Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 231023
SWOMCD
SPC MCD 231023
INZ000-ILZ000-231230-

Mesoscale Discussion 1406
NWS Storm Prediction Center Norman OK
0523 AM CDT Sun Jul 23 2017

Areas affected...Southern IL

Concerning...Severe Thunderstorm Watch 435...

Valid 231023Z - 231230Z

The severe weather threat for Severe Thunderstorm Watch 435
continues.

SUMMARY...The greatest severe-weather threat (damaging winds) will
be near and south of I-70 in southeast IL through 11Z, when it
should be reaching the southern portion of the IL/IN border.

DISCUSSION...At 0955Z, mosaic radar imagery showed a fast-moving
(40-50 kt) band of storms in south-central IL, with the fastest
portion attendant to the middle and northern part of the line in
Effingham County into Clay County.  These storms continue to move
through a moderately unstable airmass (MUCAPE 1500+ J/kg) in
southern IL, while a strong westerly rear-inflow jet is aiding in
the fast storm motion and damaging surface wind gusts.  Meanwhile,
the environment in southwest IN continues to be stabilized as new
storm development persists northeast and atop a cold pool from
earlier convection.  This factor is expected to result in a
deceleration of the southern IL storms as they reach the southern
IL/IN border area around 11Z.  Given the fast forward storm motion,
a locally strong wind gust could occur into southwest IN, though
overall stabilizing trends east into IN suggests a new WW is not
warranted.

..Peters.. 07/23/2017

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

ATTN...WFO...IND...PAH...ILX...LSX...

LAT...LON   37908867 37978879 38478860 38598869 39268877 39258759
            38768750 38198785 37918806 37908867




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