Mesoscale Discussion 1485

Issued

Aug 11, 2021, 4:20 PM EDT (20:20 UTC)

Expired

Aug 11, 2021, 6:15 PM EDT

In force

115 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

Counties Alcona County, MI, Alpena County, MI, Antrim County, MI, Benzie County, MI, Cheboygan County, MI, Crawford County, MI, Emmet County, MI, Grand Traverse County, MI, Iosco County, MI, Kalkaska County, MI, Manistee County, MI, Missaukee County, MI, Montmorency County, MI, Ogemaw County, MI, Oscoda County, MI, Otsego County, MI, Presque Isle County, MI, Roscommon County, MI, Wexford County, MI

The NCL Michigan radar (KAPX), 9 km from the middle of the area, began a volume at 20:23 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 428Aug 11, 4:40 PM EDT

885 
ACUS11 KWNS 112021
SWOMCD
SPC MCD 112020 
MIZ000-112215-

Mesoscale Discussion 1485
NWS Storm Prediction Center Norman OK
0320 PM CDT Wed Aug 11 2021

Areas affected...Portions of northern Lower MI

Concerning...Severe potential...Watch likely 

Valid 112020Z - 112215Z

Probability of Watch Issuance...80 percent

SUMMARY...The threat for scattered damaging wind gusts and perhaps
isolated tornadoes should increase this afternoon. Watch issuance is
likely.

DISCUSSION...Supercells that formed earlier this afternoon over
north-central WI have recently begun to grow upscale into a cluster
as they move over northern Lake Michigan. A separate cluster ongoing
over the eastern U.P. of MI should continue moving eastward, mainly
across Lake Huron and southern Ontario. The airmass across much of
northern Lower MI was unaffected by a convective cluster that
occurred further south today, with surface temperatures recently
warming into the at least low to mid 80s across northern Lower MI.
The presence of rich low-level moisture and modestly steepened
mid-level lapse rates are contributing to around 2000-2500 J/kg of
MLCAPE. 35-45 kt of deep-layer shear associated with an upper trough
and related west-southwesterly mid-level jet will likely continue to
support storm organization as the northeastern WI cluster moves
eastward over the next couple of hours. Given the mainly linear mode
expected, scattered damaging wind gusts should be the main threat.
Around 100 m2/s2 of 0-1 km SRH may also support an isolated/brief
tornado threat as well. With expectations for an increasing severe
threat through the remainder of the afternoon, watch issuance is
likely in the next hour or so.

..Gleason/Thompson.. 08/11/2021

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

ATTN...WFO...APX...

LAT...LON   44218639 44788631 45498543 45848477 45828364 45358257
            44218231 44218639

Mesoscale Discussions in Michigan, 2021Every mesoscale discussion in 2021

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.