Avalanche Forecast

Issued: Apr 18th, 2017 4:24PM

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

Avalanche Canada mbender, Avalanche Canada

Convective flurries and moderate southwesterly winds may create wind slabs in lee features below ridge tops.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

WEDNESDAY: Cloudy with sunny periods / Moderate south wind / Alpine temperature -3 / Freezing level 1800mTHURSDAY: Mix of sun and cloud / light west wind / Alpine temperature -3 / Freezing level 1800 mFRIDAY: Cloudy with sunny periods / Light west wind / Alpine temperature 2 / Freezing level 2300mNOTE: The convective flurries which are common during this time of year can result in widely varying snowfall amounts throughout a region. 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, such as wind slabs, can vary greatly within a region.

Avalanche Summary

Reports from Monday indicate a few loose wet avalanches running on solar aspects at tree line and a cornice fall triggering a deep persistent weakness on the slope below to size 2.5 from very steep north facing terrain in the alpine. On Sunday two size 2.5 slab avalanches were reported in this region on Sunday. One was triggered by a falling cornice and the other by a small loose wet avalanche. Falling cornices triggering large avalanches is currently our primary 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 i.e. a cornice fall or the weight of a smaller avalanche running. Cornices remain large and continue to become more overhanging.

Problems

Cornices

An icon showing 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.
Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.Cornice failures could trigger large avalanches on sugary facets near the bottom of the snowpack.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

An icon showing Wind Slabs
Convective flurries and moderate southwesterly winds may create small wind slabs in lee features below ridgetops.
Pay attention to changing conditions with elevation.Be cautious with wind loaded pockets near ridge crests and roll-overs.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 19th, 2017 2:00PM