Avalanche Forecast
Issued: Apr 17th, 2019 4:40PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
cgarritty,
Avalanche Canada
The storm is set to finish with a bout of intense southwest winds, which are expected to move much of our new snow into reactive slabs. The greatest new snow amounts - and avalanche danger - will be found at high elevations closest to the coast.
Summary
Confidence
Moderate -
Weather Forecast
Wednesday night: Increasing flurries bringing 5-10 cm of new snow, focused toward the coast. Strong to extreme southwest winds.
Thursday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate to strong southwest winds easing over the day. Alpine high temperatures around -5 with freezing levels to 1100 metres.
Friday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate west or southwest winds. Alpine high temperatures around -6 with freezing levels to 900 metres.
Saturday: A mix of sun and cloud. Light south winds. Alpine high temperatures around -2 with freezing levels to 1300 metres.
Avalanche Summary
No new avalanches have been reported in the region. However, dangerous avalanche conditions are likely to exist at higher elevations where loading from new snow and wind have been building reactive new storm slabs and wind slabs.
We received a great MIN report on Friday. It details a few avalanche occurrences including a size 3 on an east facing slope and lots of loose wet activity from steep terrain.
Snowpack Summary
Approximately 10 cm of new snow is expected to accumulate on the surface at higher elevations on Thursday night, bringing new snow totals since Tuesday to 20-40 cm. Forecast strong winds are expected to continue encouraging new slabs to form on the surface through Thursday.
The new snow has buried another wind-redistributed 5 to 20 cm of snow that fell on Saturday. This previous snow remains dry on high elevation north facing slopes, while a 5 to 10 cm melt freeze crust can be found instead on all other aspects.
The April 4th crust is now down 30 to 100 cm on high elevation north facing slopes. Surface hoar and facets were previously observed on this crust and it recently produced sudden results in snowpack tests. We have not heard of any recent activity on this interface, but there is a question of whether loading could reactivate in on high north aspects where it hasn't been capped by a crust.
Digging deeper, high north facing alpine terrain also has a layer of facets down approximately 120 cm below the surface which are thought to be dormant at this time.
At lower elevations, ongoing warm weather has been promoting isothermal snowpack conditions and melting the snowpack away.
Problems
Storm Slabs
Ongoing snowfall has been building up fresh storm slabs at higher elevations, especially in lee areas where southwest winds form thicker deposits. Slab depths are likely to increase with elevation and with proximity to the coast.
- Choose lower angled slopes away from overhead hazard while the new snow settles and stabilizes.
- Look for signs of instability. Shooting cracks and recent avalanches indicate unstable conditions.
- Avoid freshly wind loaded features. Thicker, touchier slabs are likely on north through east aspects
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 18th, 2019 2:00PM
