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).