Avalanche Forecast

Wednesday will be a bit of a transition day for the snowpack around Snoqualmie Pass. The snowpack will be changing from a cold winter storm to slightly warmer temperatures, decreasing snow showers, and partly sunny skies. Expect the conditions to change quickly. Slopes you travel in the morning may be very different by mid-day.

This storm didn’t produce quite as much snow as expected around Snoqualmie Pass, but combined with significant winds we did notice a marked increase in the avalanche danger. Alpental Ski Patrol noted a few small natural storm slabs on steep slopes, mainly at the bases of cliffs.

The new snow buried a variety of snow surfaces including firm crusts, wind packed snow, facets, and surface hoar. So far we don’t have any confirmed avalanches on these layers, but they are on our mind. Take the time to look at the base of the new snow. Do you see a thin grey line? Do small slope tests fail and avalanche? If so, you may be dealing with a new buried weak layer. We’ll keep our eye on this layer over the next few days.

March 10, 2019

February started stormy and cold with very active avalanche conditions on persistent weak layers. The month finished with continued cold temperatures but drier weather allowed avalanche activity to taper off. Persistent weak layers that were buried early in the month (Feb 8th) are now unreactive, though you can still find the grains.

Aside from the series of storms in early to mid-February, most regions have measured relatively light snow accumulation in the past 3 weeks. Snow has stayed soft especially on shaded slopes and faceting and surface hoar have been plentiful. While there has been plenty of sunshine since mid-February, very cold temperatures have kept melt-freeze crust to a minimum on sunny slopes.

A natural loose wet avalanche (D1.5) on a southeast aspect of Lichtenberg Mtn at 5,400ft. 3/10/2019. Photo: Josh Hirshberg

Recent Avalanches

Our attention shifted to the upper snowpack. Recent avalanche problems have largely focussed on wind transported snow and weak snow surfaces on both dry, shaded slopes and sun-exposed aspects. In some locations, a weak layer of surface hoar and facets was buried on March 6th. We’ll keep an eye on this interface as we move into the future.

A skier-triggered storm slab avalanche (D1.5) on Shuksan Arm, north aspect, 5200ft. 03/09/19 Adam U Photo. 

Moving Forward

As we move further into March, there are two points to consider:

• The strength of the March sun: As the sun creeps higher into the sky and the days grow longer, the sun can have a greater impact on the snow surface. When the sun comes out, expect things to change quickly. You may see avalanches conditions change with natural loose avalanches originating from sunny slopes, surface snow becoming thick and heavy, and slabs taking on a moist to wet snow character.

• Weak surfaces: facets and surface hoar have blanketed snow surfaces in many zones. Any significant snowfall will bury well-developed and widespread persistent weak layers. Recently, most storms have not delivered enough precipitation to cause a problem.