SPC AC 170530

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 PM CST Sat Feb 16 2019

   Valid 181200Z - 191200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk of severe thunderstorms appears negligible across the U.S.
   Monday through Monday night.

   ...Discussion...
   Models continue to indicate that one branch of split westerlies
   emanating from the mid-latitude Pacific will undergo at least some
   amplification across the U.S. during this period.  Within the base
   of larger-scale mid-level troughing inland of the Pacific coast,
   another in a series of digging short wave impulses is forecast to
   progress across the Southwestern international border area, before
   gradually turning eastward/northeastward toward the southern U.S.
   High Plains by late Monday night.

   Downstream, it appears that short wave ridging within the
   mid-latitude westerlies will build in phase with the subtropical
   stream, across the lower Plains into the lower Ohio and Tennessee
   Valleys.  This is on the northwestern periphery of a subtropical
   ridge centered near/east of the Bahamas, which is forecast to remain
   prominent through this period.

   Models indicate that increasing mid-level confluence, between the
   building ridge and a digging trough within a branch of westerlies to
   the north, will support the southeastward development of a center of
   expansive cold surface ridging across the northern Plains through
   southern portions of the Great Lakes region.  Along the
   quasi-stationary shallow southwestern periphery of this air mass, it
   appears that a warming and moistening southerly return flow off the
   western Gulf of Mexico will contribute to a gradual erosion of this
   air mass near coastal areas.  

   Farther inland, as the return flow strengthens Monday night
   (including to 30-50 kt around 850 mb), an east-west zone of
   steepening isentropic ascent, near the leading edge of the more
   substantive elevated moisture return, is expected to become the
   focus for increasing thunderstorm development.  It appears that this
   may be associated with CAPE on the order of 250-500 J/kg, though
   continuing elevated moisture return and steepening mid-level lapse
   rates may contribute to increasing CAPE in its wake (to its  south).
   However, the higher potential instability may coincide with
   increasing mid-level inhibition associated with warming aloft.  As a
   result, while some hail may be possible in the stronger storms, the
   potential for severe hail currently seems negligible.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:  <2%     - None
   Wind:     <5%     - None
   Hail:     <5%     - None

   ..Kerr.. 02/17/2019

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z