Avalanche Forecast

Issued: Jan 28th, 2018 4:46PM

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

mbender, Avalanche Canada

Northwest Coastal.

Snowfall accumulations combined with moderate to strong winds will raise avalanche danger in the coming days. There is uncertainty with forecast snowfall amounts. Avalanche danger may be higher than indicated if amounts exceed estimates on Monday.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

MONDAY: Periods of snow, accumulations 15-25cm overnight Sunday through Monday / Moderate to strong southeast wind / Alpine temperature -4 TUESDAY: Periods of snow, accumulation 15-20cm / Moderate southwest wind / Alpine temperature -3 WEDNESDAY: Flurries / Light southwest wind / Alpine temperature -2

Avalanche Summary

On Saturday a size 2 remotely (from a distance) triggered persistent slab avalanche was reported to have run on a northeast aspect in the alpine on buried layer of surface hoar.Reports from the Shames area on Thursday detailed "touchy" conditions with natural, remote and skier triggered avalanches up to Size 2 (including an involvement of a canine member of one group), between 1000-1400 m, on south to west aspects where the mid-January crust is quite prevalent. While explosive control work on easterly aspects between 1100-1330 m, produced several storm slab avalanches up to Size 1.5 which also failed on the recently buried, mid-January crust layer.

Snowpack Summary

Approximately 50cm of recent storm snow covers a widespread crust as well as surface hoar in isolated areas at mid elevations that were buried mid-January. Surface hoar is more likely to exist in sheltered areas at treeline and below with crust elsewhere. This interface has produced easy, sudden results in recent snowpack tests in the Shames area and also recent avalanche activity at upper treeline and alpine elevations.Professionals have also been monitoring a few mid-pack layers within the snowpack including a crust/ surface hoar layer that was buried early-January and now lies 60-100 cm below the surface, and a similar layer buried mid-December that now lies 80-120 cm below the surface. Both of these layers have been reactive in recent snowpack tests producing moderate to hard, sudden results and have also produced recent large, natural avalanches in northern parts of the region near Bear Pass.The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.

Problems

Storm Slabs

New snow combined with moderate to strong winds have created slabs on top of potential weak sliding layers

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Buried weak layers in the snowpack have produced recent large avalanches in steep, unsupported terrain features.

Avoid shallow, or thick to thin snowpack areas where triggering a deeper layer is more likely.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Jan 29th, 2018 2:00PM