SPC AC 050726

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0226 AM CDT Wed Jul 05 2017

   Valid 071200Z - 081200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE OHIO
   VALLEY INTO A PORTION OF THE NORTHEAST STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE CENTRAL HIGH PLAINS...

   ...SUMMARY...
   A few strong to severe storms are possible from the Ohio Valley into
   a portion of the Northeast States Friday. Other strong storms are
   possible over the central High Plains.

   ...Synopsis...

   Synoptic pattern will change little on Friday with upper trough over
   the eastern U.S. expected to undergo further amplification, while a
   ridge persists over the western states. At the surface a cold front
   will continue southeast through the Northeast States and OH Valley
   in association with the amplifying trough. The western extension of
   this boundary will stall across OK/KS. 

   ...Ohio Valley area...

   A moist pre-frontal warm sector with dewpoints in the upper 60s to
   around 70F will reside across the OH Valley into a portion of the
   Northeast States. Destabilization of the boundary layer will result
   in moderate instability in the presence of modest mid-level lapse
   rates. At least a modest increase in deep-layer winds is expected
   with 30-40 kt unidirectional westerly between 2-6 km. A significant
   upper speed max is forecast to move southeast into the Great Lakes
   and Ohio Valley region, but this feature will remain post frontal.
   Nevertheless...storms should redevelop within the weakly capped warm
   sector and along the southeast advancing cold front during the
   afternoon. Vertical shear from 25-35 kt will support primarily
   multicells with storms evolving into clusters and line segments. A
   few strong to damaging wind gusts will be possible through early
   evening. Trends will continue to be monitored for a possible slight
   risk in later updates. 

   ...Central High Plains area...

   As surface high shifts east, winds will return to southeasterly in
   post frontal zone over the central High Plains where dewpoints in
   the 40s to 50s F will advect westward beneath steep mid-level lapse
   rates. This will contribute to a corridor of modest /500-1000 J/kg/
   MLCAPE over the High Plains Friday afternoon. Isolated to widely
   scattered storms should develop over the higher terrain and spread
   southeast into the High Plains where they will pose some risk for
   mainly isolated downburst winds through early evening.

   ..Dial.. 07/05/2017

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