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 the wind will be consistent.
Springtime cornices are large and unpredictable. The warming can pack a punch and lead to cornice failures. 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. Warming may consolidate the new snow into a reactive slab, producing avalanches. Large slab avalanches have failed on this crust in the past few days.
The warm-up last week produced some bigger avalanches that ran to the valley bottom. These failed on a December rain crust that exists a metre off the ground. With cooler temperatures, this may become dormant until the next big warm-up arrives.
A cool and unstable weather pattern will exist through the weekend.
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 1200 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, in response to warmer temperatures, numerous natural cornice failures and wet loose avalanches were seen up to size 2.5. A persistent slab size 3.5 was also reported from a northerly aspect near 2600 m. This avalanche was said to have failed the day prior.
On Wednesday, reports showed a wide range of avalanche activity. A natural storm/ wind slab and wet loose cycle was seen up to size 2.5. An older (occurred on April 5th) persistent slab was reported size 2.5, failed on the late March crust on a southwest aspect near 2200 m. Several human triggered size 2 slab avalanches were also reported.
Monday and Tuesday saw evidence of a widespread natural avalanche cycle up to size 3 but the average storm/ wind slabs were reported to size 2 and failed in the recent storm snow. Some larger avalanches may have failed on the end of March melt-freeze crust. Most notable was a natural size 3.5 storm slab that started at 2600 m and ran to the valley bottom.
A surface crust may exist on solar aspects up to the mountain top and on north-facing aspects up to 2300 m.
Over the past week, up to 40 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 with the last reactivity 10 days ago.
These persistent weak layers are expected to become dormant after being tested by warming followed by cooling temperatures.
