Avalanche Forecast

Issued: Jan 21st, 2019 4:12PM

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

dsaly, Avalanche Canada

South Rockies.

Watch for fresh winds slabs and avoid shallow spots and rocky terrain where triggering deeper weak layers is more likely.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Cloudy with clear breaks. Light west wind. Alpine low -12, freezing level valley bottom.TUESDAY: Cloudy with isolated flurries, trace accumulation. Moderate to strong west wind. Alpine high -10C, freezing level valley bottom.WEDNESDAY: Cloudy with scattered flurries, 5-10 cm snow. Light to moderate west wind. Alpine high -6C, freezing level 1100 m.THURSDAY: Cloudy with sun and isolated flurries, trace accumulation. Light west-northwest wind. Alpine high -6C, freezing level 1200 m.

Avalanche Summary

A size 1.5 natural wind slab avalanche was observed in steep terrain on Sunday. Skier traffic produced a few small (size 1) avalanches in the new snow on Thursday.The most recent reports of larger avalanches are from over a week ago, when warm temperatures stressed the deeper layers in the snowpack and produced a few size 2 avalanches.

Snowpack Summary

Winds have redistributed up to 20 cm recent snow into wind slabs in the alpine and treeline. This new snow buried large surface hoar crystals and/or sun crusts, which could eventually develop into a touchy problem as snow accumulates. The most suspect terrain features will be steep slopes and rolls below 2000 m (where the largest surface hoar exists) and steep south-facing slopes in the alpine (where sun crusts exist). Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks.

Problems

Wind Slabs

Recent snow fell on weak surface hoar and/or crusts and been redistributed by wind. The deepest and more reactive deposits will be in wind-loaded terrain.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be cautious on convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2

Deep Persistent Slabs

Deeply buried weak layers remain a concern. These layers are more easily triggered in areas where the snowpack is shallow, such as near ridges and rocky terrain.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid steep, rocky terrain and shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 22nd, 2019 2:00PM