher terrain and spread
   northeast into the adjacent Plains. Vertical wind profiles with 40+
   kt effective bulk shear will support potential for a few high-based
   supercells with large hail and locally strong to damaging wind gusts
   the main threats from late afternoon into mid evening. Due to
   potential for limited severe storm coverage, will maintain MRGL risk
   category, but a SLGT might be required in later updates.

   ...Middle Atlantic States...

   Storms will likely once again develop over the higher terrain and
   spread east through the Middle Atlantic states where moderate
   instability will reside. A pronounced MCV currently moving through
   KY will emerge across VA during peak heating, and may result in
   greater storm coverage and possibly slightly more favorable wind
   profiles for organized multicells. Primary threat will be locally
   strong to damaging wind gusts during the afternoon and early
   evening. 

   ...Great Basin...

   Middle to upper winds will strengthen over the Great Basin just
   downstream from a shortwave trough that will reach southern CA
   during the afternoon. Low-level moisture will remain limited, but
   diabatic warming and steep lapse rates will result in up to 300 J/kg
   MLCAPE. Shallow high-based storms are expected to develop by late
   afternoon and spread northward through this region. Deep inverted-V
   profiles with near dry adiabatic lapse rates through 500 mb will
   support potential for downburst winds.

   ..Dial/Nauslar.. 06/05/2020

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