ZCZC SPCSWOMCD ALL
ACUS11 KWNS 102251 
SPC MCD 102251 
ILZ000-WIZ000-IAZ000-110015-

Mesoscale Discussion 1467
NWS Storm Prediction Center Norman OK
0551 PM CDT Tue Aug 10 2021

Areas affected...Portions of Iowa...Illinois and Wisconsin.

Concerning...Severe Thunderstorm Watch 419...420...

Valid 102251Z - 110015Z

The severe weather threat for Severe Thunderstorm Watch 419, 420
continues.

SUMMARY...A well-developed line of thunderstorms will continue to
pose a risk for damaging winds as it tracks east/southeast across
WW419 and WW420.

DISCUSSION...As of 2245 UTC, SPC mesonalysis shows extreme
instability (MLCAPE of 4000-5000 J/kg) is in place with little
remaining convective inhibition ahead of a line of severe
thunderstorms across eastern Iowa, western Illinois and southern
Wisconsin. Within the line, recent radar and satellite trends
indicate a corridor of enhanced wind-damage potential may evolve
across the southern Wisconsin and northern Illinois border region
over the next several hours. Surface obs immediately behind the line
show stronger cold pool development is underway. Greater lift along
the cold pool may contribute to a stronger rear-inflow jet and
bowing out of the line segment with time. This is also corroborated
by several recent reports of wind damage and a measured wind gust of
70 mph in Platteville, WI. Additional damaging wind gusts, some
potentially 70+ mph, appear possible as this segment of the line
continues to the east along the Illinois/Wisconsin border.

Farther south across eastern Iowa, storms have struggled to maintain
intensity likely due to weaker effective shear below 25 kts.
Additional development ahead of the main line has been noted within
the very unstable airmass, and should continue into this evening.
While somewhat less favorable for severe wind gusts given the weaker
vertical shear and limited organization, the additional storm
development will likely reinforce the cold pool associated with
previous convection and support a few damaging wind gusts as it
track to the south and east into northwestern Illinois

..Lyons.. 08/10/2021

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

ATTN...WFO...LOT...MKX...DVN...ARX...

LAT...LON   42029165 42599062 43239045 43479025 43618978 43508869
            43218794 42858784 42328785 41808788 41598922 41229098
            41439144 41859167 42029165 

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