Alert archive / Illinois / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 187

April 25, 201238 counties in Illinois; Lee County, Van Buren County, Iowa; 10 counties in Missouri

The Storm Prediction Center issued this severe thunderstorm watch at Apr 25, 2012, 7:47 PM CDT for 38 counties in Illinois; Lee County, Van Buren County, Iowa; 10 counties in Missouri. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Apr 25, 2012, 7:47 PM CDT (00:47 UTC)
Expired
Apr 26, 2012, 1:33 AM CDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt
All 50 counties

Lee County, IA, Van Buren County, IA, Adams County, IL, Bond County, IL, Brown County, IL, Calhoun County, IL, Cass County, IL, Christian County, IL, Clay County, IL, Clinton County, IL, Crawford County, IL, DeWitt County, IL, Effingham County, IL, Fayette County, IL, Fulton County, IL, Greene County, IL, Hancock County, IL, Jasper County, IL, Jersey County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Mason County, IL, McDonough County, IL, Menard County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Piatt County, IL, Pike County, IL, Richland County, IL, Saint Clair County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Shelby County, IL, Washington County, IL, Clark County, MO, Knox County, MO, Lewis County, MO, Lincoln County, MO, Marion County, MO, Monroe County, MO, Pike County, MO, Ralls County, MO, Scotland County, MO, Shelby County, MO

The radar

The Lincoln radar (KILX), 123 km from the middle of the area, began a volume at 00:49 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
20%
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
20%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

14 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 25, 7:51 PM CDTSevere Thunderstorm WarningDVNHancock54 min
Apr 25, 8:15 PM CDTSevere Thunderstorm WarningDVNHancock39 min
Apr 25, 8:21 PM CDTSevere Thunderstorm WarningLSXAdams54 min
Apr 25, 9:13 PM CDTSevere Thunderstorm WarningLSXAdams, Brown, Pike62 min
Apr 25, 9:50 PM CDTSevere Thunderstorm WarningLSXPike40 min
Apr 25, 9:55 PM CDTSevere Thunderstorm WarningILXMorgan, Scott65 min
Apr 25, 10:21 PM CDTSevere Thunderstorm WarningLSXGreene, Pike39 min
Apr 25, 10:53 PM CDTSevere Thunderstorm WarningLSXGreene, Jersey, Macoupin67 min
Apr 25, 11:38 PM CDTSevere Thunderstorm WarningLSXFayette37 min
Apr 25, 11:44 PM CDTSevere Thunderstorm WarningLSXBond, Madison, Montgomery46 min
Apr 25, 11:55 PM CDTSevere Thunderstorm WarningILXClay, Effingham, Jasper, Richland65 min
Apr 25, 11:55 PM CDTSevere Thunderstorm WarningLSXMadison50 min
Apr 26, 12:18 AM CDTSevere Thunderstorm WarningLSXClinton, Madison42 min
Apr 26, 12:45 AM CDTSevere Thunderstorm WarningLSXWashington45 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, 0.8 hours before the alert went out and 175 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.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2012-04-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1209 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2012-04-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 2 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1209 J/kg
Mixed-layer CIN
-93 J/kg
Mixed-layer LCL
1553 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
2 m²/s²
0-3 km storm-relative helicity
123 m²/s²
Significant tornado parameter
0.2
Supercell composite
1.8

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 25, 10:11 PM CDTMesoscale DiscussionSPCAdams, Bond, Brown, Calhoun, Cass, Christian and 40 more2 hr
Apr 26, 12:40 AM CDTSevere Thunderstorm WatchSPCEdwards, Franklin, Gallatin, Hamilton, Hardin, Jackson and 10 more6 hr
Apr 26, 2:23 AM CDTMesoscale DiscussionSPCEdwards, Franklin, Gallatin, Hamilton, Hardin, Jefferson and 8 more97 min

Nearby

Severe Thunderstorm Watches in Illinois, 2012Severe Thunderstorm Watches in Missouri, 2012Severe Thunderstorm Watches in Iowa, 2012Every severe thunderstorm watch in 2012

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.