Alert archive / North Dakota / Mesoscale Discussions in 2014

Mesoscale Discussion 1587

August 20, 201411 counties in North Dakota; 10 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2014, 2:42 PM MDT for 11 counties in North Dakota; 10 counties in South Dakota. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 20, 2014, 2:42 PM MDT (20:42 UTC)
Expired: Aug 20, 2014, 4:45 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 21 counties

Adams County, ND, Burleigh County, ND, Emmons County, ND, Grant County, ND, Hettinger County, ND, McIntosh County, ND, Mercer County, ND, Morton County, ND, Oliver County, ND, Sioux County, ND, Stark County, ND, Campbell County, SD, Corson County, SD, Dewey County, SD, Edmunds County, SD, Perkins County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Walworth County, SD, Ziebach County, SD

The radar

The Bismarck radar (KBIS), 93 km from the middle of the area, began a volume at 20:41 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 469Aug 20, 4:00 PM MDT

The nearest sounding before it

Bismarck Municip, ND (KBIS), launched 12:00Z, 8.7 hours before the alert went out and 95 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: 756 J/kg
Mixed-layer CIN: -264 J/kg
Mixed-layer LCL: 1501 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 13 m²/s²
0-3 km storm-relative helicity: 76 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

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 20, 4:00 PM MDT	Severe Thunderstorm Watch	SPC	Adams, Burleigh, Emmons, Grant, Hettinger, Kidder and 4 more	7 hr
Aug 20, 1:40 AM MDT	Mesoscale Discussion	SPC	Bon Homme, Charles Mix, Clay, Douglas, Hutchinson, Union and 1 more	2 hr

Nearby

Mesoscale Discussions in North Dakota, 2014 Mesoscale Discussions in South Dakota, 2014 Every mesoscale discussion in 2014

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.