Alert archive / South Dakota / Mesoscale Discussions in 2007

Mesoscale Discussion 522

April 21, 2007Boyd County, Nebraska; 17 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2007, 1:31 AM CDT for Boyd County, Nebraska; 17 counties in South Dakota. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued: Apr 21, 2007, 1:31 AM CDT (06:31 UTC)
Expired: Apr 21, 2007, 2:30 AM CDT
In force: 59 min
Issued by: the Storm Prediction Center

Counties Boyd County, NE, Aurora County, SD, Beadle County, SD, Brule County, SD, Buffalo County, SD, Charles Mix County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hand County, SD, Hanson County, SD, Jerauld County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Miner County, SD, Sanborn County, SD, Tripp County, SD

The radar

The Sioux Falls radar (KFSD), 202 km from the middle of the area, began a volume at 06:33 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 nearest sounding before it

N. Platte/Lee Bi, NE (KLBF), launched 00:00Z, 6.5 hours before the alert went out and 293 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: 333 J/kg
Mixed-layer CIN: -161 J/kg
Mixed-layer LCL: 1187 m above ground
0-6 km bulk shear: 34 kt
0-1 km storm-relative helicity: 91 m²/s²
0-3 km storm-relative helicity: 120 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

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
Apr 20, 8:45 PM CDT	Severe Thunderstorm Watch	SPC	Blaine, Boyd, Brown, Chase, Cherry, Custer and 19 more	5 hr
Apr 21, 6:11 AM CDT	Mesoscale Discussion	SPC	Frontier, Hitchcock, Red Willow	2 hr
Apr 21, 1:35 PM CDT	Mesoscale Discussion	SPC	Arthur, Cherry, Deuel, Garden, Grant, Hooker and 5 more	55 min
Apr 21, 1:57 PM CDT	Tornado Watch	SPC	Arthur, Blaine, Boyd, Brown, Chase, Cherry and 24 more	9 hr
Apr 21, 3:10 PM CDT	Tornado Watch	SPC	Dundy, Hitchcock, Red Willow	7 hr
Apr 21, 5:57 PM CDT	Mesoscale Discussion	SPC	Arthur, Blaine, Boyd, Brown, Chase, Cherry and 23 more	2 hr
Apr 21, 6:10 PM CDT	Mesoscale Discussion	SPC	Dundy, Hitchcock, Red Willow	2 hr
Apr 20, 10:56 PM CDT	Mesoscale Discussion	SPC	Aurora, Beadle, Bennett, Brown, Brule, Buffalo and 27 more	2 hr
Apr 21, 2:30 PM CDT	Tornado Watch	SPC	Aurora, Beadle, Bon Homme, Brookings, Brown, Brule and 38 more	8 hr
Apr 21, 6:20 PM CDT	Mesoscale Discussion	SPC	Aurora, Beadle, Brown, Brule, Buffalo, Campbell and 32 more	115 min

Nearby

Mesoscale Discussions in South Dakota, 2007 Mesoscale Discussions in Nebraska, 2007 Every mesoscale discussion in 2007

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.