Avalanche Forecast

Mostly cloudy skies, cold temperatures, light winds, and minimal new snow will create a generally safe and stable snowpack on Thursday at Snoqualmie Pass. If you’re going to find an isolated pocket of unstable snow, it’s probably on a shaded slope higher in the terrain were recent wind could drift lingering soft snow. A weak storm the past few days only dropped a few inches of snow at mid and upper elevations. This wasn’t enough to create any meaningful new avalanche risk. The bigger recent story was the winds. Upper elevations experienced sustained moderate to strong winds for nearly 24hrs Tuesday into Wednesday. 

Over the past week, the snowpack around the Pass has become very aspect dependent. Shaded slopes continue to hold cold dry soft snow at mid and upper elevations. Recent windy conditions may have redistributed some of this snow into deeper pockets and scouring other surfaces. On sunny slopes, a very firm and thick surface crust formed during recent warm clear weather. Expect variable travel conditions including firm icy surfaces.

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