Avalanche Forecast

Sunday should bring mostly cloudy skies, cool temperatures, and a chance for light snowfall. If the cloud cover forecast does not verify, and the strong March sun makes an appearance, be heads up. Whenever the next round of prolonged solar radiation arrives, the few inches of recent snow will rapidly lose strength, and natural wet loose avalanches will likely occur on steep sun-exposed slopes.

Unreactive drifts, formed earlier in the week, can still be found near and above treeline but avalanches will be hard to trigger on Sunday. In isolated areas, you may find a poor bond where slick crusts or even buried surface hoar are found at the March 3rd interface, about 1 foot below the surface. You may be able to find older weak layers from late February 2-3 feet below the surface. There have been no avalanches on these layers since just after they were buried. If you're heading into remote areas or bigger, seldom-traveled terrain, take the time to assess the snowpack. Large cornices loom on most high ridges. Use caution to not travel on or underneath overhung cornices.

A skier triggered loose wet avalanche (D1.5) on a southeast aspect of Highlands Bowl, adjacent to Stevens Pass ski area. 3/5/2020. Photo: Willie Webster

March 5, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

 

Ridgetop wind transport near Washington Pass. 3/4/20 Photo: Josh Hirshberg

 

The beginning of March brought the first spring-like weather to the region. The days are getting longer and the sun (when it shines) has a noticeable effect on the snow. Alternating sun breaks and snowstorms is the theme of the week and the avalanche danger fluctuated just as fast as the weather. The southern zones and the east slopes have seen periods of light snowfall and significant sunshine while the northern zones and west slopes have had significant snowfall and occasional sun breaks. Above freezing temperatures were common at lower elevations throughout the region. 

Last week in review:  Temperatures were above freezing at most trailhead locations and concerns about the previous week’s buried surface hoar and weak layers were fading. Saturday temperatures plummeted as strong winds and new snow built wind slabs in most areas and drove the avalanche danger to considerable in almost every zone. Sunday’s calm weather and clearing in most areas helped stabilize wind slabs, but our attention turned to the strength of the sun and daytime warming. Lingering wind slabs and loose wet avalanches were forecast in every zone. For the remainder of the week, the avalanche problems in every zone were confined to the recent snow and each brief storm cycle had us thinking about wind slabs at upper elevations and loose wet avalanches from daytime warming and sunshine.

Spring isn’t actually here -- another round of cold temps and snow showers are on the way this weekend, but this past week’s oscillating weather is a good reminder to begin to shift our mindset. The sun is gaining strength, the days are getting longer, and we begin daylight savings this week. Even a brief period of sunshine can dramatically alter fresh, new snow. Check the mountain weather and avalanche forecasts for the most up to date info, enjoy the backcountry and let us know what you see out there!

--Peter Moore

Wet loose avalanche debris near Snow Lake. 3/5/20 Photo: Dallas Glass

Fresh cornice development from strong winds in the Stevens Pass backcountry. 3/4/20 Photo: Tom Whipple