Alert archive / South Dakota / Mesoscale Discussions in 2011

Mesoscale Discussion 1865

August 5, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Aug 5, 2011, 12:05 PM MDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 5, 2011, 12:05 PM MDT (18:05 UTC)
Expired: Aug 5, 2011, 2:30 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 37 counties

Big Horn County, MT, Carter County, MT, Custer County, MT, Fallon County, MT, Powder River County, MT, Prairie County, MT, Rosebud County, MT, Wibaux County, MT, Adams County, ND, Billings County, ND, Bowman County, ND, Emmons County, ND, Golden Valley County, ND, Grant County, ND, Hettinger County, ND, Morton County, ND, Sioux County, ND, Slope County, ND, Stark County, ND, Butte County, SD, Campbell County, SD, Corson County, SD, Custer County, SD, Dewey County, SD, Haakon County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Pennington County, SD, Perkins County, SD, Walworth County, SD, Ziebach County, SD, Campbell County, WY, Crook County, WY, Johnson County, WY, Sheridan County, WY, Weston County, WY

The radar

The Rapid City radar (KUDX), 205 km from the middle of the area, began a volume at 18:04 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, 6.1 hours before the alert went out and 208 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: 1650 J/kg
Mixed-layer CIN: -38 J/kg
Mixed-layer LCL: 1019 m above ground
0-6 km bulk shear: 13 kt
0-1 km storm-relative helicity: -37 m²/s²
0-3 km storm-relative helicity: -16 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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 5, 2:55 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Rosebud and 1 more	5 hr
Aug 5, 4:25 PM MDT	Mesoscale Discussion	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Prairie and 2 more	2 hr
Aug 4, 6:40 PM MDT	Mesoscale Discussion	SPC	Adams, Billings, Bowman, Dunn, Golden Valley, Hettinger and 2 more	95 min
Aug 5, 12:48 PM MDT	Severe Thunderstorm Watch	SPC	Adams, Billings, Bowman, Burleigh, Dunn, Emmons and 12 more	7 hr
Aug 5, 5:26 PM MDT	Mesoscale Discussion	SPC	Burleigh, Dickey, Eddy, Emmons, Foster, Grant and 10 more	94 min

Nearby

Mesoscale Discussions in South Dakota, 2011 Mesoscale Discussions in North Dakota, 2011 Mesoscale Discussions in Montana, 2011 Every mesoscale discussion in 2011

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.