Avalanche Forecast

The North and South Columbia will receive the bulk of its precipitation on Saturday as the front slides south. Winds will be 30-40km/h with gusts to 50. 

Thursday Overnight: Snow 5-10 cm. Alpine temperatures -10 and freezing levels valley bottom. Moderate westerly winds. 

Friday: Snow amounts 5-10 cm. Freezing level rising to 1800 m. Alpine temperature near -5 with strong westerly winds. 

Saturday: Snow 15-20 cm. Freezing level rising to 1000 m and alpine temperatures near -5. Strong West wind. 

Sunday: Flurries. Freezing level valley bottom and alpine temperature near -10. Moderate Southwest wind. 

Touchy storm slabs are likely on Friday.

On Wednesday, we received numerous reports of reactive wind slab avalanches mostly up to size 1.5 and several larger ones up to 2.5 from alpine features. These wind slabs ran naturally and were easily triggered by the weight of a skier. Explosive control done also initiated some larger persistent slabs up to size 2.5. 

Last week, near-daily reports came in of human-triggered persistent slab avalanches on the January 30th weak layer, with the associated surface hoar layer taking both recreationists and professionals by surprise. Reactivity has begun to taper but this buried weak layer should not be taken lightly as it may now present a low-probability, high-consequence problem. The most reactivity on this layer has been seen between 1600-2200 m in open areas in the trees, in cut blocks and on steep convexities.

15 cm to 20 cm of recent storm snow is expected to bond poorly to the old snow surface. This old surface is comprised of near-surface faceting, surface hoar growth overlying a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline.

Below this, from 60-80 cm down exists a weak layer (surface hoar. facets, crust) that was buried at the end of January. This surface hoar has been the dominating feature in the past few weeks and remains reactive creating surprisingly large avalanches. This is most prominent in sheltered openings at treeline and below treeline.

The facet/crust layer that formed in early December is now buried around 120 to 250 cm. The last reported avalanche was on January 31 from a large explosive, and before that on January 23. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. 

• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• Surface hoar distribution is highly variable. Avoid generalizing your observations.