Alert archive / South Dakota / Mesoscale Discussions in 2004

Mesoscale Discussion 390

April 20, 2004Boyd County, Keya Paha County, Nebraska; 8 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2004, 12:05 PM CDT for Boyd County, Keya Paha County, Nebraska; 8 counties in South Dakota. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Apr 20, 2004, 12:05 PM CDT (17:05 UTC)
Expired: Apr 20, 2004, 1:30 PM CDT
In force: 85 min
Issued by: the Storm Prediction Center

Counties Boyd County, NE, Keya Paha County, NE, Bennett County, SD, Gregory County, SD, Jackson County, SD, Jones County, SD, Lyman County, SD, Mellette County, SD, Todd County, SD, Tripp County, SD

The radar

The North Platte radar (KLNX), 175 km from the middle of the area, began a volume at 17:26 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 12:00Z, 5.1 hours before the alert went out and 267 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1275 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: -304 m²/s²
0-3 km storm-relative helicity: -332 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
Apr 20, 5:12 PM CDT	Mesoscale Discussion	SPC	Antelope, Boone, Garfield, Holt, Knox, Madison and 5 more	3 hr
Apr 20, 6:25 PM CDT	Severe Thunderstorm Watch	SPC	Antelope, Boone, Burt, Butler, Cass, Cedar and 20 more	5 hr

Nearby

Mesoscale Discussions in South Dakota, 2004 Mesoscale Discussions in Nebraska, 2004 Every mesoscale discussion in 2004

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.