Strong West winds and up to 20 cm overnight may build reactive wind slabs.
The temperatures have dropped and so has the avalanche hazard. Keep in mind that persistent weak layers continue to linger, especially on high elevation slopes that remain winter-like.
10-25 cm of new snow may accumulate by Saturday afternoon. This accompanied by moderate to strong westerly wind at ridgetop may form fresh wind slabs on leeward slopes at treeline and above. Snowfall amounts vary across the region but winds will be consistent.
Springtime cornices are large and unpredictable. Give them a wide berth when travelling at ridge crest and avoid overhead exposure.
60-80 cm of recent storm snow sits above a crust at treeline and above. Large slab avalanches have failed on this crust in the past few days.
The warm-up a week ago produced some bigger avalanches that ran to the valley bottom. These failed on a December rain crust that exists a metre off the ground. An isolated avalanche event failed on this layer two days ago.
A cool and unstable weather pattern will exist through the weekend. Snowfall amounts vary widely across the region.
Friday Night: New snow 5-15 cm. Moderate to strong West winds at ridgetop and freezing levels near 1000 m.
Saturday/ Sunday: Cloudy with possible sunny periods with new snow 5-10 cm. Light to moderate ridgetop wind from the northwest. Freezing levels 1000 m and dropping to valley bottom overnight. Alpine temperatures near -10 C.
Monday: Mix of sun and cloud. Freezing level near 1000 m and alpine temperatures -15 C. Ridgetop winds light from the West.
On Thursday, two remotely (from afar) human-triggered storm slab avalanches were reported up to size 2 as well as numerous natural wind slabs and cornice failures up to size 3. During the warming, numerous wet loose avalanches were also seen up to size 1.5 mostly from steep slopes and terrain features.
Earlier this week, reports showed a wide range of avalanche activity. A natural storm/ wind slab and wet loose cycle were seen up to size 2.5. A few human-triggered avalanches up to size 2 and some larger size 3 persistent slabs that possibly failed on the late March crust. Upon further investigation, a persistent slab that was triggered by explosive control (reported Tuesday) was said to have failed on the end of March crust and stepped down to the early December rain crust that sits approx. one metre off the ground. That avalanche was a size 3.5.
A surface crust may exist on solar aspects up to the mountain top and on north-facing aspects up to 2000 m.
Over the past week, up to 50 cm of storm snow blanketed upper elevations. Light to moderate wind may have redistributed the storm snow in exposed high elevation terrain forming wind slab and large cornices.
The new snow brings up to 80 cm above the crust from late March. This crust is present on all aspects up to an elevation of 2500 m. Large avalanches have failed on this crust over the past few days.
The early-December rain crust is approximately a metre off the ground. Large slab avalanches failed on this interface last week following a rain and warming event.
These persistent weak layers are expected to become dormant after being tested by warming followed by cooling temperatures.
