Avalanche Forecast

Issued: Mar 4th, 2019 5:01PM

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

cgarritty, Avalanche Canada

North Columbia.

Wind slabs and persistent slabs are becoming less likely to trigger, but conditions still demand assessment of suspect features in wind affected areas and around sheltered openings at lower elevations.

Summary

Confidence

Moderate -

Weather Forecast

Monday night: Mainly clear. Light east winds. Tuesday: Mainly sunny. Light east winds. Alpine high temperatures around -11.Wednesday: A mix of sun and cloud. Light east winds. Alpine high temperatures around -8.Thursday: Cloudy with scattered flurries bringing around 5 cm of new snow, continuing overnight. Light southwest winds. Alpine high temperatures around -10.

Avalanche Summary

Reports from the past couple of days show a continuation of wind slabs reacting to ski cuts, with a trend toward smaller (size 1) releases. Small (size 1-1.5) loose dry avalanches have also been observed releasing naturally from steeper, sun exposed slopes in recent days.On Wednesday, numerous rider triggered wind slab avalanches up to size 2 were reported primarily on northerly aspects at treeline and above. The largest one was a buried, hard wind slab that was sitting on facets on top of a crust. Reports of human triggered persistent slab avalanches on our January weak layers have recently been on the decline, suggesting these layers have evolved into a lower likelihood avalanche problem, but one that still requires a measure of discipline to manage effectively.

Snowpack Summary

Weeks of mainly dry, windy, and cold weather have transformed the snowpack at upper elevations into a mix of wind-affected surfaces and wind slabs of varying ages on all aspects. These wind slabs have shown prolonged reactivity because of the faceted (weak, sugary snow) they overlie. There are a couple of prominent weak layers in the upper snowpack that were buried in mid and late January. These can be found approximately 40-80 cm deep. Both layers consist of surface hoar (weak, feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most reactive at lower elevations, and especially below treeline.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.

Problems

Wind Slabs

Recently formed wind slabs can be found on all aspects, but especially to the lee of recent northeast winds. Wind slabs have recently shown prolonged reactivity due to the weak, faceted snow they sit above.

Exercise increased caution around wind loaded pockets near ridge crests and roll-overs.Steep and rocky terrain are likely places to trigger buried wind slabs.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Persistent Slabs

Two persistent weak layers are buried approximately 40 cm and 75 cm below the surface. These layers have evolved into a lower likelihood avalanche problem that still demands slope assessment and diligent group management at lower elevations.

Exercise increased caution around low elevation cut-blocks where this layer has been well preserved.Maintain diligent group management around open and/or sparsely treed slopes at treeline and below.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely

Expected Size

1 - 2

Valid until: Mar 5th, 2019 2:00PM