Alert archive / Illinois / Tornado Watches in 2017
Tornado Watch 234
The Storm Prediction Center issued this tornado watch at May 17, 2017, 3:44 PM CDT for 24 counties in Illinois; 21 counties in Iowa; Clark County, Scotland County, Missouri. It was in force for 9 hr.
The area
The outline as issued.
The facts
- Issued
- May 17, 2017, 3:44 PM CDT (20:44 UTC)
- Expired
- May 18, 2017, 1:00 AM CDT
- In force
- 9 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 47 counties
Benton County, IA, Buchanan County, IA, Cedar County, IA, Clinton County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Linn County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Washington County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Knox County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Marshall County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Stephenson County, IL, Warren County, IL, Whiteside County, IL, Winnebago County, IL, Clark County, MO, Scotland County, MO
The radar
The Quad Cities radar (KDVN), 38 km from the middle of the area, began a volume at 20:46 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
- 30%
- One or more EF2 to EF5 tornadoes
- 10%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
43 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 17, 3:45 PM CDT | Severe Thunderstorm Warning | DVN | Des Moines, Henry, Lee, Van Buren | 30 min |
| May 17, 3:49 PM CDT | Tornado Warning | DVN | Henry, Jefferson, Van Buren, Washington | 41 min |
| May 17, 3:55 PM CDT | Tornado Warning | DVN | Des Moines, Henry, Lee, Louisa, Van Buren | 50 min |
| May 17, 4:23 PM CDT | Severe Thunderstorm Warning | DVN | Iowa, Johnson, Washington | 44 min |
| May 17, 4:40 PM CDT | Tornado Warning | DVN | Mercer, Rock Island | 50 min |
| May 17, 5:03 PM CDT | Severe Thunderstorm Warning | DVN | Benton, Iowa, Keokuk | 57 min |
| May 17, 5:24 PM CDT | Severe Thunderstorm Warning | DVN | Rock Island | 30 min |
| May 17, 5:39 PM CDT | Severe Thunderstorm Warning | DVN | Henry, Jefferson, Keokuk, Van Buren, Washington | 66 min |
| May 17, 5:50 PM CDT | Severe Thunderstorm Warning | DVN | Benton, Buchanan, Delaware, Iowa, Johnson, Linn and 1 more | 55 min |
| May 17, 5:53 PM CDT | Severe Thunderstorm Warning | LOT | Ogle, Winnebago | 51 min |
| May 17, 5:54 PM CDT | Severe Thunderstorm Warning | DVN | Jefferson, Van Buren | 51 min |
| May 17, 5:56 PM CDT | Severe Thunderstorm Warning | DVN | Stephenson | 34 min |
| May 17, 6:01 PM CDT | Tornado Warning | DVN | Henry, Jefferson, Lee, Van Buren | 59 min |
| May 17, 6:19 PM CDT | Tornado Warning | DVN | Johnson, Louisa, Washington | 41 min |
| May 17, 6:28 PM CDT | Flash Flood Warning | DVN | Johnson, Linn | 3 hr |
| May 17, 6:31 PM CDT | Severe Thunderstorm Warning | DVN | Buchanan, Cedar, Clinton, Delaware, Dubuque, Jackson and 5 more | 59 min |
| May 17, 6:32 PM CDT | Tornado Warning | DVN | Delaware, Dubuque, Jones, Linn | 43 min |
| May 17, 6:38 PM CDT | Severe Thunderstorm Warning | DVN | Mercer, Rock Island | 52 min |
| May 17, 6:48 PM CDT | Tornado Warning | DVN | Cedar, Johnson, Muscatine | 42 min |
| May 17, 7:00 PM CDT | Tornado Warning | DVN | Henderson, Mercer, Warren | 45 min |
| May 17, 7:14 PM CDT | Severe Thunderstorm Warning | DVN | Carroll, Jo Daviess, Mercer, Rock Island | 61 min |
| May 17, 7:30 PM CDT | Severe Thunderstorm Warning | DVN | Mercer, Rock Island | 45 min |
| May 17, 7:37 PM CDT | Severe Thunderstorm Warning | DVN | Henry, Mercer, Rock Island, Warren | 38 min |
| May 17, 7:44 PM CDT | Tornado Warning | DVN | Clinton, Scott | 46 min |
| May 17, 8:05 PM CDT | Severe Thunderstorm Warning | DVN | Carroll, Jo Daviess, Stephenson, Whiteside | 55 min |
| May 17, 8:05 PM CDT | Tornado Warning | DVN | Henry, Mercer, Rock Island | 40 min |
| May 17, 8:08 PM CDT | Severe Thunderstorm Warning | DVN | Henry, Mercer, Rock Island, Whiteside | 67 min |
| May 17, 8:46 PM CDT | Tornado Warning | DVN | Bureau, Henry, Whiteside | 23 min |
| May 17, 8:58 PM CDT | Severe Thunderstorm Warning | LOT | Lee, Ogle | 62 min |
| May 17, 9:00 PM CDT | Severe Thunderstorm Warning | DVN | Carroll, Jo Daviess, Rock Island, Stephenson, Whiteside | 60 min |
| May 17, 9:08 PM CDT | Severe Thunderstorm Warning | ILX | Knox | 37 min |
| May 17, 9:37 PM CDT | Severe Thunderstorm Warning | LOT | Ogle, Winnebago | 23 min |
| May 17, 9:38 PM CDT | Severe Thunderstorm Warning | DVN | Bureau, Henry | 52 min |
