Alert archive / Illinois / Mesoscale Discussions in 2012

Mesoscale Discussion 703

May 4, 20124 states

The Storm Prediction Center issued this mesoscale discussion at May 4, 2012, 7:57 PM CDT for 4 states. It was in force for 63 min.

The area

The outline as issued.

The facts

Issued: May 4, 2012, 7:57 PM CDT (00:57 UTC)
Expired: May 4, 2012, 9:00 PM CDT
In force: 63 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 44 counties

Bond County, IL, Calhoun County, IL, Christian County, IL, Clay County, IL, Clinton County, IL, Crawford County, IL, Cumberland County, IL, Edwards County, IL, Effingham County, IL, Fayette County, IL, Franklin County, IL, Gallatin County, IL, Greene County, IL, Hamilton County, IL, Jasper County, IL, Jefferson County, IL, Jersey County, IL, Lawrence County, IL, Macoupin County, IL, Madison County, IL, Marion County, IL, Montgomery County, IL, Morgan County, IL, Richland County, IL, Saint Clair County, IL, Sangamon County, IL, Shelby County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Daviess County, IN, Dubois County, IN, Gibson County, IN, Knox County, IN, Pike County, IN, Posey County, IN, Spencer County, IN, Vanderburgh County, IN, Warrick County, IN, Daviess County, KY, Henderson County, KY, Union County, KY, City of Saint Louis, MO

The radar

The Evansville,IN radar (KVWX), 79 km from the middle of the area, began a volume at 01:01 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 243May 4, 10:35 PM CDT

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 1.0 hours before the alert went out and 164 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: 188 J/kg
Mixed-layer CIN: -108 J/kg
Mixed-layer LCL: 1330 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: -3 m²/s²
0-3 km storm-relative helicity: 155 m²/s²
Significant tornado parameter: -0.0
Supercell composite: -0.1

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
May 4, 10:18 PM CDT	Mesoscale Discussion	SPC	Bond, Calhoun, Clinton, Franklin, Greene, Hamilton and 11 more	87 min
May 4, 10:35 PM CDT	Severe Thunderstorm Watch	SPC	Bond, Calhoun, Clinton, Edwards, Fayette, Franklin and 24 more	8 hr
May 5, 12:55 AM CDT	Mesoscale Discussion	SPC	Edwards, Gallatin, Hamilton, Hardin, Saline, Wabash and 1 more	95 min
May 5, 5:06 AM CDT	Mesoscale Discussion	SPC	Gallatin, Hardin, White	114 min
May 5, 2:49 AM CDT	Severe Thunderstorm Watch	SPC	Posey, Spencer, Vanderburgh, Warrick	4 hr

Nearby

Mesoscale Discussions in Illinois, 2012 Mesoscale Discussions in Indiana, 2012 Mesoscale Discussions in Kentucky, 2012 Every mesoscale discussion in 2012

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.