Avalanche Forecast

Issued: Apr 21st, 2017 4:55PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Cornices, Wind Slabs and Loose Wet.

jsmith, Avalanche Canada

Cariboos.

Cornice failures could trigger large avalanches on sugary facets near the bottom of the snowpack.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

SATURDAY: Mostly cloudy with isolated flurries / Moderate southeast wind / Freezing level 2000mSUNDAY: Cloudy with flurries / Moderate southwest wind / Freezing level 1600mMONDAY: Cloudy with isolated flurries / Light West wind / Freezing level 1700mNOTE: Convective flurries, which are common this time of year, can result in widely varying snowfall amounts. These spring squalls routinely drop 20+ cm of snow in one valley while the adjacent drainage remains dry. For this reason, the distribution of avalanche problems associated with new snow vary greatly within a region.

Avalanche Summary

A natural cornice triggered size 2.5 persistent slab avalanche that stepped down to glacier ice was reported on Thursday. Exposure to large overhanging cornices remains a significant concern.

Snowpack Summary

Recent new snow tree line and above has been redistributed by west and south winds. Cornices remain large and continue to become more overhanging. The middle of the snowpack is generally well settled and continues to transition into a spring melt/freeze regime except for high elevation northerly aspects. Expect the entire thickness of the snowpack to be moist or wet at lower elevations. At upper elevations a deep persistent layer consisting of facets sitting on a crust that was buried back in November has been sporadically reactive to heavy loads such as a cornice fall or the weight of a smaller avalanche running.

Problems

Cornices

Minimize exposure to slopes with large cornices overhead when it is cool and cloudy and completely avoid them if it is warm and/or sunny.

Cornice falls have the potential to trigger deeply buried weak layers.Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

Lingering wind slabs may still be reactive in isolated areas below alpine ridgetops.

Pay attention to changing conditions with elevation.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Loose wet avalanches may trigger deeply buried weak layers, resulting in large avalanches.

Pinwheeling snow below cliffs is a common sign that loose wet avalanches are becoming more likely.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 22nd, 2017 2:00PM