Alert archive / Illinois / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 84
The Storm Prediction Center issued this severe thunderstorm watch at Apr 3, 2011, 8:11 PM CDT for 18 counties in Illinois; 18 counties in Missouri. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 3, 2011, 8:11 PM CDT (01:11 UTC)
- Expired
- Apr 4, 2011, 2:00 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 36 counties
Adams County, IL, Brown County, IL, Calhoun County, IL, Cass County, IL, Fulton County, IL, Greene County, IL, Knox County, IL, Marshall County, IL, Mason County, IL, Menard County, IL, Morgan County, IL, Peoria County, IL, Pike County, IL, Schuyler County, IL, Scott County, IL, Stark County, IL, Tazewell County, IL, Woodford County, IL, Audrain County, MO, Boone County, MO, Callaway County, MO, Cole County, MO, Franklin County, MO, Gasconade County, MO, Knox County, MO, Lewis County, MO, Lincoln County, MO, Marion County, MO, Moniteau County, MO, Monroe County, MO, Montgomery County, MO, Osage County, MO, Pike County, MO, Ralls County, MO, Shelby County, MO, Warren County, MO
The radar
The Lincoln radar (KILX), 152 km from the middle of the area, began a volume at 01:14 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
- 30%
- Ten or more severe hail reports
- 60%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 80%
Warnings issued inside it
8 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 3, 8:34 PM CDT | Severe Thunderstorm Warning | LSX | Knox | 40 min |
| Apr 3, 9:30 PM CDT | Severe Thunderstorm Warning | LSX | Lewis | 30 min |
| Apr 3, 9:33 PM CDT | Severe Thunderstorm Warning | LSX | Lewis | 24 min |
| Apr 3, 11:14 PM CDT | Severe Thunderstorm Warning | LSX | Audrain, Boone, Lewis, Marion, Monroe, Pike and 2 more | 46 min |
| Apr 3, 11:21 PM CDT | Severe Thunderstorm Warning | LSX | Boone, Cole, Moniteau | 39 min |
| Apr 3, 11:54 PM CDT | Severe Thunderstorm Warning | LSX | Audrain, Boone, Callaway, Cole, Montgomery, Osage | 35 min |
| Apr 4, 12:25 AM CDT | Severe Thunderstorm Warning | LSX | Boone, Cole, Moniteau | 30 min |
| Apr 4, 12:41 AM CDT | Severe Thunderstorm Warning | ILX | Cass, Fulton, Logan, Mason, Menard, Peoria and 2 more | 49 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
Davenport, (KDVN), launched 00:00Z, 1.2 hours before the alert went out and 165 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
- 1790 J/kg
- Mixed-layer CIN
- -85 J/kg
- Mixed-layer LCL
- 1684 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 119 m²/s²
- 0-3 km storm-relative helicity
- 168 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 5.9
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 3, 7:44 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Fulton, Hancock, Henderson and 16 more | 61 min |
| Apr 3, 8:54 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Cook, DeKalb, DuPage, Grundy, Kane and 9 more | 5 hr |
| Apr 3, 10:23 PM CDT | Mesoscale Discussion | SPC | Boone, Carroll, Cook, DeKalb, DuPage, Jo Daviess and 10 more | 67 min |
| Apr 3, 10:50 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Cass, Fulton, Hancock, McDonough and 4 more | 85 min |
| Apr 4, 1:29 AM CDT | Mesoscale Discussion | SPC | Adams, Bond, Brown, Calhoun, Cass, Christian and 31 more | 91 min |
| Apr 4, 1:53 AM CDT | Mesoscale Discussion | SPC | Cook, DuPage, Grundy, Kane, Kendall, Lake and 2 more | 97 min |
| Apr 4, 4:20 AM CDT | Mesoscale Discussion | SPC | Clark, Clay, Crawford, Effingham, Jasper, Lawrence and 2 more | 25 min |
| Apr 4, 6:53 AM CDT | Mesoscale Discussion | SPC | Hardin, Lawrence, Wabash | 2 hr |
| Apr 4, 7:22 AM CDT | Tornado Watch | SPC | Alexander, Edwards, Franklin, Gallatin, Hamilton, Hardin and 13 more | 7 hr |
| Apr 3, 7:26 PM CDT | Mesoscale Discussion | SPC | Adair, Andrew, Buchanan, Caldwell, Carroll, Chariton and 16 more | 64 min |
| Apr 3, 8:15 PM CDT | Mesoscale Discussion | SPC | Adair, Andrew, Barton, Bates, Buchanan, Caldwell and 22 more | 60 min |
| Apr 3, 8:33 PM CDT | Severe Thunderstorm Watch | SPC | Barton, Benton, Camden, Cedar, Dade, Hickory and 5 more | 5 hr |
| Apr 3, 9:51 PM CDT | Mesoscale Discussion | SPC | Barry, McDonald, Newton | 84 min |
| Apr 3, 11:02 PM CDT | Mesoscale Discussion | SPC | Barton, Camden, Cedar, Dade, Dallas, Greene and 10 more | 88 min |
| Apr 4, 5:48 AM CDT | Mesoscale Discussion | SPC | Oregon, Ripley | 117 min |
Nearby
Severe Thunderstorm Watches in Illinois, 2011Severe Thunderstorm Watches in Missouri, 2011Every severe thunderstorm watch in 2011
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.