Mesoscale Discussion 1039

Issued

Jun 20, 2021, 6:56 PM CDT (23:56 UTC)

Expired

Jun 20, 2021, 9:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 294

The Des Moines radar (KDMX), 172 km from the middle of the area, began a volume at 23:54 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

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• Severe Thunderstorm Watch 296Jun 20, 8:10 PM CDT

459 
ACUS11 KWNS 202356
SWOMCD
SPC MCD 202356 
ILZ000-MOZ000-IAZ000-KSZ000-210200-

Mesoscale Discussion 1039
NWS Storm Prediction Center Norman OK
0656 PM CDT Sun Jun 20 2021

Areas affected...Southern Iowa...northern Missouri...northeast
Kansas...and far western Illinois

Concerning...Severe Thunderstorm Watch 294...

Valid 202356Z - 210200Z

The severe weather threat for Severe Thunderstorm Watch 294
continues.

SUMMARY...Strong to severe thunderstorms will continue to pose a
large hail, damaging wind, and some tornado risk into the evening
hours. Southern Iowa and northern Missouri will continue to see the
highest risk in the next 1-2 hours.

DISCUSSION...Discrete to semi-discrete storms continue to develop
and mature along a surface trough and ahead of a cold front from
southern IA to far northeast KS. A few supercells have been noted
with 1-2 inch hail, wind damage, and a tornado reported within the
past 2 hours from this activity. The warm sector ahead of these
storms remains supportive of organized convection with RAP
mesoanalysis estimating upwards of 3000 J/kg MLCAPE and roughly 40
knots of boundary-normal effective bulk shear. While instability
estimates may be slightly high based on the recent 00Z TOP sounding,
the shear estimates appear valid and instability remains sufficient
for severe convection. This includes areas of northern MO and
southeast IA where previously cool/stable outflow has warmed into
the low to mid 80s, minimizing surface-based and mixed-layer
inhibition. 

Discrete to semi-discrete storms remain likely in the near term,
which will maintain the hail/wind and at least a low-end tornado
threat. Storm mode may become more linear with an increasing wind
threat through the late evening as the cold front (noted in KDMX
reflectivity) catches up with the surface trough and increases
forcing for ascent. A downstream watch into eastern MO and perhaps
western IL may be needed if an organized wind threat becomes
apparent.

..Moore.. 06/20/2021

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

ATTN...WFO...ILX...LSX...DVN...DMX...EAX...TOP...

LAT...LON   39509540 40049484 40829403 41589331 42019285 42069241
            41699177 41279111 40619068 39909084 39259134 39039208
            39079311 39009436 39139501 39509540

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.