Avalanche Forecast
Issued: Feb 1st, 2023 4:00PM
The alpine rating is Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeA persistent weak layer exists in certain terrain features in the alpine. Layers like this are unpredictable and hard to out-smart. This problem could be around for a while and a very cautious approach to large, connected, north-facing alpine terrain is prudent at this time.
Summary
Confidence
Moderate
Avalanche Summary
A couple of large (size 2-3) persistent slab, human-triggered avalanches have been reported within the last 7 days. Avalanches have occurred near ridgetops in north-to-northeast alpine terrain. Both avalanches have shown an impressive capability of propagating large distances. Here is a link to the most recent human-triggered size 3 avalanche.
If you are out in the backcountry please consider filling out a Mountain Information Network report.
Snowpack Summary
In alpine terrain, recent winds and warm temperatures have created a variety of wind-affected surfaces. Recently formed hard surfaces and surface crusts had new surface hoar and facets on top before being buried by small amounts of new snow earlier this week. This new layer should be monitored closely moving forward as new snow arrives.
Persistent weak layers of surface hoar and/or facets exist in north facing alpine features behind ridge lines, creating a number of recent, scary human-triggered avalanches.
Below roughly 1700 m a widespread, supportive, melt-freeze crust is present, with moist snow below.
Weather Summary
Wednesday night
Mostly cloudy. Trace amounts of new snow. Temperature -15 C overnight. North winds at 15 km/h in the alpine.
Thursday
A mix of sun and cloud. No new snow. Temperature rising to -8 C into the afternoon. A light north breeze.
FridayA mix of sun and cloud. Flurries possible. Temperature -7 C. Light, variable winds.
SaturdayA mix of sun and cloud. Flurries possible. Temperature low -13 C high -7 C. Light, variable winds.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- In times of uncertainty conservative terrain choices are our best defense.
- Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Persistent slabs have potential to pull back to lower angle terrain.
- Make observations and assess conditions continually as you travel.
Problems
Persistent Slabs
Buried weak layers have recently produced large, surprising avalanches. The most recent avalanche activity has been observed on north to northeast alpine terrain on preserved surface hoar buried 50-80cm. Keep in mind the potential for remotely triggered avalanches and how far these large avalanches can run into flatter terrain. Also keep in mind that stiff slabs can pull back into flatter terrain above them. These layers will be easier to trigger where the snowpack is thinner.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 2nd, 2023 4:00PM