Avalanche Forecast Northwest Coastal

Date Issued: Valid Until:

Avalanche Canada jfloyer, Avalanche Canada

Avalanche Forecast

Wed Mar. 13th ยท 4:40PM

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Moderate
Storm Slabs Storm Slabs
Persistent Slabs Persistent Slabs

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Low

Alpine

Danger Ratings Moderate

Treeline

Danger Ratings Moderate

Below Treeline

Danger Ratings Moderate
Watch out for periods of intense weather - convective storms could bring locally heavy snow amounts, which will increase avalanche danger on Thursday.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

WEDNESDAY NIGHT: 10-15 cm new snow with strong southwesterly winds.THURSDAY: 5-15 cm new snow that may be quite localized but intense at times. Southwesterly winds 30-50 km/h. Freezing level around 700 m.FRIDAY: Light snow, around 5 cm. Freezing level around 800 m. Moderate southerly winds.SATURDAY: Moderate snow, around 10 cm. Freezing level around 1200 m. Strong southerly winds.

Avalanche Summary

One size 2 wind slab in the north of the region is worth noting: it was remotely triggered from 100 m away suggesting some sort of a persistent slab structure that won't heal overnight.In the south part of the region clouds limited observations but avalanche reports include numerous natural size 2 avalanches on all kinds of terrain 35 degrees or steeper, numerous remotely triggered size 2 slides. I suspect we'll learn more when the visibility improves and people see more terrain.

Snowpack Summary

Moderate amounts of new snow are expected Wednesday night and Thursday, which will add to the 40-60 cm of recent storm snow. This is likely bonding poorly to a wide variety of old snow surfaces: crusts on solar aspects, facets up high and surface hoar in sheltered locations. Not much further below this interface is a second weak layer that was buried on February 19 and comprises weak facets and surface hoar crystals. Recent avalanche activity appears to have been equally split between these two layers.The lower snowpack is generally strong.

Problems

Storm Slabs

Storm Slabs

Storm snow concern is greatest in colder areas in the north. Forecast winds focus concerns to wind loaded features.Previous weaknesses in the upper snowpack (30 - 40 cm of sugary facets) were activate during the storm; see Persistent Slabs below.

Be cautious as you transition into wind affected terrain.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5
Persistent Slabs

Persistent Slabs

A weak layer buried around 60 cm below the surface sits only a little below the recent storm snow and has recently been reactive.

Remote triggering is a concern, watch out for adjacent slopes.Storm or wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3