Avalanche Forecast
Issued: Feb 7th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
cgarritty,
Avalanche Canada
Tuesday's observations confirm all those flurries and winds have indeed been scattering reactive wind slabs across alpine terrain, with some releasing naturally. Expect more of the same for Wednesday, with a continued chance of wind slab releases triggering a deeper snowpack layer to create larger, more destructive avalanches.
Summary
Confidence
Avalanche Summary
With the field team back in White Pass we received preliminary observations on Tuesday of a small scale natural wind slab avalanche cycle as a result of recent snowfall meeting with elevated winds, most recently from the west. Slab formation and releases appear to have been limited to alpine terrain thus far. No new persistent slab avalanches have been reported yet.
New surface instabilities aside, a couple of large (size 2-3) persistent slab, human-triggered and natural avalanches were reported last week. These avalanches occurred near ridgetops in north-to-northeast alpine terrain. These avalanches have shown an impressive capability to propagate across large distances. Here is a link to the most recent human-triggered size 3 avalanche.
If you are out in the backcountry please share your observations to the Mountain Information Network!
Snowpack Summary
Light new snow amounts continue to accumulate with southwest winds forming wind slabs on north and especially east aspects in the alpine.
As of Tuesday these light amounts added up to about 20-30 cm now resting on a variety of wind-affected surfaces and crusts, small surface hoar in places in the alpine, and a widespread 5-10 cm melt-freeze crust below roughly 1700 m.
A concerning persistent weak layer of surface hoar and/or facets is 50-80 cm deep and exists on north facing alpine features.
Check out this MIN from our field team to learn more.
Weather Summary
Tuesday night
Cloudy with flurries bringing 5-10 cm of new snow. Light to moderate southwest winds.
Wednesday
A mix of sun and cloud with easing flurries bringing up to 5 cm of new snow. Light to moderate southwest winds, increasing over the day. Treeline high temperatures around -8.
Thursday
Cloudy with isolated flurries and a trace of new snow. Light variable winds. Treeline high temperatures around -10.
Friday
Clear before clouding over midday. Winds ramping up to strong southwest. Treeline high temperatures around -9.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Wind slabs are most reactive during their formation.
- 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.
- In times of uncertainty conservative terrain choices are our best defense.
Problems
Wind Slabs
Ongoing flurries southwest winds have formed new wind slabs on north and especially east aspects. This process is expected to continue through Wednesday, keeping this problem fresh and reactive to triggers.
Avoid steep rocky slopes near ridge crests where these slabs might be capable of stepping down to deeper layers.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Buried weak layers have recently produced large, surprising avalanches. These layers will be easier to trigger where the snowpack is thin.
The most recent avalanche activity has been observed on north to northeast alpine terrain on preserved surface hoar buried 50-80 cm. Keep in mind the potential for remotely triggered avalanches and that large avalanches can run far into flatter terrain. Stiff slabs can also pull back into flatter terrain above them.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 8th, 2023 4:00PM
