Alert archive / Illinois / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 445

August 10, 201723 counties in Illinois; 19 counties in Wisconsin

The Storm Prediction Center issued this severe thunderstorm watch at Aug 10, 2017, 2:47 PM CDT for 23 counties in Illinois; 19 counties in Wisconsin. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Aug 10, 2017, 2:47 PM CDT (19:47 UTC)
Expired
Aug 10, 2017, 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 42 counties

Boone County, IL, Bureau County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Henry County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Putnam County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, Calumet County, WI, Columbia County, WI, Dane County, WI, Dodge County, WI, Fond du Lac County, WI, Green County, WI, Green Lake County, WI, Jefferson County, WI, Kenosha County, WI, Manitowoc County, WI, Milwaukee County, WI, Ozaukee County, WI, Racine County, WI, Rock County, WI, Sheboygan County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI, Winnebago County, WI

The radar

The Milwaukee radar (KMKX), 32 km from the middle of the area, began a volume at 19:49 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
10%
One or more EF2 to EF5 tornadoes
2%
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
20%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Aug 10, 2:57 PM CDTSevere Thunderstorm WarningDVNJo Daviess, Stephenson48 min
Aug 10, 3:06 PM CDTSevere Thunderstorm WarningMKXGreen, Rock39 min
Aug 10, 3:26 PM CDTSevere Thunderstorm WarningMKXOzaukee, Washington49 min
Aug 10, 3:30 PM CDTSevere Thunderstorm WarningMKXRock, Walworth30 min
Aug 10, 4:06 PM CDTSevere Thunderstorm WarningLOTBoone, McHenry24 min
Aug 10, 4:10 PM CDTSevere Thunderstorm WarningMKXDodge, Fond du Lac, Sheboygan, Washington35 min
Aug 10, 4:10 PM CDTSevere Thunderstorm WarningMKXColumbia, Dodge, Fond du Lac, Green Lake35 min
Aug 10, 4:19 PM CDTSevere Thunderstorm WarningMKXDodge, Fond du Lac26 min
Aug 10, 4:37 PM CDTSevere Thunderstorm WarningMKXSheboygan38 min
Aug 10, 4:46 PM CDTSevere Thunderstorm WarningDVNRock Island, Whiteside44 min
Aug 10, 5:14 PM CDTSevere Thunderstorm WarningDVNHenderson, Mercer, Warren15 min
Aug 10, 5:30 PM CDTSevere Thunderstorm WarningDVNBureau, Henry, Whiteside45 min
Aug 10, 6:20 PM CDTSevere Thunderstorm WarningDVNBureau, Henry, Whiteside55 min
Aug 10, 7:32 PM CDTSevere Thunderstorm WarningDVNBureau, Putnam15 min
Aug 10, 7:36 PM CDTSevere Thunderstorm WarningLOTLaSalle, Livingston39 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, 7.8 hours before the alert went out and 202 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 12:00Z on 2017-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 6 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 12:00Z on 2017-08-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 109 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
6 J/kg
Mixed-layer CIN
-122 J/kg
Mixed-layer LCL
1550 m above ground
0-6 km bulk shear
30 kt
0-1 km storm-relative helicity
109 m²/s²
0-3 km storm-relative helicity
87 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 10, 2:07 PM CDTMesoscale DiscussionSPCBoone, Bureau, Carroll, DeKalb, Henderson, Henry and 11 more113 min
Aug 10, 5:31 PM CDTMesoscale DiscussionSPCBoone, Bureau, Carroll, Cook, DeKalb, DuPage and 23 more89 min

Nearby

Severe Thunderstorm Watches in Illinois, 2017Severe Thunderstorm Watches in Wisconsin, 2017Every severe thunderstorm 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.