SPC AC 110524

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1224 AM CDT Tue Aug 11 2020

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   SOUTH DAKOTA AND NEBRASKA...

   ...SUMMARY...
   Scattered strong/severe convection is expected across portions of
   the Plains from late afternoon into the overnight hours, especially
   across portions of South Dakota and Nebraska. Hail and wind are the
   primary threats. Marginally severe storms are also possible across
   parts of the mid-South and over northern Maine.

   ...South Dakota/Nebraska...

   Early-evening water-vapor imagery depicts a short-wave trough along
   the ID/WY border, shifting east in line with 00z model guidance.
   This feature is forecast to translate east across WY into western
   SD/NE Panhandle by mid-late afternoon. In response, boundary-layer
   moisture that has been shunted south into KS should be drawn
   northwest as lee trough becomes established from the western Black
   Hills into eastern CO. Strong boundary-layer heating is expected
   along the lee trough and forecast soundings suggest convective
   temperatures will be breached around 21-22z. 500mb flow on the order
   of 30-35kt will be maintained at this latitude, along the southern
   edge of the stronger westerlies. As a result, forecast shear appears
   at least somewhat supportive of supercell structures. Latest CAMs
   are reasonably consistent with scattered convection developing ahead
   of the short wave with eastward propagating storms across SD during
   the overnight hours, being maintained by a LLJ and warm advection.

   ...Mid-South...

   High-Plains convection that developed from western KS into the TX
   Panhandle is shifting east across south-central KS/central OK early
   this morning. Remnants of this activity should migrate into eastern
   OK by daybreak. It's possible a weak MCV could evolve along the
   northern extent of this convection, and this may encourage
   downstream convection from southeast OK into AR later in the day.
   Models also suggest a weakness in the mid-level height field will
   evolve over the Ozarks and drift south. This will also prove
   favorable for scattered storms as a reservoir of instability
   currently resides across this region that has not been overturned.

   ...Northern Maine...

   Remnants of Monday's Derecho have progressed across the OH Valley
   and mostly dissipated. However, MVC remains intact over northern
   lower MI and an associated short-wave trough is ejecting toward
   southern ON. This feature should translate north of the
   international border into southwestern QC by 18z. Scattered
   convection should evolve ahead of this short wave and the southern
   extent of this activity could spread across northern Maine. Locally
   strong winds would be the primary threat with these storms.

   ..Darrow/Squitieri.. 08/11/2020

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