Avalanche Forecast

Issued: Apr 18th, 2017 4:19PM

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

mbender, Avalanche Canada

Purcells.

Expect the avalanche danger to increase as the temperature rises through the day.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

WEDNESDAY: Cloudy with sunny periods / Moderate southwest wind / Alpine temperature -1 / Freezing level 2000mTHURSDAY: Isolated flurries, accumulation 5-10cm / Light to moderate northwest wind / Alpine temperature -1 / Freezing level 2000 mFRIDAY: Cloudy with sunny periods / Light northwest wind / Alpine temperature 1 / Freezing level 2200mNOTE: 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

Numerous cornice triggered, large slab avalanches up to size 3 were reported on a variety of aspects in this region on Sunday. 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 i.e. a cornice fall or the weight of a smaller avalanche running.

Problems

Cornices

The likelihood of cornices triggering increases with intense sunshine and/or during the warmest parts of the day.

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.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

Convective flurries and moderate southwesterly winds may create small wind slabs in lee features below alpine ridgetops.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

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