Large, full-path natural avalanches will be possible Friday-Saturday. Avoid lower runout zones during this time.
Above 2,500ft High
1,500 to 2,500ft High
Below 1,500ft High
Degrees of Avalanche Danger ?
Avalanche Problem #1: Storm Slab
Heavy snowfall rates of 2-3″/hr during the storm, strong southerly winds, and over 3ocm of new (upside-down) snowfall will make natural and human-triggered slides likely Friday-Saturday. The new/old snow interface will provide a hard and slick bed surface for storm slabs to travel on. Wind-loaded slopes on lee aspects and terrain features will be especially dangerous. North-facing avalanche chutes may produce large avalanches, especially Friday afternoon-Saturday. Avoid lower runouts during this time.
Avalanche Problem #2: Wet Slides
This will be a concern only below 1,500ft after the transition to rain, which should occur sometime Friday afternoon. As heavy rain wets the new snow, expect wet sluffs and wet slabs to occur on slopes steeper than 32 degrees. Steep open areas and gullies/terrain traps will be dangerous during this period.
Avalanche Problem #3: Persistent Slab
Finally, there is a layer of large facets 60-90cm deep in this zone. Though it will be hard to trigger this layer, the very heavy new load of fresh snow will add a lot of stress. Avalanches at the surface may step down this deep, leading to wide and deep propagation. Avoiding rocky and thin areas will help minimize the risk of triggering this layer. Remote triggering is also possible on this layer, so stay out from below steep slopes.
Recent Avalanche Activity
There were isolated areas of wet and dry loose slides coming down from steep/cliffy terrain, mainly on sun-affected slopes. None of this activity was large, and occurred during warm temperatures earlier this week.
Snow totals from Thursday night are 6-15″ of low density snow (higher amounts in the Lutak zone). South winds were strong in the alpine.
A strong front will move in Friday with increasingly heavy precipitation and south winds. Snow levels will start at sea level, and rise to 1000-2000ft by Saturday morning. 2-3″ of liquid equivalent is expected Friday – Saturday night, adding up to 2-3 feet of upside-down snowfall, with around 1 foot below 1500ft.
Cold and very windy weather occurred from the 6th-10th. Temperatures were in the single digits, with north winds at 40-80mph in many alpine areas. During this time the snowpack became re-frozen, hard, and wind packed.
Additional Info & Media
2017 New Year’s resolution – develop backcountry habits to LIVE TO RIDE ANOTHER DAY:
- everyone in my riding group has a functioning beacon, probe, and shovel (& floatpack)
- my group chooses to avoid slopes with rocky trigger points
- my group chooses to avoid slopes with terrain traps; cliffs, gullies, and creek ravines
- my group agrees that one rider on a steep slope at a time is what we do
- my group gathers out of harm’s way, beyond the run-out
- my group reviews our day – where could we have triggered a slide? how can we improve our plan?