Sea to Sky Avalanche Forecast

Issued: Feb 13th, 2021 4:00PM

Sun Feb 14th Current Conditions
Alpine Considerable Treeline Moderate Below Treeline Low
Mon Feb 15th 2 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Low
Tue Feb 16th 3 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Low

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Our avalanche summary is stacking up with avalanche involvements and conditions are not expected to improve. New snow will add to (and possibly obscure) existing problems as shifting winds make slab distribution even more complex. Seek out sheltered, low consequence terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Saturday night: Mainly cloudy. Light variable winds shifting southwest and increasing.

Sunday: Cloudy with scattered flurries bringing about 5 cm of new snow, continuing overnight. Light south or southwest winds becoming strong southwest in the alpine. Alpine high temperatures around -8.

Monday: Cloudy with easing flurries from the overnight period leaving us with up to another 5 cm of new snow with new snow totals of 5-15 cm. Light variable winds. Alpine high temperatures around -7.

Tuesday: Cloudy with scattered flurries continuing from the overnight period bringing about 5 cm of new snow. Light to moderate southwest winds, potentially strong in the alpine. Alpine high temperatures around -7.

Avalanche Summary

We have preliminary information about another avalanche involvement in the Brandywine Mountain area on Saturday. We will update this summary once we have more details.

On Friday, a very large (size 3), fatal avalanche was triggered by skiers at 2200 metres on a west-facing slope on Phalanx Mountain. The avalanche is described as a wind slab that formed to the lee of recent strong east winds. Three people were involved in the avalanche and one person was killed. A second, smaller (size 1.5) wind slab was triggered by skiers on a nearby slope, again causing injury to the person involved.

A bout of strong northerly winds on Thursday caused conditions in the region to change rapidly, with new and touchy wind slabs forming in unusual places. Numerous natural releases from size 1 to size 2 were observed in the Whistler area above about 1900 metres. 

Two more skiers were involved in an avalanche in the Supercouloir feature of Mamquam Mountain on Thursday. This avalanche was a natural wind slab release ands again resulted in serious injuries and an urgent evacuation by helicopter.

Snowpack Summary

Light forecast snow amounts will feed into existing wind slab problems brought on by powerful east and northeast winds that have been redistributing loose snow into reactive wind slabs. Winds are forecast to shift again to the southwest, expanding problems to all aspects.

Forecast snow will otherwise add to around 15 cm of older low density snow (think weak, faceted snow) in shaded, sheltered areas and more widespread wind-affected snow (also progressively faceting in recent days). On solar aspects, a thin recent sun crust may be found on or right near the surface or beneath recently wind transported snow, potentially contributing to the reactivity of slabs recently formed on sun-exposed aspects.

Below the evolving surface, 50-100 cm of settled storm snow sits on a persistent weak layer from late January that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1900 m, and a sun crust on south-facing slopes. There could be more than 100 cm on this layer in wind loaded areas. Although this structure is suspect, we have no recent reports of avalanches failing at this interface within the region.

A crust from early December, currently considered dormant, may be found around 200+ cm deep in the snowpack.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of highly variable recent wind loading patterns.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2.5

A bit of new snow and shifting winds will feed into existing wind slab problems formed in response to recent outflow winds. Especially new but also recent slabs are likely to be sensitive to human triggering on Sunday. This is an all aspects avalanche problem.

Recent faceting and loss of cohesion in cornices can make them brittle and prone to fail. Give them a wide berth from above and below.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Feb 14th, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.