Mesoscale Discussion 1444
NWS Storm Prediction Center Norman OK
0300 PM CDT Sun Aug 08 2021
Areas affected...Portions of southern/eastern MO into
Concerning...Severe Thunderstorm Watch 415...
Valid 082000Z - 082200Z
The severe weather threat for Severe Thunderstorm Watch 415
SUMMARY...Loosely organized storms capable of producing mainly
scattered damaging winds should continue moving east-northeastward
this afternoon. Downstream watch issuance into central Illinois is
DISCUSSION...Storms have increased in coverage across
central/eastern MO this afternoon, but have struggled to intensify
so far. This may be due to modest deep-layer shear (25-30 kt) and
poor mid-level lapse rates limiting updraft strength and
organization. Regardless, low-level lapse rates ahead of the ongoing
loosely organized cluster continue to steepen with diurnal heating.
Strong to damaging wind gusts should be the primary severe threat in
the short term as this activity moves across eastern MO and the St.
Louis metro over the next hour or two. Isolated, marginally severe
hail also remains a possibility with any of the stronger embedded
Farther north into central IL, isolated storms have developed on
what appears to be an outflow boundary associated with an MCV now
moving into western WI. This convection is occurring in environment characterized by moderate instability (MLCAPE 2000-2500 J/kg), but
weak effective bulk shear (25 kt or less). Although an isolated
strong wind gust may occur with these storms in the short term, a
slightly better chance for organized severe storms may occur later
this afternoon as the cluster in eastern MO moves into western and
perhaps parts of central IL. At this point, the need for a
downstream watch into central IL to account for possible damaging
winds remains unclear, but trends will continue to be monitored.
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