Mesoscale Discussion 1444

Issued

Aug 8, 2021, 3:00 PM CDT (20:00 UTC)

Expired

Aug 8, 2021, 5:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 415

The St Louis radar (KLSX), 1 km from the middle of the area, began a volume at 19:59 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

160 
ACUS11 KWNS 082000
SWOMCD
SPC MCD 082000 
ILZ000-MOZ000-082200-

Mesoscale Discussion 1444
NWS Storm Prediction Center Norman OK
0300 PM CDT Sun Aug 08 2021

Areas affected...Portions of southern/eastern MO into
western/central IL

Concerning...Severe Thunderstorm Watch 415...

Valid 082000Z - 082200Z

The severe weather threat for Severe Thunderstorm Watch 415
continues.

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
possible.

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
cores.

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.

..Gleason.. 08/08/2021

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

ATTN...WFO...PAH...LOT...ILX...LSX...DVN...SGF...

LAT...LON   36819258 37269205 38069145 38829164 39629220 40439096
            40958959 40998863 40668836 39748838 38508872 36589027
            36579236 36819258

Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Missouri, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.