Avalanche Forecast

Issued: Feb 18th, 2016 8:40AM

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 Friday and conservative terrain selection remain very important.

Summary

Confidence

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

Weather Forecast

Unsettled conditions are expected for Friday with periods of light snowfall and sunny breaks. The far south of the region could see 5-10cm of accumulation in the morning. Alpine winds are expected to be moderate from the southeast and freezing levels are forecast to reach around 1000m in the afternoon. Periods of light snowfall are expected on Saturday with moderate southerly winds in the alpine and freezing levels around 700m. A mix of sun and cloud is currently forecast for Sunday morning with a weak storm pulse arriving Sunday afternoon.

Avalanche Summary

On Wednesday, numerous storm slab and wind slab avalanches up to size 2 were reported from the areas north of Stewart.  This includes two skier triggered avalanches on northeast aspects at 1400 and 1700m elevations.  Explosives triggered numerous slab avalanches primarily on north through east aspects between 1400 and 1600m.  On Tuesday, a natural storm cycle up to size 2.5 was reported north of Stewart.  Explosives also triggered numerous storm and wind slab avalanches in the same area.  No new avalanches have been reported around Terrace but it appears that there haven't been any observers in the field in the last couple days. Recent storm slabs are expected to remain reactive to human triggering on Friday.  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 and all the recent avalanche activity has been failing within the storm snow. Moist snow was reported below 1200m on Wednesday, wet snow below 800m, and below threshold 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 remain sensitive to human-triggering on Friday. Wind loaded alpine features are likely to have the most reactive slabs.
The new snow will require time to settle and stabilize. >Be alert to conditions that change with elevation. >Stay off recent wind loaded areas until the slope has had a chance to 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.
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 19th, 2016 2:00PM

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