| May 17, 9:52 PM CDT | Severe Thunderstorm Warning | ILX | Marshall, Stark | 38 min |
| May 17, 9:54 PM CDT | Tornado Warning | LOT | Lee, Ogle | 21 min |
| May 17, 9:59 PM CDT | Severe Thunderstorm Warning | LOT | Boone, DeKalb, LaSalle, Lee, McHenry, Ogle and 1 more | 61 min |
| May 17, 10:04 PM CDT | Tornado Warning | LOT | Boone, Winnebago | 26 min |
| May 17, 10:22 PM CDT | Tornado Warning | LOT | Boone, McHenry | 23 min |
| May 17, 10:43 PM CDT | Severe Thunderstorm Warning | LOT | DeKalb, Kane, Kendall, LaSalle, McHenry | 47 min |
| May 17, 10:53 PM CDT | Severe Thunderstorm Warning | ILX | Marshall, Peoria, Woodford | 32 min |
| May 17, 11:11 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage, Lake | 49 min |
| May 17, 11:29 PM CDT | Severe Thunderstorm Warning | LOT | Kane, Kendall | 31 min |
| May 17, 11:50 PM CDT | Severe Thunderstorm Warning | LOT | DuPage, Grundy, Kane, Kendall, Will | 40 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 12:00Z, 8.7 hours before the alert went out and 44 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
- 103 J/kg
- Mixed-layer CIN
- -348 J/kg
- Mixed-layer LCL
- 1223 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 84 m²/s²
- 0-3 km storm-relative helicity
- 79 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
595 WWUS20 KWNS 172039 SEL4 SPC WW 172039 IAZ000-ILZ000-MOZ000-180400- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 234 NWS Storm Prediction Center Norman OK 340 PM CDT Wed May 17 2017 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of eastern Iowa northwestern Illinois far northeast Missouri * Effective this Wednesday afternoon and evening from 340 PM until 1100 PM CDT. * Primary threats include... A couple tornadoes possible Isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Strong/severe storms continue to develop/spread across eastern Iowa, and are expected to move into parts of northern Illinois over the next several hours. Along with risk for large hail and locally damaging winds, a couple of tornadoes will also be possible. The tornado watch area is approximately along and 65 statute miles north and south of a line from 10 miles north northwest of Ottumwa IA to 25 miles southeast of Rockford IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 231...WW 232...WW 233... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 22040. ...Goss
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 17, 3:24 PM CDT | Mesoscale Discussion | SPC | Carroll, Hancock, Henderson, Henry, Jo Daviess, Knox and 7 more | 66 min |
| May 16, 7:31 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Benton, Black Hawk, Boone and 59 more | 59 min |
| May 16, 8:46 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Black Hawk, Boone, Bremer, Butler, Cerro Gordo and 29 more | 5 hr |
| May 16, 9:43 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Calhoun, Carroll, Cass and 16 more | 62 min |
| May 16, 11:48 PM CDT | Mesoscale Discussion | SPC | Adair, Allamakee, Black Hawk, Boone, Bremer, Butler and 28 more | 117 min |
| May 17, 11:39 AM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Audubon, Boone, Carroll and 28 more | 66 min |
| May 17, 12:08 PM CDT | Tornado Watch | SPC | Adair, Adams, Appanoose, Audubon, Black Hawk, Boone and 64 more | 7 hr |
| May 17, 12:23 PM CDT | Mesoscale Discussion | SPC | Allamakee, Clayton | 97 min |
| May 17, 2:25 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Boone, Calhoun, Carroll and 32 more | 65 min |
| May 17, 2:38 PM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 15 more | 97 min |
| May 17, 3:13 PM CDT | Tornado Watch | SPC | Allamakee, Chickasaw, Clayton, Fayette, Floyd, Howard and 2 more | 9 hr |
| May 17, 6:05 PM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Bremer, Buchanan, Cedar and 18 more | 55 min |
| May 16, 9:14 PM CDT | Mesoscale Discussion | SPC | Buffalo, Chippewa, Clark, Dunn, Eau Claire, Florence and 18 more | 61 min |
| May 16, 9:47 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Buffalo, Clark, Jackson, Juneau, La Crosse and 14 more | 5 hr |
| May 17, 6:31 PM CDT | Mesoscale Discussion | SPC | Adams, Chippewa, Clark, Columbia, Dodge, Eau Claire and 17 more | 89 min |
Nearby
Tornado Watches in Illinois, 2017Tornado Watches in Iowa, 2017Tornado Watches in Missouri, 2017Every tornado watch in 2017
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.