Archived

Avalanche Forecast

Feb 23rd, 2018–Feb 24th, 2018

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

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

1: Low

The avalanche danger rating below treeline will be low

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

1: Low

The avalanche danger rating below treeline will be low

Regions: South Rockies.

Professionals are tip-toeing in the South Rockies due to the possibility of triggering a deeply buried weak layer. Avoid thin, rocky or sparsely treed slopes.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SATURDAY: Mix of sun and cloud, with a few flurries possible. Freezing level at valley floor. Light to moderate westerly winds.SUNDAY: Cloudy with flurries. Freezing level near 800 m. Moderate south-westerly winds.MONDAY: Mainly sunny. Freezing level near 600 m. Moderate westerly winds. More details can be found in the Mountain Weather Forecast.

Avalanche Summary

There have been no avalanches reported over the last couple of days, however observations of some very large slabs were made in the North Elk valley. These are thought to have failed within the last week. Whumpfing was reported at treeline in the North Elk valley as well.It is still possible to trigger a surprisingly large wind slab or persistent slab with the weight of a person or sled, especially from a convexity or thin snowpack area. If the sun is shining, avoid exposure to steep solar aspects where loose wet avalanche activity is possible.

Snowpack Summary

You are likely to find variable surfaces in open terrain after recent strong winds took out their fury on the upper snowpack. Fragile cornices and hard and soft wind slabs can be found on many alpine and treeline slopes. Ongoing strong winds are expected to keep building wind slabs, which overlie a spotty crust/surface hoar interface. The lower snowpack is weak with two primary concerns:1) A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) A rain crust with sugary facets buried in late-November near the bottom of the snowpack.Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread.

Avalanche Problems

Wind Slabs

Wind slabs may be found on a variety of slopes at and above treeline.

Avoid steep slopes below cornices.Be cautious as you transition into wind affected terrain.If triggered, the wind slabs may step down to deeper layers, resulting in large avalanches

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2.5

Deep Persistent Slabs

Deeply buried weak layers are most likely to be triggered from thin or variable snowpack areas; or with a large load, like a cornice fall.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5