Alert archive / Michigan / Mesoscale Discussions in 2013

Mesoscale Discussion 1803

August 30, 20135 counties in Illinois; 35 counties in Michigan; 17 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2013, 12:24 PM CDT for 5 counties in Illinois; 35 counties in Michigan; 17 counties in Wisconsin. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 30, 2013, 12:24 PM CDT (17:24 UTC)
Expired: Aug 30, 2013, 2:30 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 57 counties

Boone County, IL, Lake County, IL, McHenry County, IL, Stephenson County, IL, Winnebago County, IL, Allegan County, MI, Arenac County, MI, Barry County, MI, Bay County, MI, Clare County, MI, Clinton County, MI, Eaton County, MI, Genesee County, MI, Gladwin County, MI, Gratiot County, MI, Huron County, MI, Ingham County, MI, Ionia County, MI, Isabella County, MI, Kent County, MI, Lake County, MI, Lapeer County, MI, Livingston County, MI, Macomb County, MI, Mason County, MI, Mecosta County, MI, Midland County, MI, Montcalm County, MI, Muskegon County, MI, Newaygo County, MI, Oakland County, MI, Oceana County, MI, Osceola County, MI, Ottawa County, MI, Saginaw County, MI, Saint Clair County, MI, Sanilac County, MI, Shiawassee County, MI, Tuscola County, MI, Van Buren County, MI, Columbia County, WI, Dane County, WI, Dodge County, WI, Fond du Lac County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Kenosha County, WI, Lafayette County, WI, Milwaukee County, WI, Ozaukee County, WI, Racine County, WI, Rock County, WI, Sheboygan County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI

The radar

The Grand Rapids radar (KGRR), 26 km from the middle of the area, began a volume at 17:25 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 504Aug 30, 2:10 PM CDT

The nearest sounding before it

Green Bay/Straub, WI (KGRB), launched 12:00Z, 5.4 hours before the alert went out and 274 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: 1815 J/kg
Mixed-layer CIN: -70 J/kg
Mixed-layer LCL: 723 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 218 m²/s²
0-3 km storm-relative helicity: 235 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 12.5

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 30, 2:07 PM CDT	Severe Thunderstorm Watch	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 14 more	7 hr
Aug 30, 5:14 PM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 14 more	61 min
Aug 29, 7:30 PM CDT	Mesoscale Discussion	SPC	Gogebic	90 min
Aug 29, 11:57 PM CDT	Mesoscale Discussion	SPC	Gogebic	93 min
Aug 29, 8:20 PM CDT	Tornado Watch	SPC	Ashland, Barron, Bayfield, Brown, Burnett, Calumet and 30 more	5 hr

Nearby

Mesoscale Discussions in Michigan, 2013 Mesoscale Discussions in Wisconsin, 2013 Mesoscale Discussions in Illinois, 2013 Every mesoscale discussion in 2013

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.