Avalanche Forecast

Issued: Mar 14th, 2017 4:34PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs, Persistent Slabs and Loose Wet.

rbuhler, Avalanche Canada

South Coast Inland.

On Wednesday, touchy storm slabs are expected in the high alpine. Extra caution is also required on all sun exposed slopes if the sun comes out in full force.

Summary

Confidence

Moderate -

Weather Forecast

On Wednesday, unsettled conditions are expected with snow flurries and sunny breaks both possible. Alpine wind is expected to be moderate to strong from the southwest. Freezing levels are forecast to drop to around 1000 m Tuesday night and reach around 1500 m in the afternoon. The next pulse of precipitation is expected to arrive Wednesday overnight or Thursday morning. There is currently quite a lot of model disagreement regarding amounts with 5-25 mm possible between Thursday morning and Friday morning. Alpine wind is expected to be moderate from the southwest on Thursday with freezing levels around 1000 m. Friday is currently forecast to be mainly dry with the next storm system arriving Friday overnight or Saturday morning.

Avalanche Summary

On Monday, numerous loose wet avalanches up to size 2 were observed in the Coquihalla area. In the north of the region, three natural size 1.5-3 cornice releases were observed on north and northeast aspects. Also in the north, a skier triggered a size 1 storm slab in a loaded alpine feature and a skier triggered a size 1 persistent slab on an east aspect at 1800 m which released down 40 cm on the late February surface hoar layer. On Sunday, two size 1 cornice releases were observed in the north of the region, one failed naturally and the other was skier triggered. On Wednesday, stability is generally expected to improve as temperatures drop. However, if the sun comes out, it can quickly destabilize the snowpack on sun exposed slopes. In the high alpine, the recent storm snow is expected to remain touchy, especially in wind loaded terrain.

Snowpack Summary

On Tuesday, freezing levels reached at least 2100 m. As temperatures drop on Wednesday, a new surface crust is expected to be widespread and the snowpack is expected to gain considerable strength. In the north of the region, the February weak layers are now down 80-120 cm. The layer of buried surface hoar has recently produced a few persistent slab avalanches. The crust/facet layer appears to be gaining strength but may also still be reactive in isolated areas. In the Coquihalla area, the crust/facet layer is down well over 1 m and appears to have gone dormant.

Problems

Storm Slabs

In the high alpine, recent storm snow is expected to be touchy on Wednesday, especially in wind loaded terrain. Extra caution is also needed around cornices right now.

Give cornices a wide berth when travelling on or below ridges.Avoid freshly wind loaded features.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A weak layer down around 1 metre is creating a low probability/high consequence scenario. It may still be possible to directly trigger this layer in isolated areas or a small avalanche or cornice fall could step down to it.

Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.If triggered, storm or wind slabs may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

If the sun comes out in full force, expect sluffing from steep sun exposed slopes. Cornices will also become weak with prolonged sun exposure.

Give cornices a wide berth when travelling on or below ridges.Be cautious of sluffing in steep terrain.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 15th, 2017 2:00PM