Details

• Date: 2023/01/28

• Observer: Chris Bilbrey
• Organization: Forecaster, CAIC

Location

• BC Zone: Northern San Juan
• Area Description: Expectation Mountain

Weather

• Ridgeline Wind Speed: 10-20 mph
• Ridgeline Wind Direction: SW
• Wind Loading: Light
• Sky Cover: Overcast
• Depth of New Snow: 2 in
• Most Significant Precip Rate: S-1 - < 1 cm/hr
• Weather Description: Windy, overcast day with brief periods of sun. Light snow showers (S-1) during the day did not amount to measurable accumulations. Southwest winds were moving snow onto easterly slopes near and above the treeline.

Snowpack

• Snowpack Description: Around 2 inches of new snow fell in the last 24 hours around 11,000 feet. This did not contribute to an increase in hazards at elevations. Steady winds recently formed 4 to 5-inch, 1F hard slabs below ridgelines on easterly slopes. These were stubborn to ski pressure and no cracking observed while jumping on pillowy surfaces on small test slopes. West and northwest slopes at treeline and slightly lower were wind-effected within the top 100 feet of ridgetops with large wind swells and harder surfaces. Below that, the snow was moderately dense wind-drifted snow with a creamy finish. Probing on west through north to east-facing slopes at the treeline and lower, we only felt subtle changes in snow layers from more recent storms. On west and east aspects, we found a 1 cm crust with a thin layer of facets below that was unreactive in quick pits. This layer was down around 30 cm. On northerly slopes, we found a 2 cm layer of small near-surface facets that produced moderate shear failures and hard force break failures in Compression Test. This layer was down around 40 cm. These varying interfaces likely need a bigger new snow load to become reactive, or a slope where fresh drifting is a bit deeper. Total height of snow on southerly slopes ranged 140 to 170 cm, was around 195 cm on northerlies below the treeline, and around 215 to 225 cm on northerlies near the treeline. The caveat, shallower and more variable snow depths do exists in rockier, steeper terrain at higher elevations. Persistent weak layers (11/29 FC) we targeted while probing ranged from about 145 to 175 cm below, with a stout mid-pack slab above. The bottom 20 to 40 cm of the snowpack structure consist of weaker/ softer snow grains (we did not dig to basal layers). A breakable zipper crust was found on most sunny slopes, but cool air temperatures were limiting crust thickness the higher we climbed.

Avalanches

	Date	Location/Path	#	Elev	Asp	Type	Trig	SizeR	SizeD
	2023/01/18  †		1	>TL	E	HS	N	R2	D2
Date: 2023/01/18 (Estimated) Observer: Chris Bilbrey Organization: Forecaster, CAIC Area Description: Expectation Mountain Elevation: 11900 ft Sliding Surface: O - Within Old Snow Maximum Vertical: 800 ft Comments: Suspect this slide ran around the same time as the Dolores Mountain slide across the valley.

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