Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 203

April 2, 201827 counties in Illinois; Gibson County, Pike County, Posey County, Indiana; 5 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Apr 2, 2018, 10:46 PM CDT for 27 counties in Illinois; Gibson County, Pike County, Posey County, Indiana; 5 counties in Missouri. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Apr 2, 2018, 10:46 PM CDT (03:46 UTC)
Expired: Apr 3, 2018, 12:45 AM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 35 counties

Bond County, IL, Clay County, IL, Clinton County, IL, Edwards County, IL, Effingham County, IL, Fayette County, IL, Franklin County, IL, Hamilton County, IL, Jackson County, IL, Jefferson County, IL, Jersey County, IL, Lawrence County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Monroe County, IL, Montgomery County, IL, Perry County, IL, Randolph County, IL, Richland County, IL, Saint Clair County, IL, Saline County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Gibson County, IN, Pike County, IN, Posey County, IN, City of Saint Louis, MO, Jefferson County, MO, Saint Charles County, MO, Saint Louis County, MO, Warren County, MO

The radar

The St Louis radar (KLSX), 113 km from the middle of the area, began a volume at 03:46 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 00:00Z, 3.8 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-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: 1 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 549 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 233 m²/s²
0-3 km storm-relative helicity: 495 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
Apr 3, 12:57 PM CDT	Mesoscale Discussion	SPC	Alexander, Clay, Clinton, Edwards, Effingham, Fayette and 24 more	2 hr
Apr 3, 1:33 PM CDT	Tornado Watch	SPC	Alexander, Bond, Clark, Clay, Clinton, Coles and 34 more	7 hr
Apr 3, 3:34 PM CDT	Mesoscale Discussion	SPC	Alexander, Bond, Clay, Clinton, Coles, Crawford and 32 more	86 min
Apr 3, 11:41 AM CDT	Mesoscale Discussion	SPC	Bartholomew, Blackford, Brown, Clark, Clay, Crawford and 46 more	3 hr
Apr 3, 12:16 PM CDT	Tornado Watch	SPC	Bartholomew, Boone, Brown, Clark, Clay, Crawford and 48 more	6 hr
Apr 3, 3:18 PM CDT	Mesoscale Discussion	SPC	Clark, Dearborn, Decatur, Fayette, Floyd, Franklin and 9 more	117 min
Apr 3, 6:30 PM CDT	Tornado Watch	SPC	Bartholomew, Boone, Brown, Clark, Clay, Crawford and 41 more	5 hr

Nearby

Mesoscale Discussions in Illinois, 2018 Mesoscale Discussions in Missouri, 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.