Archived

Avalanche Forecast

Mar 18th, 2013–Mar 19th, 2013

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

4: High

The avalanche danger rating in the alpine will be high

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

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

Regions: Northwest Inland.

Avalanche hazard in exposed areas will increase rapidly as the wind picks up.

Confidence

Poor - Due to limited field observations

Weather Forecast

Synopsis: A Frontal system passes mostly to the south of this region on Tuesday night/Wednesday, bringing generally light precipitation.Tuesday: Flurries, with light snowfall starting late in the day. Freezing level 500 m. Southwesterly ridgetop winds increasing to around 50 km/h.Wednesday: Around 5 cm new snow. Freezing level 500 m. Winds light southeasterly.Thursday: Mostly dry with some good sunny breaks. Gusty northwesterly winds.

Avalanche Summary

On Saturday, a size 2 avalanche was triggered remotely on a south aspect at 1800 m. This avalanche ran on the new snow/crust interface. On Friday, a size 2 remote-triggered avalanche was reported from a west aspect at 1450 m, likely failing on the March 9th surface hoar layer down around 50 cm. Another human-triggered avalanche was reported on Friday from a north aspect slope.

Snowpack Summary

20-40 cm of recent storm snow rests on a variety of old snow surfaces, including crusts, previous wind slabs and surface hoar (buried March 9th). Warmer temperatures and recent winds have now set this new snow into a reactive slab. The March 9th surface hoar layer is reported to be very touchy and appears to exist at all elevations and on a variety of aspects. I suspect cornices have become well-developed and could easily become unstable with daytime heating. The mid snowpack is generally well settled and strong.

Avalanche Problems

Storm Slabs

Recent new snow has consolidated into a slab and is reacting to human triggers. The primary weak layer comprises surface hoar and appears to be touchy.

Avoid large alpine features.>Choose conservative lines and watch for clues of instability.>Avoid open slopes and convex rolls where buried surface hoar may be preserved.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 5

Cornices

Cornices are well developed. They are likely to be most sensitive when exposed to daytime heating or solar radiation.

Do not travel on slopes that are exposed to cornices overhead.>Give cornices a wide berth when travelling on ridges.>

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 6