Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 1250

August 6, 201811 counties in Illinois; 8 counties in Indiana

The Storm Prediction Center issued this mesoscale discussion at Aug 6, 2018, 5:21 PM CDT for 11 counties in Illinois; 8 counties in Indiana. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: Aug 6, 2018, 5:21 PM CDT (22:21 UTC)
Expired: Aug 6, 2018, 7:15 PM CDT
In force: 114 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Champaign County, IL, DeWitt County, IL, Ford County, IL, Iroquois County, IL, Kankakee County, IL, Livingston County, IL, Logan County, IL, McLean County, IL, Piatt County, IL, Tazewell County, IL, Vermilion County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, LaPorte County, IN, Newton County, IN, Porter County, IN, Pulaski County, IN, Starke County, IN

The radar

The Chicago radar (KLOT), 84 km from the middle of the area, began a volume at 22:22 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.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 10.4 hours before the alert went out and 90 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 887 J/kg
Mixed-layer CIN: -148 J/kg
Mixed-layer LCL: 1423 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 136 m²/s²
0-3 km storm-relative helicity: 92 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 5, 7:58 PM CDT	Severe Thunderstorm Watch	SPC	Boone, Cook, DeKalb, DuPage, Kane, Lake and 3 more	83 min
Aug 6, 3:16 PM CDT	Mesoscale Discussion	SPC	Alexander, Clay, Edwards, Franklin, Gallatin, Hamilton and 19 more	2 hr
Aug 6, 12:26 PM CDT	Mesoscale Discussion	SPC	DeKalb, LaGrange, Noble, Steuben	3 hr
Aug 6, 12:47 PM CDT	Severe Thunderstorm Watch	SPC	DeKalb, LaGrange, Noble, Steuben	5 hr

Nearby

Mesoscale Discussions in Illinois, 2018 Mesoscale Discussions in Indiana, 2018 Every mesoscale discussion in 2018

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.