Alert archive / Michigan / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 428
The Storm Prediction Center issued this severe thunderstorm watch at Aug 11, 2021, 4:48 PM EDT for 23 counties in Michigan. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 4:48 PM EDT (20:48 UTC)
- Expired
- Aug 11, 2021, 7:58 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 23 counties
Alcona County, MI, Alpena County, MI, Antrim County, MI, Arenac County, MI, Benzie County, MI, Charlevoix County, MI, Cheboygan County, MI, Crawford County, MI, Emmet County, MI, Gladwin County, MI, Grand Traverse County, MI, Iosco County, MI, Kalkaska County, MI, Leelanau 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 radar
The NCL Michigan radar (KAPX), 23 km from the middle of the area, began a volume at 20:48 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 4:54 PM EDT | Severe Thunderstorm Warning | APX | Cheboygan | 51 min |
| Aug 11, 5:00 PM EDT | Severe Thunderstorm Warning | APX | Emmet | 18 min |
| Aug 11, 5:24 PM EDT | Severe Thunderstorm Warning | APX | Charlevoix, Cheboygan, Emmet | 36 min |
| Aug 11, 5:30 PM EDT | Severe Thunderstorm Warning | APX | Antrim, Benzie, Grand Traverse, Kalkaska, Leelanau | 45 min |
| Aug 11, 5:43 PM EDT | Severe Thunderstorm Warning | APX | Cheboygan, Emmet, Presque Isle | 47 min |
| Aug 11, 5:52 PM EDT | Severe Thunderstorm Warning | APX | Cheboygan, Presque Isle | 38 min |
| Aug 11, 6:00 PM EDT | Severe Thunderstorm Warning | APX | Benzie, Leelanau | 30 min |
| Aug 11, 6:09 PM EDT | Severe Thunderstorm Warning | APX | Antrim, Crawford, Kalkaska, Otsego | 35 min |
| Aug 11, 6:24 PM EDT | Severe Thunderstorm Warning | APX | Antrim, Benzie, Grand Traverse, Kalkaska, Leelanau | 51 min |
| Aug 11, 6:31 PM EDT | Severe Thunderstorm Warning | APX | Crawford, Montmorency, Oscoda, Otsego | 44 min |
| Aug 11, 6:58 PM EDT | Severe Thunderstorm Warning | APX | Alcona, Alpena, Presque Isle | 47 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Alpena, MI (KAPX), launched 12:00Z, 8.8 hours before the alert went out and 171 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
- 2 J/kg
- Mixed-layer CIN
- -340 J/kg
- Mixed-layer LCL
- 1366 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 158 m²/s²
- 0-3 km storm-relative helicity
- 172 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
510 WWUS20 KWNS 112037 SEL8 SPC WW 112037 MIZ000-LHZ000-LMZ000-120300- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 428 NWS Storm Prediction Center Norman OK 440 PM EDT Wed Aug 11 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Lower Michigan Lake Huron Lake Michigan * Effective this Wednesday afternoon and evening from 440 PM until 1100 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible A tornado or two possible SUMMARY...Severe storms will spread into northern Lower Michigan from Lake Michigan over the next couple of hours. Northern Lower Michigan was not affected by earlier storms to the south, and the storm environment remains favorable for a mix of supercells and clusters/line segments capable of producing damaging winds to 70 mph, isolated large hail to 1.5 inch diameter, and an isolated tornado or two through late evening. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 15 miles east northeast of Pellston MI to 40 miles east of Manistee MI. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU8). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 424...WW 425...WW 426...WW 427... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 28035. ...Thompson
SPC 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, 7:45 PM EDT | Mesoscale Discussion | SPC | Allegan, Barry, Calhoun, Cass, Clinton, Eaton and 15 more | 90 min |
Nearby
Severe Thunderstorm Watches in Michigan, 2021Every severe thunderstorm watch 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.