SPC AC 160819

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0219 AM CST Fri Feb 16 2018

   Valid 181200Z - 191200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Thunderstorms are forecast to evolve Sunday evening/overnight from
   parts of the southern Plains into the lower Missouri/mid Mississippi
   Valleys.

   ...Synopsis...
   Significant amplification of the upper flow field over the U.S. is
   expected to occur on Sunday, as short-wave troughing digs southeast
   across the western states.  This will allow cyclonic flow to expand
   across roughly the western half of the U.S., while in response,
   downstream ridging will increase across the Southeast, and adjacent
   portions of the Gulf of Mexico, Caribbean, and western Atlantic.

   At the surface/low levels, cold/polar air is forecast to spill
   southward across the Intermountain West and northern Plains with
   time, while a broad zone of southerly to southwesterly low-level
   flow and attendant warm advection increases from the southern Plains
   northeast across the Mississippi and Ohio Valleys and Great Lakes
   region.

   Showers and local/sporadic lightning will occur over parts of the
   West -- mainly the northwestern portions of the country, but at this
   time will not highlight an area for potential for 10% coverage of
   lightning.  Farther east, increasing low-level theta-e advection on
   southerly/southwesterly flow will support increasing potential for
   elevated shower/thunderstorm development -- mainly after dark on
   Sunday.  The most likely zone for thunderstorm activity will extend
   from portions of the southern Plains north-northeast across the
   lower Missouri and mid Mississippi Valley region through 19/12z.

   ..Goss.. 02/16/2018

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