Avalanche Forecast

Monday brought sunny skies battling with cool temperatures, developing Loose Wet avalanches due to solar input in some locations. On Tuesday, the sunny skies should start to be replaced by clouds, driving the likelihood for Loose Wet avalanches down toward unlikely. Although generally safe conditions should exist, the threat of avalanches will not be eliminated. You could still see new Loose Wet avalanches if there are long enough periods of sunshine to weaken the snow surface. Steep sun-exposed slopes will be most prone to these avalanches, which are capable of entraining large amounts of snow and traveling far distances as they descend. Avoid lingering above cliffs and terrain traps or on steep exposed slopes where getting swept off your feet by one of these slides could be more consequential. Look for warming snow surfaces, fresh rollerballs, or snow shedding from trees and rocks as signs that solar activity is strong enough to create Loose Wet avalanches. Additionally, freshly formed cornices may sag and collapse during periods of warming, so give these beasts some space by not traveling on or beneath them.

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