Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 1484

September 20, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Sep 20, 2018, 3:16 PM CDT for 4 states. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Sep 20, 2018, 3:16 PM CDT (20:16 UTC)
Expired: Sep 20, 2018, 4:45 PM CDT
In force: 89 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 38 counties

Boone County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Whiteside County, IL, Will County, IL, Winnebago County, IL, DeKalb County, IN, Elkhart County, IN, Kosciusko County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Noble County, IN, Porter County, IN, Saint Joseph County, IN, Starke County, IN, Steuben County, IN, Allegan County, MI, Berrien County, MI, Branch County, MI, Calhoun County, MI, Cass County, MI, Hillsdale County, MI, Kalamazoo County, MI, Saint Joseph County, MI, Van Buren County, MI, Defiance County, OH, Fulton County, OH, Williams County, OH

The radar

The Chicago radar (KLOT), 98 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 235 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: 905 J/kg
Mixed-layer CIN: -78 J/kg
Mixed-layer LCL: 1217 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 97 m²/s²
0-3 km storm-relative helicity: 82 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

As transmitted.

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Nearby

Mesoscale Discussions in Illinois, 2018 Mesoscale Discussions in Indiana, 2018 Mesoscale Discussions in Michigan, 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.