Mesoscale Discussion 1468

Issued

Aug 10, 2021, 8:12 PM EDT (00:12 UTC)

Expired

Aug 10, 2021, 9:15 PM EDT

In force

63 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

95%

The Grand Rapids radar (KGRR), 31 km from the middle of the area, began a volume at 00:15 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.

• Severe Thunderstorm Watch 421Aug 10, 8:40 PM EDT

654 
ACUS11 KWNS 110012
SWOMCD
SPC MCD 110012 
MIZ000-OHZ000-INZ000-WIZ000-ILZ000-110115-

Mesoscale Discussion 1468
NWS Storm Prediction Center Norman OK
0712 PM CDT Tue Aug 10 2021

Areas affected...Western lower Michigan into northern Indiana and
far northwestern Ohio

Concerning...Severe potential...Watch likely 

Valid 110012Z - 110115Z

Probability of Watch Issuance...95 percent

SUMMARY...A line of severe thunderstorms is expected to cross lake
Michigan and northern Indiana this evening. Damaging wind gusts
appear likely and a new weather watch will be coordinated shortly
for portions of lower Michigan, Indiana and Ohio.

DISCUSSION...As of 0000 UTC regional RADAR imagery showed a
well-developed convective line stretching from KGRB to KLOT.
Numerous reports of wind damage and measured gusts of 50 to 60 mph
have been reported with these storms over the last several hours.
Ongoing within an extremely unstable airmass characterized by MLCAPE
in excess of 4500 J/kg, observational trends and high-resolution
model guidance suggest these storms will continue to pose a risk for
damaging wind gusts this evening as they approach and eventually
cross Lake Michigan. While some weakening is expected across the
lake due to cooler temperatures, the strongly unstable environment
and robust cold pool should allow storms to maintain their current
organization.

Downstream across lower Michigan, Northern Indiana and northwestern
Ohio, a warm front was observed lifting north of Grand Rapids to
near Detroit. South of this front, the airmass remains very unstable
with MLCAPE of 2500-3500 J/kg. As the front continues to move north
this evening, additional destabilization of the airmass is expected.
As storms move back onshore around 0130 to 0200, the strongly
unstable airmass will support a threat for damaging wind gusts. 

A new weather watch will be coordinated shortly for portions of Lake
Michigan, lower Michigan and northern Indiana.

..Lyons/Edwards.. 08/11/2021

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

ATTN...WFO...DTX...APX...IWX...GRR...GRB...LOT...MKX...

LAT...LON   43848775 44218755 44348708 44328629 44328564 44238495
            44038453 43788433 43288413 42528402 41998408 41578428
            41308481 41258572 41178658 41238734 41968767 43058781
            43848775

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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.