Details

• Date: 2015/11/23

• Observer: Brian, Joe - Lazar, Messina
• Organization: Forecaster, CAIC

Location

• BC Zone: Front Range
• Area Description: Mt. Trelease, north of I-70 and northeast of Loveland ski area.
• Route Description: Parked at Dry Gulch TH. Toured up SE aspect of Mt Trelease up to ENE aspect of Mt. Trelease, took a snowpit observation. Continued around to NE aspect, found a large hard slab avalanche. Descended NE aspect to Dry Gulch drainage, back to trucks.

Weather

• Ridgeline Wind Speed: 5-10 mph
• Ridgeline Wind Direction: SW
• Wind Loading: Previous
• Temperature: 25 F
• Sky Cover: Clear
• Depth of Total Snow: 120 cm
• Weather Description: Clear day with calm to light winds gusting to moderate on ridgeline. No precip. HS varied significantly with wind distributed snow.

Snowpack

• Snowpack Description: Snowpack exhibited high strength/poor structure setup typically associated with a Persistent Slab avalanche problem. No results on a standard ECT test. ECT failure did occur deep in the snowpack when the top 40 cm was removed (see video). Surface slabs are stiffening on all aspects. Wind effects have reached down below treeline. Slabs below treeline are becoming less isolated and more specific.

Snowpack Obsvervation #1 Cracking: None Collapsing: None Persistent Weak Layer: Yes Comments: ENE aspect above treeline. HS= 142 cm but highly variable with lots of deep drifts separating bare ground. Snowpack consisted of 2 mm rounding depth hoar at the bottom, fist hardness. There was a decomposing crust above the depth hoar layer. Above the crust was about 70 cm of 1F to pencil hardness rounds and rounding facets. The top 40 cm consisted of 4F hardness decomposing new snow. No results on standard ECT test.

Avalanches

• Avalanche Description: Avalanche located on NE aspect of Mt. Trelease above treeline. This avalanche is visible from Herman Gulch Trailhead. Most likely ran on November 21. Skier triggered on shallow part of slab (1-2 ft thick). Appears to have started on crust-facet combo and stepped down to basal depth hoar layer, pulling out to the ground. Similar to results in snowpack tests.

	Date	Location/Path	#	Elev	Asp	Type	Trig	SizeR	SizeD
	2015/11/23  †	Dry Gulch	1	>TL	NE	HS	AS / u	R3	D2
Date: 2015/11/23 (Estimated) Observer: Brian, Joe - Lazar, Messina Organization: Forecaster, CAIC Area Description: NE face of Mt. Trelease Landmark: Dry Gulch Maximum Slope Angle: 35 ° Elevation: 12200 ft Sliding Surface: G - At Ground/Ice/Firm Weak Layer: Layer Weak Layer Grain Type: Depth Hoar Average Crown: 36 in Maximum Crown: 60 in Average Width: 300 ft Average Vertical: 200 ft Maximum Vertical: 300 ft Comments: We found a ski track entering at thin area of slab. No evidence of anyone caught in the avalanche.

Media

Video

Avalanche and snowpack conditions in Dry Gulch 11.23.15

Images