Alert archive / South Dakota / Mesoscale Discussions in 2018

Mesoscale Discussion 440

May 17, 20185 states

The Storm Prediction Center issued this mesoscale discussion at May 17, 2018, 12:58 PM MDT for 5 states. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: May 17, 2018, 12:58 PM MDT (18:58 UTC)
Expired: May 17, 2018, 2:30 PM MDT
In force: 92 min
Issued by: the Storm Prediction Center
Chance of a watch: 95%

All 36 counties

Carter County, MT, Adams County, ND, Bowman County, ND, Hettinger County, ND, Slope County, ND, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Garden County, NE, Grant County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Bennett County, SD, Butte County, SD, Corson County, SD, Custer County, SD, Fall River County, SD, Haakon County, SD, Harding County, SD, Jackson County, SD, Lawrence County, SD, Meade County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Ziebach County, SD, Crook County, WY, Goshen County, WY, Laramie County, WY, Niobrara County, WY, Platte County, WY, Weston County, WY

The radar

The Rapid City radar (KUDX), 58 km from the middle of the area, began a volume at 18:58 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 (KRAP), launched 12:00Z, 7.0 hours before the alert went out and 51 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: 975 J/kg
Mixed-layer CIN: -186 J/kg
Mixed-layer LCL: 2104 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: -27 m²/s²
0-3 km storm-relative helicity: -53 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 17, 1:23 PM MDT	Severe Thunderstorm Watch	SPC	Carter	10 hr
May 17, 4:54 PM MDT	Mesoscale Discussion	SPC	Carter	66 min
May 17, 4:19 PM MDT	Mesoscale Discussion	SPC	Arthur, Banner, Box Butte, Chase, Cheyenne, Dawes and 10 more	116 min
May 17, 4:57 PM MDT	Severe Thunderstorm Watch	SPC	Arthur, Banner, Box Butte, Chase, Cherry, Cheyenne and 13 more	6 hr
May 17, 2:47 PM MDT	Mesoscale Discussion	SPC	Dickey, Emmons, McIntosh	28 min
May 17, 3:03 PM MDT	Severe Thunderstorm Watch	SPC	Dickey, Emmons, McIntosh, Sioux	6 hr

Nearby

Mesoscale Discussions in South Dakota, 2018 Mesoscale Discussions in Nebraska, 2018 Mesoscale Discussions in Wyoming, 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.