SPC AC 240734

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0134 AM CST Fri Dec 24 2021

   Valid 261200Z - 271200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Thunderstorms are expected along the West Coast from Washington to
   northern California through the day Sunday with isolated lighting
   possible in portions of Missouri Sunday evening and Sunday night.

   ...Synopsis...
   A persistent upper-level ridge will continue to strengthen off the
   Southeast US coast on Sunday. A mid-level shortwave trough will move
   from the Four Corners Region Sunday morning to the Great Lakes by
   Sunday night. As it moves northeast, the trough will deamplify as it
   moves into the building heights across the eastern CONUS. A strong
   lee cyclone is expected to develop on Sunday morning in eastern
   Colorado. However, as the upper-level system becomes less
   pronounced, this surface low will start to fill as it moves
   northeast through the day and into the overnight hours.

   Strengthening southerly flow is forecast across the warm sector as
   the pressure gradient tightens in response to the strengthening lee
   cyclone. This will bring an unseasonably moist airmass northward
   with low 60s dewpoints as far north as southern Illinois/Indiana by
   12Z Monday. Despite this greater low-level moisture, storms are not
   expected across most of the warm sector due to a strong capping
   inversion and a lack of stronger forcing for ascent to break this
   cap. Enough weakening of the cap may occur in portions of Missouri
   Sunday evening and Sunday night for isolated storms, but instability
   should remain too weak to support a severe threat.

   ..Bentley.. 12/24/2021

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