SPC AC 250739

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0239 AM CDT Tue Aug 25 2020

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
   PLAINS INTO THE GREAT LAKES AND NORTHEAST STATES...

   ...SUMMARY...
   Severe storms are possible Thursday from a portion of the northern
   Plains through the Great Lakes and Northeast States. Damaging wind
   and large hail are the main threats. A few tornadoes will also be
   possible over the lower Mississippi Valley region.

   ...Lower Great Lakes through Northeast States...

   Early Thursday morning a warm front will extend from northern NY
   southeast into southern New England. This boundary will move east
   during the day, while a cold front advances southeast through the
   lower Great Lakes reaching the Northeast States by late Thursday
   afternoon. Elevated storms should be ongoing within zone of ascent
   on cool side of the warm front from northern NY into New England.
   Overall severe threat with this activity will probably remain
   limited. In wake of morning storms and the passing warm front, the
   advection of rich low-level moisture with upper 60s F dewpoints and
   diabatic warming should result in moderate instability with
   1500-2500 J/kg MLCAPE possible. Additional storms will likely
   develop along lake breezes and approaching cold front and spread
   southeast through a portion of the Northeast States. This region
   will remain within belt of stronger northwesterly winds aloft with
   40-50 kt effective bulk shear supporting fast-moving organized
   storms including bowing segments and supercells. Have introduced a
   sig area this update, and an upgrade to higher probabilities will
   likely be needed in day 2 updates.  

   ...Northern Plains through Upper Great Lakes...

   Storms are forecast to be ongoing over a portion of the northern
   High Plains early Thursday, but evolution of the morning activity is
   uncertain. A reinforcing surge of cooler dry air will augment
   frontogenetic forcing along pre-existing baroclinic zone from a
   portion of the northern Plains into the Great Lakes where the
   atmosphere will likely become moderately unstable during the
   afternoon. While a capping inversion might inhibit surface-based
   storms over this region much of the day, additional storms will
   likely develop by late afternoon or early evening from SD into
   southern MN and the Great Lakes in association with increasing
   frontogenetic forcing. This region will reside within belt of
   moderate winds aloft with 35-50 k effective bulk shear supportive of
   organized storm structures. Primary threats will be large hail and
   damaging wind from late afternoon into the evening. 

   ...Lower Mississippi Valley region...

   Strong wind fields and large hodographs associated with the remnants
   of Laura will spread through the lower MS Valley region. The risk
   for a few tornadoes will likely persist. A portion of this region
   will likely be upgraded to a SLGT risk in subsequent outlooks.

   ..Dial.. 08/25/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z