Avalanche Forecast

Issued: Feb 17th, 2016 8:48AM

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

Recently formed storm slabs will continue to be reactive to human-triggering on Thursday and conservative terrain selection remain critical.Use extra caution on 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

5-10cm of snowfall is expected Wednesday overnight throughout most of the region. On Thursday, the south of the region can expect 10-20cm while the north should stay relatively dry with sunny breaks. Freezing levels are expected to be around 800m and alpine winds are forecast to be moderate from the southwest to west. A weak ridge of high pressure is expected to dry out most of the region on Friday except the far south which may see continued light snowfall. Freezing levels are forecast to reach around 1200m and alpine winds are expected to the light from the southeast. The next organized storm system is forecast to arrive Friday night and 10-20cm is currently being forecast for Saturday.

Avalanche Summary

On Tuesday, explosives triggered numerous storm slab avalanches between 1300 and 1500m. These were on all aspects and slabs were typically 15-40cm thick. Explosives also triggered numerous loose wet avalanches between 400 and 700m elevation. Several natural storm slab avalanches up to size 2.5 were also reported in the north of the region. Some of the natural activity was reported to be occurring in steep confined leeward features in the alpine and at treeline. 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. Storm slabs and wind slabs are expected to remain sensitive to human-triggering on Thursday. 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 1200m on Tuesday, wet snow below 800m, and almost no snow below 500m. 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 100-200 cm and remains a concern for commercial operations. This layer seems the most reactive in the north of the region and there were several large avalanches reported last week that were releasing on this layer.

Problems

Storm Slabs

An icon showing Storm Slabs
Recently formed storm slabs are expected to be very sensitive to human-triggering on Thursday. Wind loaded features are likely to have the most reactive slabs.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid freshly wind loaded features. >The new snow will require several days to settle and stabilize. >

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.
Dig down to find and test weak layers before committing to a big line. >Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 18th, 2016 2:00PM