Alert archive / Michigan / Mesoscale Discussions in 2021
Mesoscale Discussion 1491
The Storm Prediction Center issued this mesoscale discussion at Aug 11, 2021, 7:45 PM EDT for 21 counties in Michigan; Milwaukee County, Racine County, Wisconsin. It was in force for 90 min.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 7:45 PM EDT (23:45 UTC)
- Expired
- Aug 11, 2021, 9:15 PM EDT
- In force
- 90 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 23 counties
Allegan County, MI, Barry County, MI, Calhoun County, MI, Cass County, MI, Clinton County, MI, Eaton County, MI, Gratiot County, MI, Ingham County, MI, Ionia County, MI, Isabella County, MI, Kalamazoo County, MI, Kent County, MI, Mecosta County, MI, Midland County, MI, Montcalm County, MI, Muskegon County, MI, Newaygo County, MI, Oceana County, MI, Ottawa County, MI, Shiawassee County, MI, Van Buren County, MI, Milwaukee County, WI, Racine County, WI
The radar
The Grand Rapids radar (KGRR), 40 km from the middle of the area, began a volume at 23:44 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.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Detroit, MI (KDTX), launched 12:00Z, 11.8 hours before the alert went out and 214 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 106 J/kg
- Mixed-layer CIN
- -290 J/kg
- Mixed-layer LCL
- 1220 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 169 m²/s²
- 0-3 km storm-relative helicity
- 167 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
319
ACUS11 KWNS 112346
SWOMCD
SPC MCD 112345
MIZ000-WIZ000-120115-
Mesoscale Discussion 1491
NWS Storm Prediction Center Norman OK
0645 PM CDT Wed Aug 11 2021
Areas affected...Southern Lake MI into central/southern Lower MI
Concerning...Severe potential...Watch unlikely
Valid 112345Z - 120115Z
Probability of Watch Issuance...20 percent
SUMMARY...Storms will likely increase in coverage this evening,
posing a threat of at least isolated hail and damaging wind gusts.
DISCUSSION...At 2330Z, thunderstorms are increasing in coverage over
southeast WI and southern Lake Michigan/southwest lower MI. These
storms are likely being driven by a rather strong southwesterly
low-level jet and rooted near or just above 850 mb, based on recent
RAP forecast soundings across the region. While effective shear for
storms rooted near 850 mb is relatively weak, steep midlevel lapse
rates may support a localized hail risk with the strongest updrafts.
Also, given that some heating has occurred across southwest lower MI
in the wake of earlier convection and DCAPE is still generally
greater than 1000 J/kg, some risk of damaging wind gusts will also
be present despite the elevated nature of the convection.
Since these elevated storms are expected to remain relatively
disorganized, watch issuance is currently considered unlikely,
though this will be reconsidered if trends indicate storms
developing an organized cold pool and/or becoming rooted closer to
the surface with time.
..Dean/Goss.. 08/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...IWX...GRR...MKX...
LAT...LON 43148801 43718649 43788533 43728442 43018394 42448417
42038517 41908600 42078697 42708793 43148801SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 10, 8:12 PM EDT | Mesoscale Discussion | SPC | Allegan, Barry, Berrien, Branch, Calhoun, Cass and 25 more | 63 min |
| Aug 10, 8:38 PM EDT | Severe Thunderstorm Watch | SPC | Allegan, Barry, Benzie, Berrien, Branch, Calhoun and 31 more | 5 hr |
| Aug 10, 10:57 PM EDT | Mesoscale Discussion | SPC | Alcona, Alpena, Antrim, Arenac, Barry, Bay and 44 more | 93 min |
| Aug 11, 10:52 AM EDT | Mesoscale Discussion | SPC | Berrien, Branch, Calhoun, Cass, Hillsdale, Jackson and 3 more | 83 min |
| Aug 11, 11:50 AM EDT | Severe Thunderstorm Watch | SPC | Allegan, Barry, Berrien, Branch, Calhoun, Cass and 14 more | 4 hr |
| Aug 11, 12:48 PM EDT | Mesoscale Discussion | SPC | Menominee | 117 min |
| Aug 11, 1:17 PM EDT | Tornado Watch | SPC | Delta, Menominee | 8 hr |
| Aug 11, 1:26 PM EDT | Mesoscale Discussion | SPC | Branch, Hillsdale, Kalamazoo, Saint Joseph | 94 min |
| Aug 11, 2:12 PM EDT | Mesoscale Discussion | SPC | Genesee, Huron, Lapeer, Lenawee, Livingston, Macomb and 9 more | 93 min |
| Aug 11, 2:32 PM EDT | Severe Thunderstorm Watch | SPC | Bay, Genesee, Huron, Lapeer, Lenawee, Livingston and 11 more | 4 hr |
| Aug 11, 4:20 PM EDT | Mesoscale Discussion | SPC | Alcona, Alpena, Antrim, Benzie, Cheboygan, Crawford and 13 more | 115 min |
| Aug 11, 4:48 PM EDT | Severe Thunderstorm Watch | SPC | Alcona, Alpena, Antrim, Arenac, Benzie, Charlevoix and 17 more | 3 hr |
| Aug 11, 8:27 AM EDT | Mesoscale Discussion | SPC | Barron, Buffalo, Burnett, Chippewa, Dunn, Eau Claire and 8 more | 2 hr |
| Aug 11, 3:02 PM EDT | Mesoscale Discussion | SPC | Adams, Brown, Calumet, Columbia, Crawford, Dodge and 20 more | 88 min |
| Aug 11, 6:40 PM EDT | Mesoscale Discussion | SPC | Columbia, Dane, Grant, Green, Iowa, Jefferson and 3 more | 95 min |
Nearby
Mesoscale Discussions in Michigan, 2021Mesoscale Discussions in Wisconsin, 2021Every mesoscale discussion in 2021
Sources
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.