Alert archive / Wyoming / Mesoscale Discussions in 2018

Mesoscale Discussion 997

July 3, 2018Big Horn County, Carter County, Powder River County, Montana; Lawrence County, South Dakota; 7 counties in Wyoming

The Storm Prediction Center issued this mesoscale discussion at Jul 3, 2018, 2:25 PM MDT for Big Horn County, Carter County, Powder River County, Montana; Lawrence County, South Dakota; 7 counties in Wyoming. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 3, 2018, 2:25 PM MDT (20:25 UTC)
Expired: Jul 3, 2018, 4:30 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Big Horn County, MT, Carter County, MT, Powder River County, MT, Lawrence County, SD, Campbell County, WY, Converse County, WY, Crook County, WY, Johnson County, WY, Niobrara County, WY, Sheridan County, WY, Weston County, WY

The radar

The Riverton/Lander radar (KRIW), 238 km from the middle of the area, began a volume at 20:27 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 259Jul 3, 4:40 PM MDT

The nearest sounding before it

Rapid City, SD (KRAP), launched 12:00Z, 8.4 hours before the alert went out and 248 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: 114 J/kg
Mixed-layer CIN: -531 J/kg
Mixed-layer LCL: 2085 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 18 m²/s²
0-3 km storm-relative helicity: 145 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 2, 6:59 PM MDT	Severe Thunderstorm Watch	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Rosebud and 2 more	6 hr
Jul 2, 8:50 PM MDT	Mesoscale Discussion	SPC	Big Horn, Carter, Custer, Fallon, Powder River, Rosebud and 2 more	115 min
Jul 2, 11:01 PM MDT	Mesoscale Discussion	SPC	Carter, Custer, Fallon, Powder River	89 min
Jul 3, 4:42 PM MDT	Severe Thunderstorm Watch	SPC	Carter	7 hr
Jul 2, 6:36 PM MDT	Severe Thunderstorm Watch	SPC	Brown, Campbell, Clark, Codington, Corson, Day and 11 more	9 hr
Jul 2, 10:32 PM MDT	Mesoscale Discussion	SPC	Clark, Codington, Deuel, Grant, Hamlin, Roberts and 1 more	88 min
Jul 3, 12:59 AM MDT	Severe Thunderstorm Watch	SPC	Brown, Campbell, Clark, Codington, Corson, Day and 11 more	7 hr
Jul 3, 3:15 AM MDT	Mesoscale Discussion	SPC	Brown, Campbell, Clark, Codington, Corson, Day and 10 more	90 min
Jul 3, 6:01 AM MDT	Mesoscale Discussion	SPC	Brown, Campbell, McPherson, Marshall, Roberts	119 min
Jul 3, 5:16 PM MDT	Mesoscale Discussion	SPC	Beadle, Brookings, Brown, Campbell, Clark, Codington and 17 more	2 hr
Jul 3, 5:42 PM MDT	Severe Thunderstorm Watch	SPC	Brown, Clark, Day, Edmunds, Faulk, Hand and 8 more	4 hr

Nearby

Mesoscale Discussions in Wyoming, 2018 Mesoscale Discussions in Montana, 2018 Mesoscale Discussions in South Dakota, 2018 Every mesoscale discussion in 2018

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.