Mesoscale Discussion 1469

Issued

Aug 10, 2021, 10:57 PM EDT (02:57 UTC)

Expired

Aug 11, 2021, 12:30 AM EDT

In force

93 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 421

The Grand Rapids radar (KGRR), 52 km from the middle of the area, began a volume at 02:59 UTC, the scan nearest the moment this went out.

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417 
ACUS11 KWNS 110258
SWOMCD
SPC MCD 110257 
MIZ000-OHZ000-INZ000-110430-

Mesoscale Discussion 1469
NWS Storm Prediction Center Norman OK
0957 PM CDT Tue Aug 10 2021

Areas affected...Much of lower Michigan and adjacent portions of
northern Indiana and northwest Ohio

Concerning...Severe Thunderstorm Watch 421...

Valid 110257Z - 110430Z

The severe weather threat for Severe Thunderstorm Watch 421
continues.

SUMMARY...A generally weakening line of thunderstorms may continue
to be accompanied by strong to locally severe wind gusts across much
of the remainder of lower Michigan and adjacent portions of northern
Indiana and northwestern Ohio by 1-2 AM EDT.  It is not yet certain
that this will require an additional severe weather watch across
eastern lower Michigan and northwestern Ohio, but trends are being
monitored for this possibility.

DISCUSSION...Substantial weakening has occurred to the ongoing
convective system as it crossed Lake Michigan, and the temperature
differential across the leading edge of the eastward advancing
surface outflow is diminishing in a less strongly heated and slowly
cooling boundary layer across lower Michigan.  However, at least a
narrow corridor of mid/upper 70s F surface dew points is returning
northward ahead of line, across the Battle Creek and Lansing
vicinities.  And there are still areas of 50+ kt rear inflow still
evident.  

At its current 45-50 kt forward propagation, the convective system,
or its remnants, will overspread much of the remainder of lower
Michigan and adjacent northwestern Ohio by 05-06Z.  It remains
unclear whether there will be significant re-intensification of
convection, but the best chance for this may be along a zone of
enhanced low-level warm advection preceding the convection, roughly
across the Houghton Lake, Saginaw, Flint vicinities.  Regardless,
the gust front may remain capable of producing strong to locally
severe wind gusts.

..Kerr.. 08/11/2021

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

ATTN...WFO...CLE...DTX...APX...IWX...GRR...LOT...

LAT...LON   40958739 41368613 42328530 43588562 44598578 45328553
            45508358 44578267 43478246 42078247 41088378 40728590
            40958739

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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.