Archived

Avalanche Forecast

Apr 20th, 2015–Apr 21st, 2015

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

4: High

The avalanche danger rating at treeline will be high

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

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: Glacier.

We're in a typical spring pattern with some overnight crust recovery and high daytime temperatures. Watch for the rapid deterioration of the upper snowpack on solar aspects. Plan to stay off of these slopes by mid to late morning.

Weather Forecast

Another clear sunny day is upon us with few clouds and little wind. Freezing levels are steadily rising to 2700m and expected to reach 3000m tomorrow with no overnight refreeze tonight. High pressure ridge is slowly breaking down and by Wednesday we'll have some cloud cover and light rain at most elevations into Thursday.

Snowpack Summary

Overnight refreeze created a surface crust over moist or wet snow. The snowpack on solar aspects is mostly moist and composed of multiple crusts. This will differ on sheltered north aspects in the alpine where dry snow can still be found above 1900m. Weak layers still exist in the upper snowpack on crusts or surface hoar on north aspects higher up.

Avalanche Summary

Yesterday, natural slab avalanche on Mt Fidelity peak, size 2.5, south aspect, 2500m, down ~30cm, ~200m wide, ~150m long. Similar avalanche on Bruins Ridge, 2 days ago, size 2.5, E aspect, 100m wide, 30cm deep, 250m long which ran into Hospital Bowl. Several solar avalanches to size 2.5 and one size 3 glide crack release in the highway corridor .

Confidence

Avalanche Problems

Persistent Slabs

Weak layers are down 30-60cm mostly on crusts on solar aspects. Daytime warming, loose avalanches and skiers can trigger this layer. Natural avalanches have been observed on these layers in the last 2 days.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3

Loose Wet

Strong solar radiation will have an effect on the sunny aspects today. Loose avalanches can get surprisingly large once they get going. A good plan is to stay off of large slopes that are in sun by later this morning.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Cornices

Large cornices have the potential to fall with the addition of sun and warming. Remember that cornices above shaded slopes are still very much a threat as they take in the heat on the ridge.

Cornices become weak with daytime heating, so travel early on exposed slopes.

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 3