Avalanche Forecast

Issued: Feb 16th, 2016 8:29AM

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

Avalanche Canada rbuhler, Avalanche Canada

Storm slabs continue to develop at higher elevations and will be reactive to human-triggering on Wednesday. Conservative terrain choices remain critical.Use extra caution on steep south facing slopes in the afternoon if the sun is out in full force.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Another 5-15cm is expected Tuesday night before things dry out on Wednesday morning. Sunny breaks are possible on Wednesday and alpine winds are expected to be light from the east. Freezing levels are forecast to be 700-1000m. The next storm pulse is expected to arrive Wednesday evening. There is some model uncertainty regarding precipitation amounts and the region could see 5-25cm by Thursday afternoon. Freezing levels are expected to be around 700m on Thursday with light southwest winds. Light snowfall is expected to continue on Friday.

Avalanche Summary

On Monday, several natural wind slab avalanches size 1.5-2 were reported around Terrace. These were mainly on northeast aspects and the average slab thickness was 35cm. A size 1 storm slab was also skier triggered in the Terrace area on a steep convex roll. North of Stewart, a natural cornice failure triggered a size 2.5 deep persistent slab avalanche on a southeast aspect at 2500m. This occurred in steep unskiable terrain. Explosives in the same area triggered several wind slab avalanches size 1-1.5 as well as one size 2.5. These were mainly on north through east aspects between 1400 and 1600m, and slab thickness varied from 15-60cm. Storm slabs and wind slabs are expected to remain sensitive to human-triggering on Wednesday. If the sun comes out, natural avalanches are possible on steep south facing terrain features. In the far north of the region, deeply buried persistent weak layers may still be reactive to large triggers such as a cornice fall or a smaller avalanche stepping down.

Snowpack Summary

50-100cm of recent storm snow has accumulated over the past week and overlies a melt freeze crust which extends up to around 2000m elevation. This recent snow is reported to be bonding well to the crust. Moist snow was reported below 1100m on Sunday and wet snow below 800m. Recent wind has redistributed the surface snow at higher elevations forming wind slabs in leeward features. The early January surface hoar/facet layer is down 70-200 cm and remains a concern for commercial operations. This layer seems the most reactive in the north of the region and there have been several large avalanches reported in the past week releasing on this layer.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs are expected to continue to develop in steep, higher elevation terrain in response to loading from new snow and wind Tuesday overnight.  Wind loaded features are likely to have the most reactive slabs.
The new snow will require several days to settle and stabilize. >Avoid freshly wind loaded features. >Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Buried weak layers are still reactive in the snowpack, especially in the far north of region, and have the potential to produce very large avalanches. Thin spot triggering, cornice releases, and smaller avalanches all have the potential to step down.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 17th, 2016 2:00PM