Avalanche Forecast
Issued: Feb 11th, 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.
trettie,
Avalanche Canada
Avoid wind loaded terrain near ridge crests where reactive wind slabs are most likely to be found. If more than 20cm of new snow is observed than storm slabs could exist at all elevations and aspects.
Summary
Confidence
Moderate
Avalanche Summary
With the field team back in White Pass we received observations on Friday of wind slabs reactive to riders and failing naturally with increasing wind from the southwest. The most notable avalanches were a size one wind slab that was remotely triggered by a sledder on a northwest aspect at treeline and the skier accidental detailed in this MIN.
As we track a persistent layer deeper in the snowpack, the most recent reports are now over a week old when a couple of large (size 2-3) persistent slab, human-triggered and natural avalanches occurred near ridgetops in north-to-northeast alpine terrain. These avalanches showed 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 with the Mountain Information Network!
Snowpack Summary
Ongoing southerly winds have redistributed up to 50cm of recent storm snow into wind slabs on northerly aspects and pressed or scoured southerly aspects. Soft snow can still be found in sheltered terrain. The above mentioned storm snow sits over a crust that extends up to 1700m.
Our field team continues to track a persistent layer of surface hoar and/or facets 50-100 cm deep, found on north and east aspects in the alpine and upper treeline. This layer has not produced any recent avalanches in the region and producing more stubborn results or non-results in snowpack tests recently.
Weather Summary
Saturday Night
Cloudy with 5 to 15cm of new snow expected. Moderate to strong southwest winds and a Low of -4 at 1500m.
Sunday
Cloudy with up to 10cm of new snow expected. Light southwest winds and a high of -4 at 1500m.
Monday
Mostly cloudy with 5cm of new snow expected. Light variable winds and a high of -8 at 1500m.
Tuesday
A mix of sun and cloud with flurries bringing a few centimeters of new snow. Moderate southwest winds and a high of -10 at 1500m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- 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.
Problems
Wind Slabs
Ongoing south and southwest winds have been building up the wind slab problem on north and east aspects.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Buried surface hoar produced large, surprising avalanches last week. This layer is on a strengthening trend, but it may still be triggerable where the snowpack is thin. Avalanche activity associated with this problem was observed on north to northeast alpine terrain on preserved surface hoar that is now buried up to 100 cm deep. Keep in mind that large avalanches can run far into flatter terrain and that 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 12th, 2023 4:00PM
