Alert archive / South Dakota / Mesoscale Discussions in 2013

Mesoscale Discussion 677

May 18, 201327 counties in South Dakota; Crook County, Weston County, Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 18, 2013, 2:31 PM MDT for 27 counties in South Dakota; Crook County, Weston County, Wyoming. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued: May 18, 2013, 2:31 PM MDT (20:31 UTC)
Expired: May 18, 2013, 3:30 PM MDT
In force: 59 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 29 counties

Bennett County, SD, Brule County, SD, Buffalo County, SD, Butte County, SD, Custer County, SD, Dewey County, SD, Fall River County, SD, Haakon County, SD, Hand County, SD, Hughes County, SD, Hyde County, SD, Jackson County, SD, Jones County, SD, Lawrence County, SD, Lyman County, SD, Meade County, SD, Mellette County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Todd County, SD, Tripp County, SD, Walworth County, SD, Ziebach County, SD, Crook County, WY, Weston County, WY

The radar

The Rapid City radar (KUDX), 74 km from the middle of the area, began a volume at 20:34 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

Rapid City, SD (KUNR), launched 12:00Z, 8.5 hours before the alert went out and 76 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: 277 J/kg
Mixed-layer CIN: -205 J/kg
Mixed-layer LCL: 922 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: -2 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 17, 6:28 PM MDT	Mesoscale Discussion	SPC	Bennett, Brule, Butte, Custer, Fall River, Gregory and 15 more	92 min
May 17, 6:59 PM MDT	Severe Thunderstorm Watch	SPC	Aurora, Brule, Buffalo, Charles Mix, Douglas, Faulk and 10 more	3 hr
May 17, 9:26 PM MDT	Mesoscale Discussion	SPC	Aurora, Bennett, Brule, Buffalo, Butte, Charles Mix and 23 more	64 min
May 18, 2:55 PM MDT	Severe Thunderstorm Watch	SPC	Bennett, Butte, Custer, Fall River, Haakon, Harding and 9 more	8 hr
May 18, 4:24 PM MDT	Mesoscale Discussion	SPC	Brown, Campbell, Corson, Dewey, Edmunds, Faulk and 10 more	66 min
May 18, 4:46 PM MDT	Severe Thunderstorm Watch	SPC	Brown, Buffalo, Campbell, Corson, Dewey, Edmunds and 12 more	7 hr
May 18, 5:11 PM MDT	Mesoscale Discussion	SPC	Brookings, Codington, Deuel, Grant, Hamlin, Kingsbury	94 min

Nearby

Mesoscale Discussions in South Dakota, 2013 Mesoscale Discussions in Wyoming, 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.