Hatcher Pass

The last reported avalanches were observed or reported on 11/27-28.

See observations from this week HERE. 

Conditions have improved over the past 24 hours thanks to 3-5″ of new snow. Expect a variety of bed surfaces under the new snow to consist of old wind slabs, old firm wind crusts, and low density deteriorating wind slabs at low elevation.

It will be possible to human trigger a persistent slab on all aspects, at mid and upper elevation, on slopes steeper than 30º.  Triggering a slab at low elevation is unlikely. Natural avalanches are unlikely.

Yesterday’s 3-5 inches of new snow will not contribute to today’s avalanche problem. The new snow is low density, lacks cohesion, and was deposited without wind.  The possibility of triggering a slab up to 3 feet deep still exists in specific locations, most likely upper elevation where weak sugary facets and facet crust layers still exist but are becoming harder to find.

Snowpack depth varies from 1 foot to over 3 feet deep and is generally thicker on northerly aspects where prevailing winds have deposited snow throughout the season. Southerly aspects, where prevailing winds have scoured snow throughout the season, are generally shallower. Shallower areas will be easier to human trigger, and locations with deeper snowpacks will be harder to trigger, but result in larger and more consequential avalanches.

As small incremental storms continue to bury the deeper weaker layers in the snowpack, performing hand shears, probe pole tests, and instability tests will continue to give us valuable information about the potential for propagation. We are trending towards seeing less propagation in our pits.

The avalanche above is likely from 11/27-28 on a NE aspect at 3300′ on Frostbite. This avalanche is a good example of the complexity of persistent slabs which can be difficult to assess, predict, and manage. In this case, new snow combined with strong wind overloaded the weak layer.  The avalanche stepped down into the persistent weak layer while sympathetically triggering another avalanche.

While this avalanche problem continues to linger, stability also continues to improve.  Since the basal facets were buried in early November we have witnessed numerous avalanche cycles with the basal facets responsible as the culprit weak layer. The Thanksgiving warm up provided moisture, warmth, and rain that assisted weak sugary snow to round and increase the stability, especially below 3500 ft. Without any additional significant loading events, expect the stability to continue to strengthen slowly over time.

Avalanche behavior may be difficult to predict. Use safe travel protocols to increase your margin of safety.