Avalanche Forecast

Issued: Apr 5th, 2017 3:12PM

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

shorton, Avalanche Canada

Northwest Coastal.

Wind slabs and cornices are a serious concern at higher elevations. Be cautious as you climb and continually reassess conditions.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Linger flurries with another 5-10 cm easing off through the day, southeast wind dropping to 25 km/h, freezing level up to 1200 m after an overnight freeze.FRIDAY: Mostly cloudy with isolated flurries, moderate southeast wind, freezing level up to 1400 m after an overnight freeze.SATURDAY: 5-10 cm of new snow, light southeast wind, freezing level around 1200 m.

Avalanche Summary

Preliminary observations from Wednesday report several natural wind slabs in steep alpine features around Bear Pass (up to size 2.5). Several avalanches were triggered by cornice falls earlier in the week, including one size 2.5 persistent slab avalanche on the February weak layer. A snowmobiler had a close call with a cornice fall on the weekend at South Douglas (click here for MIN report).

Snowpack Summary

Touchy wind slabs exist as higher elevations, as Tuesday night's storm delivered 15-20 cm of snow above 1000 m with strong to extreme winds. Extensive wind affect is expected in exposed terrain. An overnight freeze will likely form a crust at lower elevations that will deteriorate with the heat of the day. It may still be possible to trigger a large avalanche on the late February persistent weak layer. This combination of weak facets and crusts is buried 100-150 cm deep. Recent snowpack tests found moderate sudden results on the layer in the May Creek area on an east aspect around 1200 m.

Problems

Wind Slabs

Very strong winds on Tuesday night and Wednesday likely formed reactive wind slabs in the lee of exposed terrain.

Be aware of the potential for wide propagations due to the presence of hard windslabs.Use caution in lee areas. Recent wind loading has created wind slabs.Use caution on open slopes and convex rolls

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Cornices

Large cornices may become weak with daytime warming or during periods of stormy weather.

Give cornices a wide berth when travelling on or below ridges.Even small cornice falls may trigger larger avalanches.Minimize overhead exposure to cornices above.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

A weak layer from February produced several large human triggered avalanches at the end of March, and may still react in shallow areas. Heavy loads such as a small avalanche or a cornice fall are also possible triggers.

Avoid steep convexities or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Apr 6th, 2017 2:00PM