Alert archive / Montana / Mesoscale Discussions in 2007

Mesoscale Discussion 843

May 20, 20078 counties in Montana; Butte County, Lawrence County, South Dakota; Campbell County, Crook County, Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 20, 2007, 6:48 PM MDT for 8 counties in Montana; Butte County, Lawrence County, South Dakota; Campbell County, Crook County, Wyoming. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: May 20, 2007, 6:48 PM MDT (00:48 UTC)
Expired: May 20, 2007, 8:15 PM MDT
In force: 87 min
Issued by: the Storm Prediction Center

Counties Big Horn County, MT, Carter County, MT, Custer County, MT, Powder River County, MT, Prairie County, MT, Rosebud County, MT, Treasure County, MT, Yellowstone County, MT, Butte County, SD, Lawrence County, SD, Campbell County, WY, Crook County, WY

The radar

The Rapid City radar (KUDX), 230 km from the middle of the area, began a volume at 00:48 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

Rapid City, SD (KUNR), launched 00:00Z, 0.8 hours before the alert went out and 229 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: 143 J/kg
Mixed-layer CIN: -272 J/kg
Mixed-layer LCL: 1880 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 58 m²/s²
0-3 km storm-relative helicity: 155 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
May 20, 10:03 PM MDT	Mesoscale Discussion	SPC	Custer, Dawson, Prairie, Wibaux	87 min
May 21, 12:07 PM MDT	Mesoscale Discussion	SPC	Roberts	83 min
May 21, 1:34 PM MDT	Mesoscale Discussion	SPC	Campbell, Corson, Dewey, Haakon, Hughes, Jackson and 13 more	86 min
May 21, 1:52 PM MDT	Severe Thunderstorm Watch	SPC	Bennett, Butte, Campbell, Corson, Custer, Dewey and 18 more	8 hr
May 21, 5:17 PM MDT	Mesoscale Discussion	SPC	Butte, Campbell, Corson, Custer, Dewey, Haakon and 9 more	88 min

Nearby

Mesoscale Discussions in Montana, 2007 Mesoscale Discussions in South Dakota, 2007 Mesoscale Discussions in Wyoming, 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.