Details

• Date: 2020/01/17

• Observer: Ben Pritchett, Bill Nalli and Ryan Lewthwaite
• Organization: Forecaster, CAIC

Location

• BC Zone: Gunnison
• Area Description: Mt. Emmons

Weather

• Ridgeline Wind Speed: 40+ mph
• Ridgeline Wind Direction: W
• Wind Loading: Intense
• Temperature: 16 F
• Depth of New Snow: 22 cm
• Depth of Total Snow: 140 cm
• Most Significant Precip Rate: S5 - 5 cm/hr
• Weather Description: S2-S5 all day, with unrelenting westerly winds. Visibility remained poor.

Snowpack

• Snowpack Description: Dangerous conditions developed by the afternoon. Soft, dense drifts up to 3 feet. The most dangerous snowpack we found was where 2-3 foot deep drifts built on buried melt-freeze crusts on southeasterly terrain near and below treeline (we didn't get above treeline). Easterly-facing slopes without crusts had more load (3+ feet deep drifts), but seemed less hair-trigger. We observed many slope-wide collapses where drifted snow overloaded thin crusts with facets below, or even just overloading weak faceted layers in the upper snowpack. We measured 2.5" SWE above a faceted crust on a lightly drifted slope at 11,400'. This 2.5" SWE is the 2020 snow total and the weakness below was formed in late December. This ~30 degree slope collapsed and cracked but was not quite steep enough to slide. This seemed to be theme for the afternoon as we travelled through 20-25 degree slopes with widespread and obvious signs of instability. We extrapolated that we would have been likely to trigger a large avalanches in more consequential terrain.

Avalanches

• Avalanche Description: Remote triggered one large slab avalanche. Crown depth was around 2' deep, but we were in lower angled terrain above and couldn't really see anything other than the crown since the terrain rolled out of sight below. Test slopes were easy to crack. Saw a couple of natural avalanches, but we could not make out how far they propagated in steep terrain because the visibility was too poor.

	Date	Location/Path	#	Elev	Asp	Type	Trig	SizeR	SizeD
	2020/01/17  †	Mount Emmons	1	TL	NE	SS	AS / r	R1	D2
Date: 2020/01/17 (Estimated) Observer: Ben Pritchett, Bill Nalli and Ryan Lewthwaite Organization: Forecaster, CAIC Area Description: Red Lady Bowl - sidewall near flat ridge on skin track Landmark: Mount Emmons Comments: Estimating size based on terrain feature, but visibility was too poor to actually see how far it ran.
	2020/01/17  †		2	TL	E	SS	N	R1	D1.5
Date: 2020/01/17 (Estimated) Observer: Ben Pritchett, Bill Nalli and Ryan Lewthwaite Organization: Forecaster, CAIC Comments: Estimating size - couldn't see how far it ran w/ poor visibility

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