Take a cautious approach as you investigate the aftermath of the storm. Weak surface hoar buried by the new snow could mean storm slabs remain surprisingly reactive.
Snowfall will continue to build storm slabs through Thursday night. Be cautious about narrowing your focus to more recent wind slab formations. A weak layer of surface hoar was buried by the storm and it may prolong the reactivity of new snow across a wider area.
Thursday night: Continuing flurries bringing 10-20 cm of new snow. Moderate to strong southwest winds.
Friday: Cloudy then clearing in late afternoon/evening. Light southwest winds. Treeline high temperatures around -3, cooling over the day.
Saturday: Cloudy with isolated flurries and a trace of new snow, increasing overnight. Moderate to strong southwest winds, increasing over the day and overnight. Treeline high temperatures around reaching 0C by late afternoon.
Sunday: Cloudy with lingering flurries bringing 5-10 cm of new snow, 15-25 including overnight amounts. Moderate to strong southwest winds. Treeline high temperatures around 0C.
We don't yet have observations from Thursday's storm, but it's safe to say it was an increasingly active day for avalanches as moderate snowfall and strong winds impacted the region. Looking forward to Friday, the primary concern is likely to be wind slabs perched in leeward pockets at ridgetop and around exposed terrain features. Natural avalanches will likely taper off but human triggering will remain a real concern.
Reports of weak surface hoar grains found on the snow surface in advance of the storm are another reason to take a cautious approach in your post-storm investigations on Friday. Slabs will be particularly reactive if they formed over preserved surface hoar.
Reports in the region remain limited. Be sure to post your observations to the Mountain Information Network!
By the end of Thursday's storm, the region will have picked up 25-40 cm of new snow under the influence of strong to extreme winds. The new snow mainly buried previously wind-affected surfaces, however surface hoar was obseved in the south of the region earlier this week. It may also exist in the north. Storm slab reactivity could persist in any areas our new snow buried these weak grains.
Our new snow adds to 10-40 cm of older wind-affected snow that overlies a hard rain crust. This crust may exist right at the new snow interface or even at the surface on windward slopes. Another rain crust exists near the bottom of the snowpack.
Average snow depths in the alpine are now likely closer to 120-160 cm. Snowpack depths decrease dramatically at treeline and below, and are still below threshold for avalanching in many areas. This is changing with each storm we see in the region. Early season hazards such as rocks, stumps, and creeks are a concern at these lower elevations.
