Alert archive / Michigan / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 473
The Storm Prediction Center issued this severe thunderstorm watch at Aug 29, 2021, 1:46 PM EDT for 48 counties in Michigan. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 29, 2021, 1:46 PM EDT (17:46 UTC)
- Expired
- Aug 29, 2021, 8:00 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 65 kt
All 48 counties
Alcona County, MI, Alpena County, MI, Antrim County, MI, Arenac County, MI, Bay County, MI, Benzie County, MI, Charlevoix County, MI, Cheboygan County, MI, Chippewa County, MI, Clare County, MI, Crawford County, MI, Emmet County, MI, Genesee County, MI, Gladwin County, MI, Grand Traverse County, MI, Gratiot County, MI, Huron County, MI, Iosco County, MI, Isabella County, MI, Kalkaska County, MI, Lake County, MI, Lapeer County, MI, Leelanau County, MI, Livingston County, MI, Mackinac County, MI, Macomb County, MI, Manistee County, MI, Mason County, MI, Mecosta County, MI, Midland County, MI, Missaukee County, MI, Montcalm County, MI, Montmorency County, MI, Muskegon County, MI, Newaygo County, MI, Oakland County, MI, Oceana County, MI, Ogemaw County, MI, Osceola County, MI, Oscoda County, MI, Otsego County, MI, Presque Isle County, MI, Roscommon County, MI, Saginaw County, MI, Saint Clair County, MI, Sanilac County, MI, Tuscola County, MI, Wexford County, MI
The radar
The NCL Michigan radar (KAPX), 87 km from the middle of the area, began a volume at 17:49 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
- 10%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
19 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 1:58 PM EDT | Severe Thunderstorm Warning | APX | Cheboygan, Emmet | 47 min |
| Aug 29, 2:12 PM EDT | Severe Thunderstorm Warning | APX | Kalkaska, Missaukee, Wexford | 48 min |
| Aug 29, 2:17 PM EDT | Severe Thunderstorm Warning | APX | Antrim, Charlevoix, Cheboygan, Emmet, Otsego | 43 min |
| Aug 29, 2:28 PM EDT | Severe Thunderstorm Warning | APX | Antrim, Charlevoix, Kalkaska, Otsego | 32 min |
| Aug 29, 2:33 PM EDT | Flash Flood Warning | GRR | Lake | 8 hr |
| Aug 29, 2:55 PM EDT | Severe Thunderstorm Warning | APX | Cheboygan, Montmorency, Otsego, Presque Isle | 35 min |
| Aug 29, 3:01 PM EDT | Severe Thunderstorm Warning | APX | Crawford, Missaukee, Oscoda, Roscommon | 38 min |
| Aug 29, 3:18 PM EDT | Severe Thunderstorm Warning | GRR | Muskegon | 28 min |
| Aug 29, 3:22 PM EDT | Severe Thunderstorm Warning | APX | Alpena, Montmorency, Presque Isle | 53 min |
| Aug 29, 3:36 PM EDT | Severe Thunderstorm Warning | APX | Ogemaw, Oscoda, Roscommon | 24 min |
| Aug 29, 4:30 PM EDT | Severe Thunderstorm Warning | DTX | Saginaw, Shiawassee | 75 min |
| Aug 29, 4:58 PM EDT | Severe Thunderstorm Warning | DTX | Huron | 62 min |
| Aug 29, 5:11 PM EDT | Severe Thunderstorm Warning | DTX | Bay, Genesee, Tuscola | 79 min |
| Aug 29, 5:25 PM EDT | Severe Thunderstorm Warning | DTX | Livingston | 65 min |
| Aug 29, 5:56 PM EDT | Severe Thunderstorm Warning | DTX | Oakland | 64 min |
| Aug 29, 5:58 PM EDT | Severe Thunderstorm Warning | DTX | Lapeer | 62 min |
| Aug 29, 6:00 PM EDT | Severe Thunderstorm Warning | DTX | Huron | 59 min |
| Aug 29, 6:13 PM EDT | Severe Thunderstorm Warning | DTX | Sanilac | 77 min |
| Aug 29, 6:37 PM EDT | Severe Thunderstorm Warning | DTX | Macomb, Saint Clair | 83 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, 5.8 hours before the alert went out and 97 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
- 221 J/kg
- Mixed-layer CIN
- -108 J/kg
- Mixed-layer LCL
- 1035 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 113 m²/s²
- 0-3 km storm-relative helicity
- 149 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.6
The text
As transmitted.
147
WWUS20 KWNS 291743
SEL3
SPC WW 291743
MIZ000-LHZ000-LMZ000-292300-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 473
NWS Storm Prediction Center Norman OK
1245 PM CDT Sun Aug 29 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northern and central Michigan
Lake Huron
Lake Michigan
* Effective this Sunday afternoon and evening from 1245 PM until
600 PM CDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 75
mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...Multiple multicell clusters should spread east across most
of Lower Michigan this afternoon.
The severe thunderstorm watch area is approximately along and 65
statute miles east and west of a line from 80 miles north northeast
of Alpena MI to 45 miles east of Muskegon MI. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).
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 472...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
25030.
...GramsSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 1:05 PM EDT | Mesoscale Discussion | SPC | Alcona, Alpena, Antrim, Arenac, Bay, Cheboygan and 20 more | 115 min |
| Aug 29, 4:08 PM EDT | Mesoscale Discussion | SPC | Allegan, Barry, Berrien, Branch, Calhoun, Cass and 10 more | 97 min |
| Aug 29, 4:27 PM EDT | Mesoscale Discussion | SPC | Alcona, Alpena, Arenac, Barry, Bay, Clinton and 16 more | 93 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.