Avalanche Forecast

The recent storm buried a mix of sun crusts on southerly aspects and weak, faceted snow on northerlies. The weather stations didn't show much more than a couple inches from the recent storm. Areas closer to the crest appeared to have received more than that, and about 10" was found at Stevens and Snoqualmie Pass. On Wednesday, I found stubborn, but firm wind slabs in exposed terrain on Blewett Pass. I also found the early February facet/crust layer to be hanging in there, only 35cm down on a northeast aspect at 4,500ft. Tests indicated that propagation is still possible. On Wednesday, professional guides were able to ski cut a number of small (D1) wind slabs above 7,000ft near Washington Pass in the neighboring East North zone. These were on northwest to north aspects. 

The warm temperatures will begin to make changes to our low elevation snowpack. Something to keep in mind if headed out to recreate in the sagebrush country. Both loose wet, and persistent avalanches may become more easily triggered during the warm part of the day in these areas. 

Blewett Pass only picked up an inch of new snow. The wind formed reactive slabs much deeper than that with new and old snow. 3/13, Photo: Matt Primomo

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.