ZCZC SPCSWOMCD ALL
ACUS11 KWNS 302215 
SPC MCD 302215 
ILZ000-MOZ000-302345-

Mesoscale Discussion 1903
NWS Storm Prediction Center Norman OK
0515 PM CDT Fri Aug 30 2019

Areas affected...Portions of eastern MO into southwestern IL

Concerning...Severe Thunderstorm Watch 629...

Valid 302215Z - 302345Z

The severe weather threat for Severe Thunderstorm Watch 629
continues.

SUMMARY...Isolated severe threat, including the potential for a
brief tornado or two, should continue near and south of the St.
Louis metro through the early evening.

DISCUSSION...A supercell that formed earlier this afternoon along a
surface boundary across eastern MO produced large hail up to 2.5
inches in diameter. This storm has also shown occasional low-level
rotation as it approached the St. Louis metro area over the past
hour or so. Although low-level flow across this region is not overly
strong, it does veer substantially from northeasterly along and just
north of the surface boundary to south-southwesterly at mid levels
per recent VWPs from KLSX. This veering is contributing to around
40-50 kt of effective bulk shear, which will continue to support
organized thunderstorms, including supercells, in the short term.
Around 100-150 m2/s2 of effective SRH should also promote some
potential for low-level rotation within any supercell that can
maintain itself along/near the surface boundary through the early
evening. A isolated, brief tornado remains possible, along with a
large hail and damaging straight-line wind threat. This isolated
severe risk will likely diminish later this evening (generally after
01Z) as the loss of diurnal heating results in a gradually
stabilizing boundary layer and diminishing instability.

..Gleason.. 08/30/2019

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

ATTN...WFO...LSX...

LAT...LON   38219113 38619078 38809034 38978947 38748929 38328930
            38188974 37789024 37349063 37339115 38219113 

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