ACUS11 KWNS 212020
SWOMCD
SPC MCD 212020=20
IAZ000-212145-

Mesoscale Discussion 0875
NWS Storm Prediction Center Norman OK
0320 PM CDT Tue May 21 2024

Areas affected...Southwest/South-Central IA

Concerning...Tornado Watch 277...

Valid 212020Z - 212145Z

The severe weather threat for Tornado Watch 277 continues.

SUMMARY...A localized corridor favorable for strong tornadoes exists
across southwest/south-central Iowa, including Des Moines vicinity.

DISCUSSION...Pair of supercells on the southern end of the line of
storms extending across western IA have recently shown notable
intensification, with rotational velocity recently estimated around
50 to 55 kt within the southernmost cell. Strong southerly flow
exists ahead of this storm, contributing to strong low-level shear,
evidenced by recent 0-500m storm relative-helicity around 200 m2/s2
from DMX VAD. Robust deep-layer shear exists as well, with DMX VAD
sampling 0-6 km bulk shear was over 60 kt. Recent mesoanalysis
estimates effective-layer STP from 3 to 4 downstream. All of these
factors suggest the downstream environment will remain conducive for
supercell persistence. Storm motion for this southernmost storm is
estimated to be northeasterly at around 45 kt, bring it into the Des
Moines vicinity around 2130Z.

..Mosier.. 05/21/2024

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!9mRGYX6QTWJvOxJmAvW3vxoWHWhclLzieAsmf44pICZu6I7v1-D3leif8vDX-niMR0lB4zxXm= rgm2XaozAz2FtGDiuo$ for graphic product...

ATTN...WFO...DMX...OAX...

LAT...LON 40719467 41269501 41659451 41949347 41189288 40719467=20


=3D =3D =3D
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