Alert archive / Illinois / Tornado Watches in 2015
Tornado Watch 41
The Storm Prediction Center issued this tornado watch at Apr 9, 2015, 1:48 PM CDT for 42 counties in Illinois; 5 counties in Indiana; 8 counties in Wisconsin. It was in force for 9 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 9, 2015, 1:48 PM CDT (18:48 UTC)
- Expired
- Apr 9, 2015, 11:00 PM CDT
- In force
- 9 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2.5 in
- Strongest gust expected
- 70 kt
All 55 counties
Boone County, IL, Bureau County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Cook County, IL, DeKalb County, IL, DeWitt County, IL, DuPage County, IL, Ford County, IL, Fulton County, IL, Grundy 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, Ogle County, IL, Peoria County, IL, Piatt County, IL, Putnam County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Stark County, IL, Tazewell County, IL, Vermilion County, IL, Will County, IL, Winnebago County, IL, Woodford County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN, Green County, WI, Jefferson County, WI, Kenosha County, WI, Milwaukee County, WI, Racine County, WI, Rock County, WI, Walworth County, WI, Waukesha County, WI
The radar
The Chicago radar (KLOT), 66 km from the middle of the area, began a volume at 18:48 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
- 60%
- One or more EF2 to EF5 tornadoes
- 40%
- Ten or more severe wind reports
- 60%
- One or more gusts of 65 knots or more
- 40%
- Ten or more severe hail reports
- 50%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 95%
Warnings issued inside it
48 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 9, 4:59 PM CDT | Severe Thunderstorm Warning | MKX | Rock, Walworth | 31 min |
| Apr 9, 5:12 PM CDT | Severe Thunderstorm Warning | MKX | Rock | 21 min |
| Apr 9, 5:15 PM CDT | Severe Thunderstorm Warning | ILX | Fulton, Peoria, Tazewell | 45 min |
| Apr 9, 5:27 PM CDT | Severe Thunderstorm Warning | LOT | Boone, Winnebago | 18 min |
| Apr 9, 5:36 PM CDT | Severe Thunderstorm Warning | MKX | Rock, Walworth | 24 min |
| Apr 9, 6:01 PM CDT | Severe Thunderstorm Warning | ILX | Morgan, Scott | 44 min |
| Apr 9, 6:09 PM CDT | Tornado Warning | LOT | Boone, DeKalb, Ogle, Winnebago | 36 min |
| Apr 9, 6:11 PM CDT | Severe Thunderstorm Warning | LOT | Lee, Ogle | 34 min |
| Apr 9, 6:27 PM CDT | Severe Thunderstorm Warning | LOT | Ogle | 33 min |
| Apr 9, 6:35 PM CDT | Tornado Warning | LOT | Lee, Ogle | 25 min |
| Apr 9, 6:37 PM CDT | Tornado Warning | LOT | Boone, Winnebago | 23 min |
| Apr 9, 6:42 PM CDT | Severe Thunderstorm Warning | ILX | Morgan, Sangamon | 48 min |
| Apr 9, 6:49 PM CDT | Severe Thunderstorm Warning | LOT | Ogle, Winnebago | 26 min |
| Apr 9, 6:56 PM CDT | Severe Thunderstorm Warning | ILX | Knox, Marshall, Peoria, Stark, Woodford | 49 min |
| Apr 9, 6:56 PM CDT | Tornado Warning | LOT | Boone, McHenry | 34 min |
| Apr 9, 6:58 PM CDT | Tornado Warning | LOT | Boone, DeKalb, Ogle, Winnebago | 47 min |
| Apr 9, 7:05 PM CDT | Tornado Warning | LOT | Boone, Ogle, Winnebago | 40 min |
