Avalanche Forecast

Issued: Dec 8th, 2017 3:38PM

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

Avalanche Canada cgarritty, Avalanche Canada

The incoming storm is expected to deliver more snow (and greater avalanche danger) to coastal areas. Expect new snow to bond poorly with the surface.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday: Cloudy with flurries bringing 5-15 cm of new snow to higher elevations, increasing overnight. Light rain possible below 1000 metres. Greatest accumulations in coastal areas. Strong to extreme south winds. Freezing level dropping from about 1800 to 1400 metres over the day with alpine temperatures around 0 to -1.Sunday: Continuing wet flurries bringing approximately 10 cm of new snow to the high alpine. Light rain below about 1900 metres. Moderate to strong south winds. Freezing level to 2400 metres with alpine temperatures around +1.Monday: Mainly sunny. Strong south winds. Freezing level to 3200 metres with alpine temperatures of +5

Avalanche Summary

Warm alpine temperatures and sunshine initiated numerous wet loose avalanches to Size 1.5 on steep solar aspects in the alpine around the Terrace area on Friday. Natural slab avalanches icefall releases reached to Size 2.5 in the Bear Pass area. Looking forward, expect new snow accumulations to bond poorly with the crust and surface hoar that form our current snow surface. New snow loading may also begin to overload the December 4 surface hoar layer (now down about 15 cm), where it exists. Please submit your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Snowpack depths in the region remain below seasonal, with recent heavy wind effect creating variable depths of around 110 to 190 cm at treeline elevations in the Shames area. Solar and temperature crusts now exist on the majority of the the surface and surface hoar was observed developing on sheltered aspects above the valley cloud in the Bear Pass area on Thursday. Another layer of large surface hoar that was recently observed in the Shames area is now buried about 15 cm below the surface. Information on the distribution and reactivity of this layer is limited. Below it, storm snow received last week is gradually settling above a 5-10 cm thick crust (November 23) down roughly 70-100cm. Another layer of surface hoar (November 11) continues to be observed down approximately 140 cm in the Bear Pass area, showing some signs of improved bonding. The widespread crust/facet interface that was buried at the end of October can now be found 90-160 cm deep. Below it, the basal snowpack is a mix of weaker, sugary snow.

Problems

Storm Slabs

An icon showing Storm Slabs
Fresh storm slabs will begin to build as a storm pulse brings moderate snowfall with strong winds. Poor bonding is expected at the surface, so slabs will likely be very touchy. Expect thicker, more dangerous slabs in coastal areas and on lee aspects.
Use ridges or ribs to avoid pockets of wind loaded snow.Use extra caution in lee areas in the alpine and treeline. Storm snow will form touchy slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet
Light rain and and wet flurries on Saturday may cause small loose wet avalanches to occur, mainly in steep terrain and where rain or moist new snow accumulates.
Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Weak layers buried near the base of the snowpack can't be dismissed while new snow and wind load the surface. Releasing a thick storm slab or wind slab in the right location may provide enough of a trigger to step down a deep early season weakness.
If triggered, storm slabs may step down to deeper layers and result in large avalanches.Take extra caution around areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 9th, 2017 2:00PM