Avalanche Forecast
Regions: Lizard-Flathead.
As the sun comes out today, solar input has the potential to substantially increase the reactivity of a buried persistent weak layer. This will demand conservative terrain travel and diligent decision making. Read more about this problem in our forecaster's blog here.
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
Thursday Overnight: Snowing in the evening with 5-15cm of low density new snow accumulation. Clearing overnight with temperatures dropping into the -15 to -20 C range in the alpine. Winds shifting northwest and easing into the light to moderate range.Â
Friday: Mainly clear and cold. Light to moderate northwesterly winds with alpine temperatures around -15 C. Cloud cover and winds increasing in the evening as a low pressure system crosses in from BC.
Saturday: A cloudy day with flurries and moderate to strong southwest winds. Alpine temperatures around -10 C with 5-15cm of new snow accumulation. Continued snowfall overnight, with the potential for another 5-20 cm of accumulation.Â
Sunday: Partially cloudy with light flurries, trace to 3cm accumulation. Light southwest winds and alpine temperatures around -12 C.
Avalanche Summary
On Wednesday, operators reported two large (size 2) explosive-triggered avalanches that broke 30-40 cm deep in the storm snow. There was also a report of several natural dry loose avalanche up to size 1.5 in the alpine.
On Tuesday, avalanche control with explosives produced numerous size 1-1.5 avalanches in the recent storm snow.
Snowpack Summary
40-50 cm of snow has accumulated since Monday with very little wind. This fresh snow likely remains unconsolidated, except where the wind is drifting it into denser slabs at upper elevations.Â
Below this layer, consolidated snow from the previous weekend storm sits over a substantial crust that formed in early December. This crust is likely 20 cm thick (or more) and is present across aspects below 2400m. A thin layer of weak facets (sugary snow) can found above this crust.Â
The lower snowpack consists of a mix of various early season crusts and mainly moist snow. Snowpack depths range from 55-170 cm at treeline elevations and taper quickly below 1800 m.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Watch your sluff: it may run faster and further than you expect.
- In times of uncertainty conservative terrain choices are our best defense.
Avalanche Problems
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 50-90 cm over a crust that formed in early December. As the sun comes out today, we may see substantial warming which will increase the reactivity of this layer and warrant conservative terrain selection.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1.5 - 3.5
Wind Slabs
It may be possible to trigger avalanches in the recent snow where it is getting drifted into cohesive slabs at upper elevations.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2