ZCZC SPCSWOMCD ALL
ACUS11 KWNS 261947 
SPC MCD 261947 
MIZ000-INZ000-ILZ000-MOZ000-262145-

Mesoscale Discussion 1112
NWS Storm Prediction Center Norman OK
0247 PM CDT Sat Jun 26 2021

Areas affected...Parts of central/southern Lower
Michigan...northwestern Indiana...central Illinois...into east
central Missouri

Concerning...Tornado Watch 321...

Valid 261947Z - 262145Z

The severe weather threat for Tornado Watch 321 continues.

SUMMARY...More substantive thunderstorm intensification is ongoing
and likely to continue through late afternoon.  Stronger storms will
continue to pose a risk for tornadoes, with organizing clusters also
posing a risk for damaging downbursts.  Areas east and southwest of
Tornado Watch 321 are being monitored for the possibility of
additional watches.

DISCUSSION...A remnant convectively generated surface
boundary/deformation zone between a pair of MCV remains the primary
focus for deepening convective development and scattered vigorous
embedded thunderstorm activity.  Boundary layer dewpoints are
increasing through the lower 70s F across interior southern Lower
Michigan, and remain in the mid 70s F southwest of Chicago into the
St. Louis area along this zone, where low-level hodographs also
remain sizable beneath a 30-40 kt south-southwesterly 850 mb jet. 
The primary jet core now appears to be nosing into southern Lower
Michigan, but a secondary core appears to be currently migrating
across/northeast of the St. Louis area.

Despite weak lapse rates, the high boundary-layer  moisture content
appears to be contributing to mixed-layer CAPE of 1500-2000 J/kg. 
Coupled with the strong low-level vertical shear, the environment
appears to be coming increasingly conducive to strengthening
low-level mesocyclones within the stronger storms through late
afternoon.  These may occasionally pose a risk for tornadoes and/or
strong downbursts.

..Kerr.. 06/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DTX...IWX...GRR...LOT...ILX...LSX...

LAT...LON   38819100 40059007 40948873 41378791 41568732 41818658
            41978593 42848501 43268326 42138398 41268580 40588753
            39648943 38529041 38819100 

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