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Mesoscale Discussion 1642
NWS Storm Prediction Center Norman OK
0132 PM CDT Wed Aug 03 2022

Areas affected...western/central Illinois into portions of eastern
Missouri

Concerning...Severe potential...Severe Thunderstorm Watch likely 

Valid 031832Z - 032000Z

Probability of Watch Issuance...80 percent

SUMMARY...Afternoon thunderstorm development along decaying outflow
appears likely this afternoon. Several clusters of strong to severe
thunderstorms capable of severe wind gusts will be possible. A
weather watch is likely.

DISCUSSION...As of 1825 UTC, visible satellite imagery showed
developing cumulus towers along a differential heating/prior outflow
boundary from early morning convective debris across east-central IL
into MO. East of the clouds strong heating (surface temperatures
90F+) are quickly eroding the remaining inhibition. With surface
dewpoints observed above 70 F, 3000-3500 J/kg of MLCAPE will support
vigorous updrafts. Along the southern fringes of stronger
westerlies, vertical shear of 20-25 kt is only marginally supportive
of storm organization. Regardless, the very unstable airmass and
marginal effective shear may result in a few stronger multicell
clusters capable of severe wind gusts and perhaps isolated hail from
this afternoon into this evening. Consolidation of any stronger
clusters that do form may result in a locally greater risk for
severe wind gusts given the magnitude of buoyancy though this is
uncertain. 

The highest confidence in strong/severe storm coverage at the moment
is across western portions of IL where CI is already underway.
Additional development seems likely over the next hour as remaining
inhibition is quite limited from SPC mesoanalysis. Farther south and
west into MO, a couple more hours of heating may be required to
support free convection given the weaker forcing for ascent and
greater cloud cover. While it remains somewhat uncertain when the
severe risk may increase, convective trends will be monitored for a
likely weather watch.

..Lyons/Grams.. 08/03/2022

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

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

LAT...LON   39538874 39128929 38838971 38179060 38039100 37989144
            38019188 38199227 38589233 39079232 39489214 39649202
            40199103 40499044 40719001 40868965 40928925 40928892
            40698846 40538833 40308833 40128832 39858837 39538874