Avalanche Forecast

Snow and Avalanche Discussion

Increasing moderate winds and clouds came in Monday at the leading edge of the first significant storm system in a while. The Olympics will be largely rain-shadowed, but enough new snow will fall Monday night and Tuesday for significant wind transport of snow and wind slab development. We are going to have to start thinking about slabs again. Expect small wind slabs near and above treeline to be most reactive where they sit on weak snow surfaces. Look for them near ridgelines, particularly if they are recently scoured or freshly corniced. When in doubt, travel safely on ridges and steer clear of wind-loaded slopes greater than 35 degrees.

This storm comes in following a lengthy generally dry spell in the Hurricane Ridge area which brought a weekend with mostly sunny skies (more on Sunday than Saturday), light winds and moderating temperatures with no reported avalanche activity other than loose dry avalanches on very steep northerly aspects. These conditions likely led to the development of new weak surfaces and crusts that will lie under the Monday night / Tuesday storm snow. A second weaker layer of surface hoar was buried March 7th by 3-6” by a quick shot of snowfall. Wind slabs sitting atop either of these layers are likely to produce larger and more widely-propagating slabs that could be large enough to take you for a dangerous ride.

During the spring, steer clear of traveling on or below cornices, especially during periods of extended sun breaks.

Forecast schedule

For the 2018-19 winter season, avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays.

During the week, No Rating will be issued but forecasts will include expected conditions and relevant travel advice. While this avalanche forecast is focused on backcountry avalanche conditions expected in the Hurricane Ridge area, we want to hear about your observations from other parts of the Olympics as well.

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.