Mesoscale Outlook indicates Severe storm watch likely early this afternoon south and east of Chicago

Areas affected…East-central IL…West-central IN (see highlighted map)

Concerning…Severe potential…Severe Thunderstorm Watch likely

Valid 071719Z – 071815Z

Probability of Watch Issuance…80 percent

SUMMARY…Thunderstorm coverage is expected to increase across
east-central IL and west-central IN. Some of these storms will
likely be severe and a watch will be needed across portions of
region.

DISCUSSION…Recent surface analysis reveals numerous boundaries
across the region. The most prominent in terms of convective
development is the southwestward progressing outflow boundary
extending from Cook (in far northeast IL) county southeastward into
central IN and then eastward into central OH. Several strong/severe
storms developed quickly along this boundary in Lake and Porter
counties. Intensity of these storms appears to have peaked but
additional cellular development is possible along this outflow
boundary with the thermodynamic and kinematic environment supportive
of strong updrafts capable of hail and damaging downburst winds.
Another surface boundary in the region is the pre-frontal trough
extending from Cook county southwestward to just south of PIA and
continuing southeastward into northeast MO. Development has occurred
along this boundary in Grundy county with additional development
possible ahead of this boundary across east-central IL where
dewpoints in the 70s and cooling mid-level temperatures have
resulted in no convective inhibition and MLCAPE around 2000 J/kg.

Overall, thunderstorm coverage is expected to increase in the area
between the two boundaries mentioned with some of these storms
capable of large hail and damaging wind gusts. A watch will likely
be needed to cover this area.