Archived

Avalanche Forecast

Mar 13th, 2019–Mar 14th, 2019

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

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.

Avalanche Problems

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

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