The Bottom Line: In areas with deep new snow, you may be able to easily trigger surface soft slabs. Use care to avoid terrain traps where even small surface slides can pile up deep. Deeper down, warming temperatures are adding stress to our persistent weak layers within the snowpack. The risk of deep, deadly avalanches remains, and you should exercise extra caution and keep a wide safety margin. Travel one at a time to minimize exposure to slopes 30 degrees and steeper. Stay clear of trigger points (thin areas, rocks, small trees) where you can easily trigger persistent weak layers. If you find a trigger point, the resulting crack will travel across slopes and trigger an avalanche in deeper areas.

Thoughts on Risk Reduction: A remote trigger observed at the Pass this week is a good indication of the increased stress on our weak layers. Hard slabs in the upper snowpack are protecting the weak layers beneath, making them hard to trigger. But we’ve seen strong, steady warming over the last week and a new load of heavy snowfall, both of which will increase the chances that your weight will tip the scales. Your best bet to avoid a deadly avalanche is to reign in your expectations and lower your risk tolerance. Keep a wider-than-usual margin of safety by sticking to low-angle terrain, and giving dangerous areas a wide berth. There will be times later this spring when you can be more ambitious with the terrain… this is not the time.

Midpack Melt Layers and Crusts:

There is a serious weak layer about 90cm deep (The “Big Warmup” Layer, Formed Nov 17th). It is a thick refrozen crust with weak faceted snow above and below — easily visible in a snow pit. This is an unusual and unpredictable weak layer, so a wide safety margin is necessary. Slides could break wider than expected, and are most likely to be triggered from shallow trigger points like rocks or small trees. You could ride the same slope numerous times until that right spot produces a big slide.

Observations in all zones throughout December have found moderate strength and easy propagation on failures within the “Big Warmup” layer. We know it to exist at all elevations above 1000ft — even up to the highest summits. We expect this layer (and other midpack crust-facet layers) to be an ongoing issue going forward.

Depth Hoar at the Ground:

October snow followed by long cold snaps created depth hoar at the ground in most areas. These angular snow grains are well developed into a weak layer that behaves like brittle glass. As the snow gets deeper, the load over this layer increases, and it could collapse. The possibility of an avalanche stepping down to the ground will remain possible for several weeks at least.  We still have a high-consequence early-season snowpack that deserves respect and should drive conservative decision making. Any slides that break to the ground are likely to be deadly.

Snowpit profile from wind loaded area on Nadahini on 12/4: