Mesoscale Discussion 987

Issued

Jun 16, 2021, 11:49 PM CDT (04:49 UTC)

Expired

Jun 17, 2021, 1:15 AM CDT

In force

86 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 275

The Des Moines radar (KDMX), 118 km from the middle of the area, began a volume at 04:53 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

496 
ACUS11 KWNS 170449
SWOMCD
SPC MCD 170449 
IAZ000-MOZ000-170615-

Mesoscale Discussion 0987
NWS Storm Prediction Center Norman OK
1149 PM CDT Wed Jun 16 2021

Areas affected...Southwest IA...Northwest MO

Concerning...Severe Thunderstorm Watch 275...

Valid 170449Z - 170615Z

The severe weather threat for Severe Thunderstorm Watch 275
continues.

SUMMARY...Ongoing convective line will continue to move through
southwest IA, with an attendant threat for hail and damaging wind
gusts.

DISCUSSION...The ongoing convective line has moved across much of
western IA at fairly steady storm motion around 40 kt. KDMX radar
imagery also shows the updrafts keeping pace with the cold pool,
with regional CAPPI data showing relatively stable updraft strength.
These observations suggest the convective line has reached a
favorable cold pool/updraft equilibrium for maintenance/persistence.
Given these trends, expectation is for the ongoing line to continue
for at least the next hour or two. Isolated hail and damaging wind
gusts remain possible.

Thereafter, given the displacement of the line south of the stronger
low to mid-level flow and downstream stabilization of the low-level
air mass, a gradual weakening trend is anticipated. However, some
potential exists for new development over the western portion of the
cold pool to increase/strengthen the cool pool, which would
temporarily increase wind gusts before the system weakens. Given the
uncertainties, the need for a downstream watch remains in question,
but convective trends will be monitored closely.

..Mosier/Guyer.. 06/17/2021

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

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

LAT...LON   41209557 41769530 41879411 41539380 40129352 39769425
            40129519 41209557

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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.