Avalanche Forecast

Moderate - Uncertainty is due to whether buried persistent weak layers become active, triggering avalanches, with the arrival of the forecast weather.

Friday: Cloudy with isolated flurries. Alpine temperatures near -6 and light wind from the west-northwest. Freezing levels at valley bottom.

Saturday: Snow 10 cm. Alpine temperatures near -10 and ridgetop wind moderate to strong from the northeast. 

Sunday: Mix of sun and cloud. Alpine temperatures falling to a low of -21 and a high of -14. Ridgetop wind light from the northeast. 

 

On Thursday, reports indicated several small features were reactive up to size 1 on the late-January buried surface hoar interface. I suspect that once the persistent slab gains more cohesion and stiffens, this problem may be more widespread. Even a small avalanche can catch you by surprise and have enough mass to push you into a terrain trap below. 

Fresh wind slabs and storm slabs may be touchy on Friday, especially where they sit above surface hoar, crust, or old surface facets. 

Up to 20 cm of recent snow fell by Thursday bringing 30-70 cm of accumulative storm snow from the past week over a variety of older snow surfaces. These old surfaces, at upper elevations (upper treeline and the alpine), include surface hoar in locations sheltered from the wind, surface facets, and stiff wind affected snow. At lower elevations (lower treeline and below treeline) 10-20 cm of snow sits above isolated pockets of surface hoar and a crust that is more predominant on solar aspects. Strong winds have stiffened the surface snow and have formed reactive wind slabs, especially in areas where they sit above the buried surface hoar. This recent MIN report is a great example of that. 

Additional snow and wind combined with cohesion may stress these potentially weak interfaces, creating the persistent slab problem. 

The mid-pack seems to be well settled. Deep persistent layers appear to have mostly gone inactive with the exception of the Bear Pass area and the far reaches south of Kitimat that have seen some sporadic avalanche activity on weak snow near the base of the snowpack and triggered by large loads such as explosives, icefalls or cornice collapses.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Watch your sluff: it may run faster and further than you expect.
• Pay attention to cornices and give them a wide berth when traveling on or below ridges.