Archived

Avalanche Forecast

Feb 28th, 2016–Feb 29th, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

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

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

1: Low

The avalanche danger rating below treeline will be low

Regions: South Columbia.

New snow may not bond well to the older snow surface, especially in wind-loaded terrain. Choose your lines carefully and avoid exposure to terrain traps.

Confidence

High

Weather Forecast

Monday: Up to 15 cm overnight then cloudy with sunny breaks and a chance of flurries. The freezing level rises to around 1400 m during the day. Ridge winds are moderate or strong from the W-NW, easing to light during the day. Tuesday: Cloudy with periods of snow 5-10 cm. The freezing level is near 1400 m and winds are moderate to strong from the SW. Wednesday: Cloudy with flurries and sunny breaks. The freezing level rises to 1600 m and ridge winds are light.

Avalanche Summary

Numerous natural and rider triggered wind slab avalanches were reported on Saturday. These thin slabs occurred on a variety of aspects in wind-loaded terrain and were generally 15-20 cm deep. There were also reports of loose snow sluffing on steep north (dry snow) and south (wet snow) facing slopes. There was also a report of a small wind slab that initiated in steep terrain, ran off a cliff, and triggered a size 3 persistent slab on the slope below. This event occurred on a north facing alpine slope.

Snowpack Summary

25-40 cm of new storm snow sits on a crust on solar aspects and lower elevation terrain, and surface hoar on shady and sheltered slopes. Touchy new wind slabs are likely in exposed lee terrain at and above treeline. A weak layer of surface hoar and/or a sun crust buried February 21 is now 40-70cm below the surface. Where it exists, this layer may become reactive to human triggers as the overlying slab develops. The surface hoar and/or crust layer buried February 10 is now down 75-120cm. This layer was less reactive over the weekend with cooler temperatures, but remains a concern for large triggers like cornice falls or a smaller slide in motion. Cornices are large and potentially weak and should be avoided if possible.

Avalanche Problems

Storm Slabs

Fresh storm slabs are developing and overlie a crust and/or recently buried surface hoar. Triggering these fresh soft slabs is more likely in steep terrain that has been loaded by NW-SW winds.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3

Persistent Slabs

Smaller sluffs or storm slabs, cornice falls, or a rider/group of riders in the wrong spot may be enough load to trigger a crust and/or surface hoar layer that is buried an average of 80 cm deep.

Caution around convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5