Avalanche Forecast

Issued: Feb 27th, 2015 7:46AM

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

rbuhler, Avalanche Canada

Northwest Coastal.

A moist snow surface is an indicator that the warm and sunny conditions are weakening the snowpack. Avoid steep sun exposed slopes during the afternoon.Are you a member of Avalanche Canada? Join today at avalanche.ca/membership

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure is the dominate feature for the next three days resulting in dry and sunny conditions. On Saturday, there is some model uncertainty regarding freezing levels which could reach as high as 2000m in parts of the region but will more likely be around 1500m. This warm air coupled with sunny conditions could make it feel unusually warm in the alpine for February. Temperature inversions are possible and it may be cooler in the valleys. Alpine winds on Saturday are forecast to be moderate-to-strong from the NW switching to NE. On Sunday, warm air conditions are again possible at higher elevations. Alpine winds are forecast to remain moderate-to-strong from the N-NW. On Monday, freezing levels are forecast to return to normal and be 500-800m. Strong outflow winds are expected for Monday.

Avalanche Summary

On Thursday, several size 1 skier initiated avalanches were reported. It is expected that these were thin wind slabs. Last week several full-depth avalanches up to Size 3 were observed on all but North aspects. If the region gets substantial warming and sun on Saturday, isolated events like these could once again become active. Loose sluffs from steep sun exposed slopes are also possible.

Snowpack Summary

A dusting of new snow has buried the previously variable snow surface which may have included wind-pressed surfaces or old wind slabs, a sun crust or old rain crust, surface hoar, and/or surface facets. A layer of surface hoar buried in the upper snowpack has been reported in some areas and is worth investigating before committing to any big alpine terrain. At the base of the snowpack, weak facets may be persisting.

Problems

Wind Slabs

Strong outflow winds have caused reverse loading and thin wind slab formation. Use extra caution as you transition into wind affected terrain.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Warming and solar radiation will destabilize the upper snowpack on steep sun-exposed slopes during the afternoon.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

This is a low probability problem with large consequences. A weak basal layer resulted in several full depth avalanches during the last sunny period which could be repeated this weekend. Avoid steep, sun exposed slopes during the afternoon.

Avoid steep unsupported planar slopes when the solar radiation is strong.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 5

Valid until: Feb 28th, 2015 2:00PM