Avalanche Forecast

Issued: Mar 31st, 2015 9:24AM

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

jlammers, Avalanche Canada

Northwest Coastal.

A weak surface hoar layer is creating touchy conditions in some areas. If you have field observations to share, please consider using the Mountain Information Network. Click here for more info.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Generally unsettled conditions are expected for the forecast period. Wednesday: Up to 5cm of snow / Moderate westerly winds / Freezing level at 1000m Thursday: Up to 15cm of new snow accumulating between Thursday afternoon and early Friday morning / Strong southwest winds / Freezing level at 1000m Friday: 2-5cm of snow / Moderate southwest winds / Freezing level at 1000m

Avalanche Summary

In general, observations have been limited in the last few days. That said, in the north of the region several avalanches in the size 1.5-2 range were reported to have been triggered remotely in alpine terrain. The March 25 interface was the culprit in these avalanches. Due to the persistent nature of this interface, avalanche activity on this layer may occur for some time after the stormy weather has ended.

Snowpack Summary

Up to 45cm of new snow has fallen since the weekend. During this period, ridge top winds were generally moderate to strong from the southwest. Dense storm slabs now exist at higher elevations and are expected to be reactive in lee terrain. Below about 1500m, surfaces are reported to be moist or wet.A layer of surface hoar that was buried around March 25 is now around 40-75 cm below the surface. There is some uncertainty regarding the current reactivity and distribution of this layer, although avalanche activity and whumpfs were reported prior to the weekend on northerly aspects in the alpine and at treeline, and touchy conditions are still being reported in the north of the region. I'd maintain a cautious approach to terrain selection as avalanches at this interface could be large and destructive. The mid-pack is generally well-settled and strong. At the base of the snowpack, weak facets may be found, particularly on shallow alpine slopes in the north of the region.

Problems

Persistent Slabs

A weak surface hoar layer has recently produced large remotely triggered avalanches, and is now buried by up to 75cm of snow. We're still getting a handle on the distribution of this layer. Until we do, I'd assume it's in most parts of the region.

Choose conservative lines and watch for clues of instability.>Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Storm Slabs

Recently formed storm slabs should gradually gain strength over the next few days. That said, large avalanches are still possible in in higher elevation, wind-exposed terrain.

Be alert to conditions that change with aspect and elevation.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 1st, 2015 2:00PM