ZCZC SPCSWOMCD ALL
ACUS11 KWNS 271636 
SPC MCD 271636 
INZ000-ILZ000-MOZ000-271900-

Mesoscale Discussion 1119
NWS Storm Prediction Center Norman OK
1136 AM CDT Sun Jun 27 2021

Areas affected...Parts of east central Missouri through central
Illinois and northwestern Indiana

Concerning...Severe potential...Watch unlikely 

Valid 271636Z - 271900Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorms are expected to gradually begin developing
and intensifying through 1-3 PM CDT.  Some may organize into
clusters which could pose a risk for strong to locally severe wind
gusts later this afternoon.  However, it appears unlikely that a
severe weather watch will be needed.

DISCUSSION...Deepening convective development, likely aided by
low-level convergence along a weak frontal zone (associated with
remnant weak large-scale mid-level troughing across the northern
Great Plains/Upper Midwest), is evident near/northwest of the
Greater St. Louis metropolitan area into southeastern portions of
the Greater Chicago area.  Along and south of this front, the
boundary layer remains characterized by seasonably high moisture
content (70s+ F surface dew points...including upper 70s F around
the St. Louis area), and insolation is contributing to CAPE in
excess of 1000 J/kg.  With further heating increasing CAPE up to
1500-2000 J/kg, and weakening remaining inhibition, scattered
thunderstorms are expected to develop and intensify through 18-20Z. 
It is possible that this could by aided by mid/upper forcing
associated with a convectively generated  or enhance perturbation
migrating northeastward from southeastern Kansas/Oklahoma.

Deep-layer mean wind fields and shear along the corridor of
increasing thunderstorm development are rather modest at or below 30
kt, and expected to remain so.  However, this could be sufficient to
support some upscale growing clusters of storms, which could pose a
risk for locally strong downbursts, aided by heavy precipitation
loading, despite generally weak lower/mid tropospheric lapse rates.

..Kerr/Hart.. 06/27/2021

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

ATTN...WFO...IWX...IND...LOT...ILX...LSX...

LAT...LON   39009090 39409063 40398925 40858843 41508756 40618685
            38608985 38369084 39009090 

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