Alert archive / Illinois / Mesoscale Discussions in 2015

Mesoscale Discussion 1707

August 18, 201533 counties in Illinois; 20 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2015, 3:16 PM CDT for 33 counties in Illinois; 20 counties in Missouri. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Aug 18, 2015, 3:16 PM CDT (20:16 UTC)
Expired: Aug 18, 2015, 5:15 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center

All 53 counties

Adams County, IL, Bond County, IL, Brown County, IL, Calhoun County, IL, Cass County, IL, Christian County, IL, Clinton County, IL, DeWitt County, IL, Effingham County, IL, Fayette County, IL, Greene County, IL, Jersey County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Mason County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Perry County, IL, Piatt County, IL, Pike County, IL, Randolph County, IL, Saint Clair County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Shelby County, IL, Washington County, IL, City of Saint Louis, MO, Crawford County, MO, Franklin County, MO, Gasconade County, MO, Iron County, MO, Jefferson County, MO, Lincoln County, MO, Madison County, MO, Marion County, MO, Montgomery County, MO, Perry County, MO, Pike County, MO, Ralls County, MO, Reynolds County, MO, Saint Charles County, MO, Saint Francois County, MO, Saint Louis County, MO, Sainte Genevieve County, MO, Warren County, MO, Washington County, MO

The radar

The St Louis radar (KLSX), 78 km from the middle of the area, began a volume at 20:16 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, 8.3 hours before the alert went out and 163 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: 949 J/kg
Mixed-layer CIN: -51 J/kg
Mixed-layer LCL: 802 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 85 m²/s²
0-3 km storm-relative helicity: 70 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, 3:53 PM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, DeKalb, Henderson, Henry and 16 more	2 hr
Aug 18, 6:35 PM CDT	Mesoscale Discussion	SPC	Alexander, Bond, Champaign, Christian, Clark, Clay and 41 more	115 min
Aug 18, 2:11 PM CDT	Mesoscale Discussion	SPC	Bates, Buchanan, Cass, Clay, Clinton, Jackson and 1 more	3 hr
Aug 18, 3:06 PM CDT	Severe Thunderstorm Watch	SPC	Andrew, Barton, Bates, Buchanan, Cass, Clay and 11 more	7 hr
Aug 18, 5:15 PM CDT	Mesoscale Discussion	SPC	Audrain, Barton, Bates, Benton, Boone, Buchanan and 38 more	90 min

Nearby

Mesoscale Discussions in Illinois, 2015 Mesoscale Discussions in Missouri, 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.