SPC AC 040546

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1246 AM CDT Sat Jul 04 2020

   Valid 051200Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHERN PLAINS...

   ...SUMMARY...
   Strong to severe thunderstorms are possible across the northern
   Plains Sunday. Isolated severe thunderstorms are also possible
   across the central and southern High Plains as well as southern New
   England.

   ...Northern Plains/northern High Plains...
   An upper ridge is forecast to extend from the Southwest into the
   Upper Midwest early Sunday morning. Northwestern periphery of this
   ridge is expected to dampen throughout the day as a shortwave trough
   progresses eastward/northeastward through the Canadian Prairie
   Provinces and adjacent portions of the northern Plains. Progression
   of this shortwave trough is expected to encourage modest
   southeastward motion of a weak cold front. By 00Z Monday, this front
   will likely extend from central Manitoba southwestward into the far
   western NE Panhandle.

   Warm and moist conditions are anticipated along and south of this
   front. Convective initiation is forecast along the front Sunday
   afternoon where ample low-level moisture and steep mid-level lapse
   rates will support moderate to strong buoyancy. Much of this area
   will be on the southern periphery of the stronger flow aloft,
   limiting vertical shear. Even so, the instability is still expected
   to be strong enough to support updrafts capable of large hail and/or
   damaging wind gusts. Given the weak shear and likelihood for
   outflow-dominant storm structures, storm motion and new storm
   development could be somewhat chaotic. Storms should wane a few
   hours after sunset.

   Back farther west (i.e. across portions of WY and southeast MT),
   upslope flow behind the front will contribute to stronger vertical
   shear Sunday afternoon and evening. Less low-level moisture will
   exist here versus farther east, tempering buoyancy, but the stronger
   vertical shear could still result in a few more organized storm
   structures capable of large hail and strong wind gusts.

   ...Central/Southern High Plains...
   Diurnal thunderstorms may move off the higher terrain during the
   afternoon. Southeasterly surface winds beneath northwesterly flow
   aloft will contribute to moderate shear, which could result in a few
   stronger/more organized storms capable of a strong wind gust or two.

   Additionally, model guidance is in good agreement that a
   convectively induced vorticity maximum will linger near the southern
   CO/KS border, potentially contributing to higher thunderstorm
   coverage over southwest KS and portions of the OK/TX Panhandles.
   Cloud cover associated with this vorticity maximum will limit
   heating, but cool temperatures aloft should help support modest
   instability. A few stronger storms capable of damaging wind gusts
   and/or hail are possible.

   ...Southern New England...
   A cold front is expected to move across the Northeast states Sunday
   afternoon, ahead of a shortwave trough forecast to move through
   later Sunday evening. Instability will likely be modest, but deep
   northwesterly flow aloft will contribute to moderate vertical shear,
   which could support a few bowing multicell segments capable of
   damaging wind gusts.

   ..Mosier.. 07/04/2020

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