Alert archive / Montana / Mesoscale Discussions in 2005

Mesoscale Discussion 934

May 20, 20058 counties in Montana; Big Horn County, Park County, Sheridan County, Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 20, 2005, 2:31 PM MDT for 8 counties in Montana; Big Horn County, Park County, Sheridan County, Wyoming. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: May 20, 2005, 2:31 PM MDT (20:31 UTC)
Expired: May 20, 2005, 4:00 PM MDT
In force: 89 min
Issued by: the Storm Prediction Center

Counties Big Horn County, MT, Carbon County, MT, Gallatin County, MT, Golden Valley County, MT, Park County, MT, Stillwater County, MT, Sweet Grass County, MT, Yellowstone County, MT, Big Horn County, WY, Park County, WY, Sheridan County, WY

The radar

The Billings radar (KBLX), 54 km from the middle of the area, began a volume at 20:33 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 303May 20, 4:20 PM MDT

The nearest sounding before it

Great_falls, MT (KTFX), launched 12:00Z, 8.5 hours before the alert went out and 264 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: 2337 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: -69 m²/s²
0-3 km storm-relative helicity: 76 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, 4:20 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carbon, Custer, Golden Valley, Musselshell, Powder River and 6 more	7 hr

Nearby

Mesoscale Discussions in Montana, 2005 Mesoscale Discussions in Wyoming, 2005 Every mesoscale discussion in 2005

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.