Alert archive / Illinois / Mesoscale Discussions in 2017

Mesoscale Discussion 720

May 15, 201715 counties in Illinois; 7 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at May 15, 2017, 5:52 PM CDT for 15 counties in Illinois; 7 counties in Wisconsin. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: May 15, 2017, 5:52 PM CDT (22:52 UTC)
Expired: May 15, 2017, 7:45 PM CDT
In force: 113 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 22 counties

Boone County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Jo Daviess County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Will County, IL, Winnebago County, IL, Dane County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Lafayette County, WI, Rock County, WI, Walworth County, WI

The radar

The Milwaukee radar (KMKX), 88 km from the middle of the area, began a volume at 22:55 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 watches that followed

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

Severe Thunderstorm Watch 217May 15, 7:55 PM CDT

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 10.9 hours before the alert went out and 134 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: 1352 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 98 m²/s²
0-3 km storm-relative helicity: 158 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
May 15, 5:11 PM CDT	Severe Thunderstorm Watch	SPC	Crawford, Grant, Richland	9 hr

Nearby

Mesoscale Discussions in Illinois, 2017 Mesoscale Discussions in Wisconsin, 2017 Every mesoscale discussion in 2017

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.