| Apr 9, 7:09 PM CDT | Severe Thunderstorm Warning | MKX | Kenosha, Racine, Walworth | 36 min |
| Apr 9, 7:16 PM CDT | Tornado Warning | LOT | Boone, DeKalb, McHenry | 29 min |
| Apr 9, 7:16 PM CDT | Severe Thunderstorm Warning | MKX | Rock, Walworth | 29 min |
| Apr 9, 7:19 PM CDT | Severe Thunderstorm Warning | LOT | Lee, Ogle | 26 min |
| Apr 9, 7:19 PM CDT | Tornado Warning | LOT | McHenry | 26 min |
| Apr 9, 7:23 PM CDT | Severe Thunderstorm Warning | DVN | Bureau, Putnam | 24 min |
| Apr 9, 7:24 PM CDT | Tornado Warning | ILX | Christian, Sangamon | 21 min |
| Apr 9, 7:26 PM CDT | Severe Thunderstorm Warning | MKX | Kenosha, Racine, Walworth | 34 min |
| Apr 9, 7:32 PM CDT | Tornado Warning | ILX | Marshall, Peoria, Woodford | 28 min |
| Apr 9, 7:36 PM CDT | Severe Thunderstorm Warning | LOT | Ogle, Winnebago | 24 min |
| Apr 9, 7:36 PM CDT | Severe Thunderstorm Warning | MKX | Rock, Walworth | 24 min |
| Apr 9, 7:41 PM CDT | Tornado Warning | ILX | Christian, Macon | 34 min |
| Apr 9, 7:41 PM CDT | Tornado Warning | LOT | McHenry | 49 min |
| Apr 9, 7:43 PM CDT | Severe Thunderstorm Warning | MKX | Kenosha, Milwaukee, Racine, Walworth, Waukesha | 32 min |
| Apr 9, 7:48 PM CDT | Severe Thunderstorm Warning | MKX | Kenosha, Racine, Walworth | 27 min |
| Apr 9, 7:51 PM CDT | Tornado Warning | LOT | LaSalle | 39 min |
| Apr 9, 7:53 PM CDT | Severe Thunderstorm Warning | LOT | Boone, DeKalb, Kane, McHenry, Ogle, Winnebago | 37 min |
| Apr 9, 7:57 PM CDT | Severe Thunderstorm Warning | ILX | Marshall, Woodford | 33 min |
| Apr 9, 7:58 PM CDT | Tornado Warning | MKX | Kenosha, Racine, Walworth | 32 min |
| Apr 9, 8:05 PM CDT | Severe Thunderstorm Warning | LOT | McHenry | 55 min |
| Apr 9, 8:13 PM CDT | Tornado Warning | ILX | Christian, Macon, Moultrie, Shelby | 32 min |
| Apr 9, 8:14 PM CDT | Severe Thunderstorm Warning | MKX | Kenosha, Milwaukee, Racine | 31 min |
| Apr 9, 8:21 PM CDT | Severe Thunderstorm Warning | LOT | LaSalle | 24 min |
| Apr 9, 8:21 PM CDT | Severe Thunderstorm Warning | LOT | Lake | 24 min |
| Apr 9, 8:40 PM CDT | Severe Thunderstorm Warning | LOT | Grundy, Kendall, LaSalle, Will | 35 min |
| Apr 9, 8:58 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage, Kendall, Will | 32 min |
| Apr 9, 9:01 PM CDT | Severe Thunderstorm Warning | ILX | Piatt | 18 min |
| Apr 9, 9:08 PM CDT | Severe Thunderstorm Warning | LOT | Cook, Will | 37 min |
| Apr 9, 9:16 PM CDT | Severe Thunderstorm Warning | ILX | Champaign | 28 min |
| Apr 9, 9:25 PM CDT | Severe Thunderstorm Warning | LOT | Cook, DuPage, Will | 35 min |
| Apr 9, 9:40 PM CDT | Severe Thunderstorm Warning | LOT | Ford, Iroquois | 35 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, 6.8 hours before the alert went out and 136 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
- 101 J/kg
- Mixed-layer CIN
- -154 J/kg
- Mixed-layer LCL
- 614 m above ground
- 0-6 km bulk shear
- 55 kt
- 0-1 km storm-relative helicity
- 323 m²/s²
- 0-3 km storm-relative helicity
- 253 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.4
The text
As transmitted, in the capitals the NWS used until 2016.
