Avalanche Forecast

Scattered flurries will lead us into the big storm arriving Saturday night.

FRIDAY NIGHT: Cloudy with isolated flurries and up to 5 cm of snow, moderate west wind, treeline temperatures around -8 C.

SATURDAY: Cloudy with scattered flurries and 5-10 cm of snow, moderate west wind with strong gusts, treeline temperatures around -6 C.

SUNDAY: Snow throughout the day with 15-25 cm of snow, strong southwest wind, freezing level climbing to 1200 m with treeline temperatures reaching -2 C.

MONDAY: Another 20-30 cm of snow, strong to extreme southwest wind, treeline temperatures drop to -5 C.

New wind slabs were reactive on Friday, with reports of size 1 human triggered avalanches on smaller slopes and size 2 natural and explosive triggered avalanches on bigger slopes. Between Tuesday and Thursday there were several small (size 1-1.5) human-triggered wind slab avalanches, as well as some dry loose and wet loose avalanches in steep terrain.

There was some notable avalanche activity towards the end of last week and last weekend, as a bout of strong northerly winds formed large wind slabs in unusual places (eg. south, southeast, and southwest facing slopes). This created a tricky problem that resulted in a string of serious avalanche accidents. On Feb 11 two skiers were caught in a natural wind slab avalanche in a couloir on Mamquam Mountain, resulting in serious injuries. On Feb 12, a fatal avalanche was triggered by skiers at 2200 m on a west-facing slope on Phalanx Mountain (a size 2.5 wind slab). On Feb 12, another fatal avalanche was triggered by skiers at 1700 m on a treed southwest-facing slope in the Brandywine valley (a size 1 wind slab). See the incident reports here and here for details. These wind slabs have decreased in reactivity over the past the week, however may still present as a problem with the stress of new snow and wind.

As of Friday afternoon there is 10-20 cm of new snow above a widespread interface that may become a reactive failure layer for storm and wind slab avalanches over the weekend. This interface consists of a surface hoar layer at treeline, a crust below 1800 m, sun crusts on steep south slopes, and faceted surfaces and hard wind slabs in the alpine. Below the evolving surface, 80-120 cm sits on a lingering persistent weak layer from late January that consists of facets at upper elevations and surface hoar in sheltered areas. Although this structure is suspect, we have no recent reports of avalanches failing at this interface within the region.

• Back off steep and aggressive lines, stick to simple terrain.
• Use ridges or ribs to avoid areas of wind loaded snow.
• Minimize exposure during periods of heavy loading from new snow and wind.
• Recent new snow may be hiding windslabs that were easily visible before the snow fell.