Alert archive / Montana / Mesoscale Discussions in 2011

Mesoscale Discussion 1857

August 4, 201110 counties in Montana; 10 counties in North Dakota

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2011, 2:24 PM MDT for 10 counties in Montana; 10 counties in North Dakota. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Aug 4, 2011, 2:24 PM MDT (20:24 UTC)
Expired: Aug 4, 2011, 4:00 PM MDT
In force: 96 min
Issued by: the Storm Prediction Center

Counties Custer County, MT, Dawson County, MT, Fallon County, MT, Garfield County, MT, McCone County, MT, Prairie County, MT, Richland County, MT, Rosebud County, MT, Treasure County, MT, Wibaux County, MT, Adams County, ND, Billings County, ND, Bowman County, ND, Dunn County, ND, Golden Valley County, ND, Hettinger County, ND, McKenzie County, ND, Mercer County, ND, Slope County, ND, Stark County, ND

The radar

The Glasgow radar (KGGW), 213 km from the middle of the area, began a volume at 20:24 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 728Aug 4, 4:50 PM MDT

The nearest sounding before it

Bismarck Municip, ND (KBIS), launched 12:00Z, 8.4 hours before the alert went out and 298 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: 405 J/kg
Mixed-layer CIN: -228 J/kg
Mixed-layer LCL: 1353 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 30 m²/s²
0-3 km storm-relative helicity: -77 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 4, 4:49 PM MDT	Severe Thunderstorm Watch	SPC	Dawson, Fallon, Prairie, Richland, Wibaux	5 hr

Nearby

Mesoscale Discussions in Montana, 2011 Mesoscale Discussions in North Dakota, 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.