Details

• Date: 2014/04/02

• Observer: Brian Lazar
• Organization: Forecast Staff, Colorado Avalanche Information Center

Location

• BC Zone: Front Range
• Area Description: RMNP. Emerald Lake. Dragon Tail Couloir

Weather

• Ridgeline Wind Speed: 10-20 mph
• Ridgeline Wind Direction: W
• Wind Loading: Moderate
• Temperature: 27 F
• Sky Cover: Overcast
• Depth of New Snow: 3 cm
• Depth of Total Snow: 200 cm
• Most Significant Precip Rate: S1 - 1 cm/hr
• Weather Description: warm, relatively calm/light winds for RMNP, light snow from 9 to 1pm (accumulations of 2-3 inches). Snow blowing around in chaotic patterns and loading a variety of slopes near and above treeline

Snowpack

• Snowpack Description: Deep and generally well consolidated snowpack beneath recent storm snow. The recent storm snow has settled to about 20-30cm. Thus dust is evident, but not as a distinct layer, but rather is diffuse in the lower 10cm or so of the recent storm snow. The storm snow rests on crusts (supportable in most places) on S and E aspects, wind polished surface near and above treeline, and over facets in protect north facing terrain BTL. Wind Slabs still an issue today. Loading continues. Slabs around a foot thick and 4F to 1F. Lots of cracking around skis, and easy to shed the slabs off the lower crusts on slope steeper than 35 degrees. Slabs are generally 10-12" thick, 10 to 30 feet across.

Avalanches

• Avalanche Description: while climbing the left flank along the rock wall of the couloir a natural wind slab released from a couple hundred feet above us. The slide was about 1 foot thick, 30 feet across, and ran 800 vertical feet due to steep terrain. It ran by us of to our right a bit. The slab broke about 200 feet below the ridgeline low in the start zone in a surprising place (not the steepest part of the couloir and lower down than would of expected). I think we underestimated the extent of wind loading going on higher up, even though there was only a few inches of new snow to blow around. But the sheltered couloir captured more wind loaded snow than anticipated is our hindsight conclusion.

	Date	Location/Path	#	Elev	Asp	Type	Trig	SizeR	SizeD
	2014/04/02	Rocky Mountain National Park	1	>TL	SE	SS	N	R2	D1.5
Date: 2014/04/02 Observer: Brian Lazar Organization: Forecast Staff, Colorado Avalanche Information Center Area Description: Dragon Tail Couloir Landmark: Rocky Mountain National Park Average Slope Angle: 40 ° Maximum Slope Angle: 45 ° Elevation: 12000 ft Sliding Surface: I - New/Old Interface Weak Layer: Interface Weak Layer Grain Type: Precipitation Particles Average Crown: 12 in Maximum Crown: 16 in Average Width: 30 ft Maximum Width: 50 ft Average Vertical: 800 ft
	2014/04/02  †	Rocky Mountain National Park	2	TL	SE	SS	AS / c	R1	D1
Date: 2014/04/02 (Estimated) Observer: Brian Lazar Organization: Forecast Staff, Colorado Avalanche Information Center Area Description: Dragon Tail Couloir Landmark: Rocky Mountain National Park Average Slope Angle: 40 ° Maximum Slope Angle: 45 ° Elevation: 11900 ft Average Crown: 10 in Maximum Crown: 12 in Average Width: 10 ft Maximum Width: 15 ft Average Vertical: 100 ft Maximum Vertical: 150 ft Comments: easy to shed small wind slabs with ski cuts in upper portion of slope

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