145
WWUS20 KWNS 091849
SEL1
SPC WW 091849
ILZ000-INZ000-WIZ000-LMZ000-100400-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 41
NWS STORM PREDICTION CENTER NORMAN OK
150 PM CDT THU APR 9 2015
THE NWS STORM PREDICTION CENTER HAS ISSUED A
* TORNADO WATCH FOR PORTIONS OF
NORTHERN AND CENTRAL ILLINOIS
FAR NORTHWEST INDIANA
FAR SOUTHERN WISCONSIN
LAKE MICHIGAN
* EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 150 PM UNTIL
1100 PM CDT.
* PRIMARY THREATS INCLUDE...
A FEW TORNADOES LIKELY WITH A COUPLE INTENSE TORNADOES POSSIBLE
SCATTERED DAMAGING WINDS LIKELY WITH ISOLATED SIGNIFICANT GUSTS
TO 80 MPH POSSIBLE
SCATTERED LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 2.5
INCHES IN DIAMETER POSSIBLE
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 15 MILES NORTHWEST OF
MILWAUKEE WISCONSIN TO 25 MILES SOUTHWEST OF DECATUR ILLINOIS.
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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 39...WW 40...
DISCUSSION...TWO ROUNDS OF SEVERE CONVECTION ARE EXPECTED WITH
INITIAL STORMS IN CENTRAL ILLINOIS DEVELOPING E/NE AND ADDITIONAL
STORMS ALONG A FRONTAL ZONE. BOTH AREAS WILL HAVE STRONG DEEP-LAYER
SHEAR SUPPORTING RISKS FOR A FEW TORNADOES...LARGE HAIL AND DAMAGING
WINDS.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24040.
...GRAMS/CORFIDISPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 8, 7:04 PM CDT | Mesoscale Discussion | SPC | Franklin, Gallatin, Hardin, Jackson, Johnson, Pope and 3 more | 116 min |
| Apr 9, 12:29 PM CDT | Mesoscale Discussion | SPC | Bureau, Carroll, Henderson, Henry, Jo Daviess, Knox and 8 more | 91 min |
| Apr 9, 12:58 PM CDT | Tornado Watch | SPC | Adams, Brown, Carroll, Hancock, Henderson, Henry and 8 more | 6 hr |
| Apr 9, 3:12 PM CDT | Mesoscale Discussion | SPC | Adams, Boone, Brown, Bureau, Calhoun, Carroll and 51 more | 93 min |
| Apr 9, 3:45 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Clay, Clinton, Cumberland, Effingham and 25 more | 60 min |
| Apr 9, 4:40 PM CDT | Tornado Watch | SPC | Bond, Calhoun, Clinton, Fayette, Greene, Jersey and 8 more | 6 hr |
| Apr 9, 6:04 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cass, DeKalb, DeWitt and 37 more | 86 min |
| Apr 9, 6:48 PM CDT | Tornado Watch | SPC | Alexander, Clark, Clay, Coles, Crawford, Cumberland and 26 more | 6 hr |
| Apr 9, 12:51 PM CDT | Mesoscale Discussion | SPC | Dearborn | 54 min |
| Apr 9, 1:26 PM CDT | Severe Thunderstorm Watch | SPC | Dearborn, Ohio, Ripley, Switzerland | 8 hr |
| Apr 9, 3:01 PM CDT | Mesoscale Discussion | SPC | Dearborn, Ohio, Ripley, Switzerland | 59 min |
| Apr 9, 3:49 PM CDT | Mesoscale Discussion | SPC | Clark, Dearborn, Floyd, Franklin, Jefferson, Jennings and 5 more | 56 min |
| Apr 9, 4:46 PM CDT | Mesoscale Discussion | SPC | Calumet, Columbia, Dane, Dodge, Fond du Lac, Green Lake and 6 more | 89 min |
| Apr 9, 5:15 PM CDT | Severe Thunderstorm Watch | SPC | Columbia, Dane, Dodge, Fond du Lac, Green Lake, Iowa and 6 more | 4 hr |
Nearby
Tornado Watches in Illinois, 2015Tornado Watches in Wisconsin, 2015Tornado Watches in Indiana, 2015Every tornado watch in 2015
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.