Problem #1: Storm Snow
Location: All aspects and elevations. Large amounts of new snow have fallen in the last week (22"-41") onto a thin rain crust that is now buried between 2 and 4 feet deep. The new snow did bond well to this crust, making large skier triggered avalanches possible at the interface between the old and new snow.
In addition, fluctuating winds and temperatures during the storm created reactive layers within the new snow that are also reactive to human triggers. Any further new snow Thursday and Friday will only add more stress and new storm layers. Don't be lured into steep terrain by the promise of powder. Give these layers time to adjust to the new load and gain strength before venturing into avalanche terrain.
Problem #2: Wind Slab
Location: All aspects at and above treeline. Shifting winds out of the North and South have loaded all aspects of the compass with wind slabs of varying thickness and reactivity. Most recently, winds on Wednesday blew out of the South at 15-25mph, loading the northern half of the compass rose. Wind slab can be identified by dense, cohesive snow, cracking, and a hollow or drum like feel. Look for wind slab in top and cross loaded terrain like below ridge lines and along gullies. These avalanches could lure riders well on to the slab before failing and could be surprisingly large.
There was a human-triggered D2 avalanche on White Pass Dec 16th, with remote triggering and a crown depth of 3-4ft, on a wind-loaded northeast aspect at 1500m. One person was caught and buried to their waist/chest.
Sporadic natural storm slab avalanches were observed from the last week, size D2-D3 on wind loaded lee aspects and gullies (above 3000ft). Crowns were around 60-90cm thick.
An additinal 3-6" of snow is likely through Thursday, with snow levels remaining at sea level. Clearing and cooler weather with increasing north winds will begin Friday evening and last for several days.
( *star means meteorological estimate )
If you get out riding, please send in an observation!
Start the season with fresh batteries in your beacon, and do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM.
Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.
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