Storms moving to the east- Tornado threat will gradually end from the west in the Chicago area later this evening but continue in areas to the east

Mesoscale Discussion 0838
   NWS Storm Prediction Center Norman OK
   0530 PM CDT Mon May 27 2019

   Areas affected...Parts of northeastern Illinois...northern
   Indiana...southern Michigan and western Ohio

   Concerning...Tornado Watch 263...

   Valid 272230Z - 280000Z

   The severe weather threat for Tornado Watch 263 continues.



   SUMMARY...Isolated supercell development may continue, with the
   evolution of an increasingly organized convective system also
   possible through 8-10 PM EDT, accompanied by a continuing risk for
   tornadoes, and increasing potential for damaging wind gusts.  A new
   severe weather watch likely will be needed east/southeast of tornado
   watch 263 within another hour or  two.

   DISCUSSION...A low amplitude short wave trough, with one or two
   embedded MCVs, continues to gradually turn eastward into southern
   portions of the Great Lakes region.  Associated forcing for ascent
   appears to be aiding upscale convective growth across and south of
   the Chicago area, but discrete supercell development persists,
   particularly along the warm frontal zone extending
   east-southeastward across northern Indiana into western Ohio.

   Into the 00-02Z time frame, large-scale lift supported by warm
   advection, in the presence of CAPE on the order of 2000 J/kg, seems
   likely to support considerable further upscale growth.  This
   probably will evolve into an increasingly organized convective
   system in the presence of strong deep layer shear, with increasing
   potential for damaging surface gusts on the leading edge of a
   strengthening surface cold pool.  Low-level shear remains maximized
   along the warm front, and supportive of continuing potential for
   tornadoes in discrete supercells, as well as with potential evolving
   mesovortices along the southeastward advancing gust front.

   While activity will tend to advect eastward in the presence of 40+
   kt westerly deep layer mean ambient flow (toward the Toledo OH
   area), it appears there may also be a tendency to propagate
   southeastward toward the Interstate 70 corridor (near/east of
   Indianapolis IN toward Columbus OH).
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