Mesoscale Discussion 1620
NWS Storm Prediction Center Norman OK
0530 PM CDT Fri Aug 27 2021
Areas affected...northeast IA
Concerning...Tornado Watch 465...
Valid 272230Z - 272330Z
The severe weather threat for Tornado Watch 465 continues.
SUMMARY...The severe threat in recently issued tornado watch #465
will likely focus primarily in northeast IA during the next 1-2
hours. The risk for supercell-related hazards will include hail,
severe gusts, and possibly a tornado.
DISCUSSION...Visible-satellite imagery shows an outflow boundary
situated west-east across far northeast IA into southwest WI.=20
Temperatures south of the boundary are in the low-mid 80s with mid
70s dewpoints. As a result, a very unstable airmass is located over
the upper MS Valley early this evening. It seems a messy supercell
mode may persist for the next few hours due in part to 1) only weak
forcing but 2) enlargement of the hodograph with a veer-back-veer
wind profile---leading to precipitation seeding near updrafts. RAP
forecast soundings depict this relative limitation in the wind
profile in the upper levels which is only partly observed by the La
Crosse, WI 88D VAD data.
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