Alert archive / Indiana / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 430
The Storm Prediction Center issued this severe thunderstorm watch at Aug 11, 2021, 8:22 PM CDT for 17 counties in Illinois; 19 counties in Indiana; 15 counties in Michigan. It was in force for 8 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 8:22 PM CDT (01:22 UTC)
- Expired
- Aug 12, 2021, 4:00 AM CDT
- In force
- 8 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 55 kt
All 51 counties
Bureau County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, McHenry County, IL, Putnam County, IL, Will County, IL, Benton County, IN, Cass County, IN, Elkhart County, IN, Fulton County, IN, Jasper County, IN, Kosciusko County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Newton County, IN, Noble County, IN, Porter County, IN, Pulaski County, IN, Saint Joseph County, IN, Starke County, IN, Steuben County, IN, White County, IN, Whitley County, IN, Allegan County, MI, Barry County, MI, Berrien County, MI, Branch County, MI, Calhoun County, MI, Cass County, MI, Clinton County, MI, Eaton County, MI, Hillsdale County, MI, Ingham County, MI, Ionia County, MI, Jackson County, MI, Kalamazoo County, MI, Saint Joseph County, MI, Van Buren County, MI
The radar
The Chicago radar (KLOT), 41 km from the middle of the area, began a volume at 01:25 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
- 30%
- One or more gusts of 65 knots or more
- 5%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 8:30 PM CDT | Severe Thunderstorm Warning | GRR | Barry, Clinton, Eaton, Ionia | 45 min |
| Aug 11, 8:57 PM CDT | Severe Thunderstorm Warning | LOT | DuPage, Kane | 48 min |
| Aug 11, 9:43 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage | 26 min |
| Aug 12, 2:13 AM CDT | Severe Thunderstorm Warning | LOT | Ford, Iroquois, Kankakee, Livingston | 47 min |
| Aug 12, 2:30 AM CDT | Severe Thunderstorm Warning | LOT | Kankakee, Will | 29 min |
| Aug 12, 2:55 AM CDT | Severe Thunderstorm Warning | LOT | Cook | 50 min |
| Aug 12, 3:02 AM CDT | Severe Thunderstorm Warning | LOT | LaSalle | 43 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
Lincoln, IL (KILX), launched 00:00Z, 1.4 hours before the alert went out and 208 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
- 3800 J/kg
- Mixed-layer CIN
- -58 J/kg
- Mixed-layer LCL
- 1058 m above ground
- 0-6 km bulk shear
- 19 kt
- 0-1 km storm-relative helicity
- 255 m²/s²
- 0-3 km storm-relative helicity
- 406 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 20.7
The text
As transmitted.
437 WWUS20 KWNS 120121 SEL0 SPC WW 120121 ILZ000-INZ000-MIZ000-LMZ000-120700- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 430 NWS Storm Prediction Center Norman OK 820 PM CDT Wed Aug 11 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of parts of northern Illinois northern Indiana parts of southern Lower Michigan Lake Michigan * Effective this Wednesday night and Thursday morning from 820 PM until 200 AM CDT. * Primary threats include... Isolated damaging wind gusts to 65 mph possible Isolated large hail events to 1.5 inches in diameter possible A tornado or two possible SUMMARY...Thunderstorms are forecast to increase in coverage over the next couple of hours across the watch area, with the stronger storms capable of producing wind gusts to severe levels, as well as hail in excess of 1" in diameter through the evening hours. The severe thunderstorm watch area is approximately along and 55 statute miles north and south of a line from 50 miles southwest of Rockford IL to 25 miles southeast of Kalamazoo MI. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). 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. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 27040. ...Goss
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 7:35 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 20 more | 85 min |
| Aug 11, 11:06 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 15 more | 84 min |
| Aug 12, 3:16 AM CDT | Mesoscale Discussion | SPC | Bureau, Ford, Fulton, Grundy, Iroquois, Kankakee and 16 more | 119 min |
| Aug 12, 2:22 PM CDT | Mesoscale Discussion | SPC | Bond, Cass, Champaign, Christian, Clark, Clay and 26 more | 83 min |
| Aug 12, 5:19 PM CDT | Severe Thunderstorm Watch | SPC | Calhoun, Clinton, Greene, Jersey, Macoupin, Madison and 7 more | 5 hr |
| Aug 12, 6:06 PM CDT | Mesoscale Discussion | SPC | Calhoun, Jersey, Madison, Monroe, Saint Clair | 84 min |
| Aug 11, 9:17 PM CDT | Mesoscale Discussion | SPC | Genesee, Lapeer, Livingston, Macomb, Oakland, Saint Clair and 3 more | 88 min |
| Aug 12, 5:38 AM CDT | Mesoscale Discussion | SPC | Hillsdale, Jackson, Lenawee, Monroe, Oakland, Washtenaw and 1 more | 97 min |
Nearby
Severe Thunderstorm Watches in Indiana, 2021Severe Thunderstorm Watches in Illinois, 2021Severe 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.