Alert archive / South Dakota / Mesoscale Discussions in 2013

Mesoscale Discussion 684

May 18, 20134 states

The Storm Prediction Center issued this mesoscale discussion at May 18, 2013, 8:33 PM CDT for 4 states. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued: May 18, 2013, 8:33 PM CDT (01:33 UTC)
Expired: May 18, 2013, 10:30 PM CDT
In force: 117 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 60 counties

Adams County, IA, Cass County, IA, Cherokee County, IA, Crawford County, IA, Fremont County, IA, Harrison County, IA, Ida County, IA, Lyon County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, O'Brien County, IA, Osceola County, IA, Page County, IA, Plymouth County, IA, Pottawattamie County, IA, Shelby County, IA, Sioux County, IA, Woodbury County, IA, Nobles County, MN, Rock County, MN, Burt County, NE, Cass County, NE, Cedar County, NE, Colfax County, NE, Cuming County, NE, Dakota County, NE, Dixon County, NE, Dodge County, NE, Douglas County, NE, Knox County, NE, Nemaha County, NE, Otoe County, NE, Pierce County, NE, Sarpy County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, Aurora County, SD, Bon Homme County, SD, Brule County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Sanborn County, SD, Tripp County, SD, Turner County, SD, Union County, SD, Yankton County, SD

The radar

The Sioux Falls radar (KFSD), 128 km from the middle of the area, began a volume at 01:34 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.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.6 hours before the alert went out and 177 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: 1935 J/kg
Mixed-layer CIN: -202 J/kg
Mixed-layer LCL: 1541 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 73 m²/s²
0-3 km storm-relative helicity: 144 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.3

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 18, 9:26 PM CDT	Severe Thunderstorm Watch	SPC	Fremont, Harrison, Lyon, Mills, Monona, Montgomery and 6 more	5 hr
May 19, 1:48 AM CDT	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Buena Vista, Carroll, Cass and 17 more	87 min
May 19, 11:30 AM CDT	Mesoscale Discussion	SPC	Appanoose, Benton, Black Hawk, Boone, Bremer, Buchanan and 52 more	90 min
May 19, 1:10 PM CDT	Tornado Watch	SPC	Allamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 34 more	8 hr
May 19, 1:47 PM CDT	Tornado Watch	SPC	Fremont, Page	10 hr
May 19, 2:59 PM CDT	Tornado Watch	SPC	Adair, Adams, Appanoose, Audubon, Benton, Boone and 50 more	8 hr
May 19, 5:04 PM CDT	Mesoscale Discussion	SPC	Allamakee, Black Hawk, Bremer, Buchanan, Buena Vista, Butler and 28 more	56 min
May 18, 11:27 PM CDT	Mesoscale Discussion	SPC	Clay, Wilkin	63 min
May 18, 11:49 PM CDT	Severe Thunderstorm Watch	SPC	Clay, Norman, Wilkin	4 hr
May 19, 2:32 AM CDT	Mesoscale Discussion	SPC	Clay, Norman, Wilkin	88 min
May 19, 5:25 PM CDT	Tornado Watch	SPC	Kanabec, Mille Lacs, Pine	5 hr
May 18, 7:29 PM CDT	Tornado Watch	SPC	Adams, Blaine, Boone, Boyd, Brown, Buffalo and 29 more	5 hr
May 18, 11:40 PM CDT	Mesoscale Discussion	SPC	Butler, Gage, Jefferson, Saline, Seward	35 min
May 19, 12:51 PM CDT	Mesoscale Discussion	SPC	Pawnee	114 min
May 19, 4:34 PM CDT	Mesoscale Discussion	SPC	Adams, Boone, Buffalo, Clay, Franklin, Garfield and 14 more	56 min
May 19, 4:50 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Antelope, Boone, Boyd, Buffalo, Burt and 33 more	5 hr
May 18, 10:14 PM CDT	Mesoscale Discussion	SPC	Bennett, Brown, Campbell, Corson, Custer, Dewey and 22 more	61 min
May 18, 11:59 PM CDT	Mesoscale Discussion	SPC	Brown, Edmunds, Faulk, Hand, Hyde, Spink	61 min

Nearby

Mesoscale Discussions in South Dakota, 2013 Mesoscale Discussions in Iowa, 2013 Mesoscale Discussions in Nebraska, 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.