Mesoscale Discussion 1636

Issued

Aug 28, 2021, 9:57 PM CDT (02:57 UTC)

Expired

Aug 28, 2021, 11:00 PM CDT

In force

63 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Des Moines radar (KDMX), 115 km from the middle of the area, began a volume at 02:59 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.

349 
ACUS11 KWNS 290257
SWOMCD
SPC MCD 290257 
IAZ000-MNZ000-NEZ000-290400-

Mesoscale Discussion 1636
NWS Storm Prediction Center Norman OK
0957 PM CDT Sat Aug 28 2021

Areas affected...eastern NE...western and north-central IA

Concerning...Severe potential...Watch unlikely 

Valid 290257Z - 290400Z

Probability of Watch Issuance...20 percent

SUMMARY...A couple of linear clusters will likely consolidate
further into a continuous squall line from southern MN southwestward
into eastern NE during the next hour.  Intensity of gusts will
probably lessen with time concurrent with the decreasing spatial
coverage of severe/damaging gusts.

DISCUSSION...Radar mosaic at 955pm shows a strong to severe storm
cluster over southwest MN into northwest IA and a separate linear
cluster of eastern NE.  The Norfolk, NE ASOS measured a 53-kt gust
at 902pm.  As a cold front continues to sweep southeast as a
mid-level shortwave trough approaches, storm organization in the
form of a squall line will likely continue into the overnight across
western and into central IA.  Despite the presence of rich low-level
moisture (lower 70s dewpoints), cooling in the boundary layer will
result in increased convective inhibition and weakening buoyancy
with time.  Therefore, it seems likely the squall line will
consolidate into a continuous band of storms but the potential for
severe/damaging gusts will gradually diminish.  Current expectation
is the threat for isolated to widely scattered severe gusts to
continue over eastern NE and far northwest IA for the next hour or
so, but for the propensity for these gusts to become more isolated
as this activity moves farther east and closer to midnight.

..Smith/Guyer.. 08/29/2021

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

ATTN...WFO...ARX...MPX...DMX...FSD...OAX...

LAT...LON   41479685 43469472 43599321 43199298 42689317 41259524
            41179622 41479685

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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.