Avalanche Forecast
Issued: Feb 19th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Storm slabs are expected to remain reactive to human triggering, especially in wind-loaded terrain.
Forecast will be updated at 6:30AM (PST) if overnight snowfall exceeds forecast.
Summary
Confidence
Weather Forecast
Precipitation will taper on Sunday. Following a familiar pattern, arctic air reinvades the province bringing cold temperatures and clear skies by Monday.
Saturday Overnight: Continued snowfall, 2-15 cm accumulation. Freezing level dropping to valley bottom, alpine temperatures around -10 C. Light to moderate northwesterly winds.
Sunday: Mainly cloudy, light snowfall. Alpine temperatures around -12 C. Light northwesterly winds.
Monday: Partially cloudy, light snowfall. Alpine temperatures around -20 C. Light to moderate northeasterly winds.
Tuesday: Mainly clear. Alpine temperatures around -20 C. Light to moderate northeasterly winds.
Avalanche Summary
Human-triggered storm slab avalanches are likely on Sunday.
On Friday, numerous natural and human-triggered storm and wind slabs were reported throughout the region. Most of these avalanches were relatively small and shallow. Some of the results ran on the February 15th drought layer, while others failed on density changes within the new storm snow.
Explosive control in the past week has initiated some larger persistent slabs up to size 3. Human-triggering on this layer has tapered, but we would continue to be cautious as the snowpack adjusts to new load.
Snowpack Summary
Saturday's 15-30 cm of new snow will add to this week's snowfall with 40-100 cm now overlying the old, hard surface. This surface is comprised of facetted snow, 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.
Digging deeper in the snowpack another weak interface exists of primarily surface hoar/crust now buried up to 150 cm. This surface hoar was the dominating feature in the past few weeks and is most prominent in sheltered openings at and below treeline. Reactivity on this layer has begun to taper, but we would continue to be cautious as the snowpack adjusts to new load.
The facet/crust layer that formed in early December is now buried around 150 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.
Terrain and Travel
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Closely monitor how the new snow is bonding to the old surface.
- Use small low consequence slopes to test the bond of the new snow.
Problems
Storm Slabs
30-80 cm of recent storm snow overlies the February 15th drought layer. Storm slab reactivity can be expected to persist into Sunday, especially on leeward slopes where deeper, and stiffer slabs exist due to wind loading.
Dry-loose avalanches may be seen from steeper slopes, especially where a firm crust exists below the new snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer formed in late January may be found 50 to 120 cm deep in the snowpack. This layer consists of faceted snow, a sun crust on steep solar aspect, and most notably large surface hoar crystals in sheltered terrain.
Reactivity has begun to taper, but a significant amount of new load may cause this layer to 'wake up'.
Terrain features to be particularly cautious around include the lee side of ridges, openings in trees, cut blocks, and burns, especially on northerly aspects where the layer may not be capped by a firm crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 20th, 2022 4:00PM
