Mesoscale Discussion regarding Severe Thunderstorm Watch
Mesoscale Discussion 1787
NWS Storm Prediction Center Norman OK
0740 AM CDT Sun Aug 18 2019
Areas affected...southeast Wisconsin...
northeast Illinois...northwest Indiana
...and southwest Michigan
Concerning...Severe Thunderstorm Watch 597...
Valid 181240Z - 181445Z
The severe weather threat for Severe Thunderstorm Watch 597
SUMMARY...Thunderstorms continue this morning across the region.
Moderate instability and sufficient shear should continue to support
a severe threat this morning.
DISCUSSION...Initial line of thunderstorms has weakened considerably
this morning as increasing precipitation ahead of the line --
stemming from thunderstorms that developed south-southwest of
Chicago -- has acted to stabilize the airmass across north-central
Illinois and southern Wisconsin. The strongest thunderstorm cluster
from this original band of storms is currently located across
southeast Wisconsin and will have the potential to pose a severe
threat for another couple hours before moving east over Lake
As previously mentioned, additional thunderstorms developed to the
south-southwest of Chicago, ahead of the original line of storms.
These thunderstorms are within a better severe thunderstorm
environment than those to the north given less convective coverage
allowing most-unstable CAPE values to approach 2000 J/kg, and thus
have a greater potential to pose a severe wind or hail threat. At
present, these storms will move across the greater Chicago metro
over the next 1-2 hours, with hail and wind threats likely. These
storms will continue east-northeast through the morning, eventually
moving over Lake Michigan.