Alert archive / Illinois / Mesoscale Discussions in 2015

Mesoscale Discussion 1709

August 18, 201522 counties in Illinois; 8 counties in Iowa; 13 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2015, 3:53 PM CDT for 22 counties in Illinois; 8 counties in Iowa; 13 counties in Wisconsin. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 18, 2015, 3:53 PM CDT (20:53 UTC)
Expired: Aug 18, 2015, 6:00 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 43 counties

Cedar County, IA, Clinton County, IA, Des Moines County, IA, Dubuque County, IA, Jackson County, IA, Jones County, IA, Muscatine County, IA, Scott County, IA, Boone County, IL, Bureau County, IL, Carroll County, IL, DeKalb County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Knox County, IL, LaSalle County, IL, Lee County, IL, Marshall County, IL, Mercer County, IL, Ogle County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Stephenson County, IL, Warren County, IL, Whiteside County, IL, Winnebago County, IL, Woodford County, IL, Columbia County, WI, Crawford County, WI, Dane County, WI, Dodge County, WI, Grant County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Lafayette County, WI, Marquette County, WI, Richland County, WI, Rock County, WI, Sauk County, WI

The radar

The Quad Cities radar (KDVN), 128 km from the middle of the area, began a volume at 20:55 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

Davenport, (KDVN), launched 12:00Z, 8.9 hours before the alert went out and 126 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1257 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 80 m²/s²
0-3 km storm-relative helicity: 121 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 18, 12:49 PM CDT	Mesoscale Discussion	SPC	Adams, Brown, Bureau, Calhoun, Carroll, Cass and 33 more	116 min
Aug 18, 1:15 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Bond, Brown, Calhoun, Cass, Christian and 25 more	8 hr
Aug 18, 1:35 PM CDT	Tornado Watch	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 33 more	8 hr
Aug 18, 3:16 PM CDT	Mesoscale Discussion	SPC	Adams, Bond, Brown, Calhoun, Cass, Christian and 27 more	119 min
Aug 18, 6:35 PM CDT	Mesoscale Discussion	SPC	Alexander, Bond, Champaign, Christian, Clark, Clay and 41 more	115 min

Nearby

Mesoscale Discussions in Illinois, 2015 Mesoscale Discussions in Wisconsin, 2015 Mesoscale Discussions in Iowa, 2015 Every mesoscale discussion 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.