Avalanche Forecast

Issued: Apr 23rd, 2018 4:08PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Loose Wet and Cornices.

Avalanche Canada cgarritty, Avalanche Canada

Surface instabilities and cornice hazards should be firmly on your radar as you travel. Expect stability to deteriorate over the course of each day.This is our final regular forecast of the season and will expire on April 25.

Summary

Confidence

Moderate -

Weather Forecast

Tuesday: Mainly sunny. Light south winds, increasing to strong at ridgetop. Freezing level to 3000 metres with alpine high temperatures around +4. Weak overnight cooling.Wednesday: Sunny. Light west winds. Freezing level rising to 3500 metres by late afternoon and staying steady overnight. Alpine high temperatures around +6.Thursday: Sunny. Light south winds. Freezing level to 3300 metres with alpine high temperatures around +8.

Avalanche Summary

Several smaller (size 1.5) natural wind slab avalanches were observed in the region on Saturday. These occurred primarily on northwest aspects above 2400 metres.Reports from Thursday were limited to a couple of size 2 storm and wind slabs, 30 and 50 cm deep, respectively. The storm slab released naturally while the wind slab was ski cut from a steeper north aspect in the alpine.Tuesday's reports included observations of numerous natural wind slab release from size 1-2 on north through east aspects in the alpine. A skier triggered size 2 storm slab resulted in a near miss. Another recent very large (size 3.5) storm slab was also observed to have released on a large, wind-loaded alpine feature. Observations from just over a week ago also showed a pattern of heightened cornice failure activity. Looking forward, a period of increasing warming, full sun, and warm overnight temperatures will be maintaining elevated chances of cornice and loose wet avalanche activity.

Snowpack Summary

A surface crust is likely to exist on all but north aspects in the alpine and is expected to undergo melt-freeze cycles with daily warming and overnight cooling. Below the surface, about 50-70 cm of settled storm snow from the past couple of weeks overlies a supportive crust that exists on all but north aspects above about 2200 metres.This layer as well as the deeper (down about 90-120 cm) mid-March crust are of limited concern concern after warm temperatures have promoted settlement and bonding in the upper snowpack. Any remaining uncertainty with regard to their strength is generally limited to high north aspects as well as the possibility for triggering with a heavier load, such as a cornice collapse.Deeper persistent weak layers from December and January are generally considered dormant at this time but may be reactive to very large triggers. Cornice collapses become increasingly likely during periods of intense daytime warming.

Problems

Loose Wet

An icon showing Loose Wet
Daytime warming and sun exposure will promote natural loose wet avalanche activity this week - especially around steep sun-exposed terrain.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Cornices

An icon showing Cornices
Weak overnight cooling, warm daytime temperatures and strong sun will be increasing the chance of cornice failures in coming days. Cornice falls may have potential to trigger a weakness at the base of the snowpack and cause a very large avalanche.
Give cornices a wide berth when traveling on or below ridges.Cornices weaken with sun and daytime heating. Minimize your exposure to large cornices overhead.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Valid until: Apr 24th, 2018 2:00PM

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