Avalanche Forecast
Sea To Sky
A few mm of rain/snow on Sunday is not expected to change the hazard. Low danger does not mean no danger. Stubborn old wind slabs, large cornices and the daily cycle of loose wet avalanches demand our respect.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Give cornices a wide berth while on or below ridges. Cornice falls may trigger large avalanches.
- Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
- Watch for wind-loaded pockets around ridgecrests and in the lee of exposed terrain features.
Avalanche Summary
On Friday two size 2 slab avalanches were reported from a north/northeast facing feature between 2100 and 2400 m on the Duffey. While this is technically in the South Coast Inland region, it is worth mentioning here as it is a bit of an anomaly that may be present in the more far flung portions of this region too. The slabs were 20 to 40 cm in depth and failed on surface hoar up to 4 mm in size.
Avalanche activity in the Sea-to-Sky region on Friday was limited to a size 1.5 natural cornice failure, and a size 3 cornice failure that was triggered by explosive control work.
Reports from Thursday included two recent natural storm slab releases in the Whistler area. One was a thin size 1.5 that released on a steep slope just below a ridge crest and the other is a more concerning size 3.5 that was seen on the Cheakamus Glacier from Whistler. We don't have details on the failure plane of this second release, but it may have run on the mid-February crust that was widely active about a week ago.
Snowpack Summary
A new crust exists on the surface on solar aspects at all elevations. High elevation Polar aspects (those facing north and east) continue to hold dry snow, this is also where new surface hoar has been spotted on the surface.
5 to 20 cm of wind distributed snow fell last week which came to rest on the mid-March crust on all but high elevation north aspects.
The mid-February weak layer is composed of soft facets, surface hoar, and/or crust. This layer is found 50 to 100 cm below the surface. This interface previously produced whumpfing, sudden results in snowpack tests, and even some remotely triggered avalanches. Much of this activity was attributed to buried surface hoar on north aspects at upper treeline elevations. This buried weak layer is a limited but lingering concern in a snowpack that is otherwise well settled and strong beneath this interface.
Variable winds in the past month have built up cornices on many ridgelines. They will become touchier as daily temperatures rise and when they are subject to the strong early spring sun on clear days.
Weather Forecast
Sunday looks a bit unsettled with isolated alpine rain showers/flurries. The weather pattern is pretty benign as we enter the work week with scattered cloud cover, seasonal freezing levels and no significant precipitation expected until possibly Wednesday.
SUNDAY: Scattered cloud cover, freezing level beginning at 600 m rising to 1600 m throughout the day, light east/northeast wind, 1 mm of precipitation possible.
MONDAY: Broken cloud cover, freezing level beginning at 900 m, rising to 1400 m throughout the day, light west wind, no significant precipitation expected.
TUESDAY: Broken cloud cover, freezing level beginning at 900 m, rising to 1400 m throughout the day, light west wind, no significant precipitation expected.
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Wind slabs still linger on north aspects at higher elevations. On sheltered slopes slabs may overlie a more reactive layer of surface hoar. South aspects are an additional daily concern as sun and warming set up loose wet avalanche conditions.