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Mesoscale Discussion 1703
NWS Storm Prediction Center Norman OK
1251 PM CDT Sat Aug 20 2022

Areas affected...southeastern Iowa into west central/central
Illinois

Concerning...Severe potential...Watch possible 

Valid 201751Z - 202015Z

Probability of Watch Issuance...40 percent

SUMMARY...Widely scattered strong storms appear likely to develop
through late afternoon and may pose a risk for primarily marginally
severe hail and locally damaging surface gusts.  It is not certain
that a severe weather watch will be needed, but trends will continue
to be monitored.

DISCUSSION...Moderately large mixed-layer CAPE (in excess of 1000
J/kg) appears to be developing to the south-southeast of a broad,
weak surface cyclone centered over east central Iowa.  This is
occurring beneath a residual pocket of colder mid-level air, in the
wake of one short wave impulse pivoting northeastward into
southwestern portions of the Great Lakes region and ahead of a
trailing impulse digging across Iowa.

Southwesterly to west-southwesterly flow in the 850-500 mb layer
across the destabilizing environment is on the order of 20-30+ kt,
and may still be marginally sufficient to support occasional
supercell structures.  Scattered thunderstorm development is already
underway, and a gradual further increase and intensification of
storms seems probable through the remainder of the afternoon, in
response to additional daytime heating and large-scale forcing for
ascent.  

Ambient vertical vorticity near and within a corridor
south-southeast of the surface low might contribute to some risk for
a brief, weak tornado in stronger cells.  However, low-level
hodographs are generally small, and the more prominent potential
convective hazards appear to be marginally severe hail and locally
strong surface gusts.

..Kerr/Bunting.. 08/20/2022

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

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

LAT...LON   39859109 40989151 41899108 41728963 40288765 39478820
            39188905 39199065 39859109