Alert archive / Illinois / Tornado Watches in 2021
Tornado Watch 521
The Storm Prediction Center issued this tornado watch at Oct 11, 2021, 3:10 PM CDT for 51 counties in Illinois. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 11, 2021, 3:10 PM CDT (20:10 UTC)
- Expired
- Oct 11, 2021, 9:00 PM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 51 counties
Boone County, IL, Bureau County, IL, Carroll County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Coles County, IL, Cook County, IL, Cumberland County, IL, DeKalb County, IL, DeWitt County, IL, Douglas County, IL, DuPage County, IL, Edgar County, IL, Effingham County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Logan County, IL, Macon County, IL, Marshall County, IL, Mason County, IL, McHenry County, IL, McLean County, IL, Menard County, IL, Morgan County, IL, Moultrie County, IL, Ogle County, IL, Peoria County, IL, Piatt County, IL, Putnam County, IL, Sangamon County, IL, Shelby County, IL, Stark County, IL, Tazewell County, IL, Vermilion County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL
The radar
The Lincoln radar (KILX), 56 km from the middle of the area, began a volume at 20:12 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
- 50%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- 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
- 60%
Warnings issued inside it
15 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 11, 3:12 PM CDT | Tornado Warning | ILX | Morgan, Sangamon | 33 min |
| Oct 11, 3:32 PM CDT | Tornado Warning | ILX | Cass, Menard, Morgan, Sangamon | 30 min |
| Oct 11, 3:50 PM CDT | Tornado Warning | ILX | Fulton, Mason, Tazewell | 25 min |
| Oct 11, 4:21 PM CDT | Tornado Warning | ILX | Logan, Mason | 24 min |
| Oct 11, 4:47 PM CDT | Tornado Warning | ILX | Marshall, Woodford | 28 min |
| Oct 11, 4:56 PM CDT | Severe Thunderstorm Warning | ILX | DeWitt, Logan, Macon, Piatt | 49 min |
| Oct 11, 5:03 PM CDT | Severe Thunderstorm Warning | ILX | DeWitt, Logan, McLean, Macon, Piatt | 42 min |
| Oct 11, 5:12 PM CDT | Tornado Warning | DVN | Putnam | 48 min |
| Oct 11, 5:14 PM CDT | Severe Thunderstorm Warning | ILX | McLean, Woodford | 61 min |
| Oct 11, 5:37 PM CDT | Severe Thunderstorm Warning | LOT | Ford, Grundy, LaSalle, Livingston | 68 min |
| Oct 11, 5:38 PM CDT | Tornado Warning | ILX | Woodford | 20 min |
| Oct 11, 5:42 PM CDT | Severe Thunderstorm Warning | ILX | Champaign, DeWitt, Douglas, McLean, Macon, Piatt | 63 min |
| Oct 11, 5:58 PM CDT | Tornado Warning | DVN | Bureau, Putnam | 47 min |
| Oct 11, 6:44 PM CDT | Severe Thunderstorm Warning | LOT | DeKalb, LaSalle, Lee, Ogle | 61 min |
| Oct 11, 6:49 PM CDT | Tornado Warning | LOT | LaSalle, Lee | 13 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 12:00Z, 8.2 hours before the alert went out and 60 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
- 287 J/kg
- Mixed-layer CIN
- -72 J/kg
- Mixed-layer LCL
- 867 m above ground
- 0-6 km bulk shear
- 52 kt
- 0-1 km storm-relative helicity
- 206 m²/s²
- 0-3 km storm-relative helicity
- 230 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 1.3
The text
As transmitted.
581 WWUS20 KWNS 112007 SEL1 SPC WW 112007 ILZ000-INZ000-LMZ000-120200- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 521 NWS Storm Prediction Center Norman OK 310 PM CDT Mon Oct 11 2021 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central and Northern Illinois Northwest Indiana Lake Michigan * Effective this Monday afternoon and evening from 310 PM until 900 PM CDT. * Primary threats include... A few tornadoes possible Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Scattered thunderstorms will intensify across central and northern Illinois this afternoon ahead of an approaching upper low. The strongest cells may become supercells, capable of isolated tornadoes and damaging wind gusts. The tornado watch area is approximately along and 60 statute miles east and west of a line from 35 miles south southwest of Decatur IL to 45 miles east northeast of Rockford IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and 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. && AVIATION...Tornadoes and 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 24035. ...Hart
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 11, 9:06 AM CDT | Mesoscale Discussion | SPC | Adams, Bond, Brown, Calhoun, Cass, Christian and 30 more | 2 hr |
| Oct 11, 12:37 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Cook, DeKalb, DuPage, Grundy and 18 more | 113 min |
| Oct 11, 3:37 PM CDT | Mesoscale Discussion | SPC | LaSalle, Marshall, Mason, Menard, Peoria, Putnam and 3 more | 83 min |
| Oct 11, 6:09 PM CDT | Mesoscale Discussion | SPC | Boone, Champaign, Coles, Cook, DeKalb, Douglas and 13 more | 96 min |
Nearby
Tornado Watches in Illinois, 2021Every tornado 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.