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.

cgarritty, Avalanche Canada

South Columbia.

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 3100 metres with alpine high temperatures around +4. Weak overnight cooling.Wednesday: Sunny. Light northwest winds. Freezing level rising to 3500 metres by evening and staying steady overnight. Alpine high temperatures around +7.Thursday: Sunny. Light south winds. Freezing level to 3600 metres with alpine high temperatures around +9.

Avalanche Summary

Decreasing traffic in the mountains has led to limited avalanche observations over the past few days, however a large (size 2) recent cornice fall from was observed in the north of the region on Sunday. It failed to trigger any slab.A few natural storm and wind slab releases were observed on Thursday, ranging from size 1-2.5. One of these was a size 2 slab triggered by a loose wet avalanche while the 2.5 wind slab was triggered by natural ice fall on a north aspect at 2200 metres. It featured a 45 cm crown fracture.Reports from Wednesday included an observation of a natural size 2 cornice release from a north aspect in the north of the region. Numerous natural loose wet avalanches were also observed on sun-exposed aspects in the Monashees.Observations from just over a week ago 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 70-100 cm of mostly settled storm snow overlies another supportive crust existing on all but north aspects above about 2200 metres. This layer as well as the deeper (down about 80-120 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. Cornice collapses become more likely during periods of intense warming.Deeper persistent weak layers from December and January are considered dormant at this time.

Problems

Loose Wet

Daytime warming and sun exposure will promote natural loose wet avalanche activity this week - especially around steep sun-exposed terrain.

Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.Minimize exposure when the solar radiation is strong, especially if snow is moist or wet.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Cornices

Weak overnight cooling, warm daytime temperatures and strong sun will be increasing the chance of cornice failures in coming days. Large cornice falls may have potential to trigger large avalanches.

Cornices become weak with daytime heating. Minimize your overhead exposure.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

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