Archived

Avalanche Forecast

Nov 25th, 2017–Nov 26th, 2017

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

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

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: Sea To Sky.

A natural avalanche cycle is expected on Sunday as rain batters the snowpack. Conditions will be especially dangerous at higher elevations where rain falls on dry snow.

Confidence

High -

Weather Forecast

Sunday: Heavy rain (30-60mm) developing into wet flurries bringing up to 20 cm of new snow to alpine elevations. Strong to extreme southwest winds. Freezing level dropping from about 2200 to 1500 metres over the day. Alpine temperatures dropping from around +2 to -2 over the day.Monday: Mainly cloudy with scattered flurries bringing approximately 5 cm of new snow. Light southwest winds. Freezing level to about 1100 metres with alpine temperatures of -5.Tuesday: Periods of snow bringing 15-20 cm of new snow. Strong southwest winds. Freezing level to 1500 metres with alpine temperatures of -3.

Avalanche Summary

Wednesday's rain to mountain tops produced numerous, small to very large natural, loose, wet avalanches as rain drenched all elevations. In some areas these avalanches were associated with debris flows and several washouts along forestry roads and trails have been reported. Avalanche activity has since subsided with a return to cooler temperatures and lower freezing levels but will increase again as the new snow and wind build storm slabs at alpine and treeline elevations.

Snowpack Summary

Approximately 20-30 cm of new snow overlies the November 23 crust. This 5-10 cm thick crust can be found on all aspects above 1400 m and overlies a generally rain-saturated snowpack. Below treeline the snowpack consists of wet snow from top to bottom. In high alpine and glaciated terrain a layer of weak sugary crystals that was buried on November 9th exists above a crust near the base of the snowpack. This interface is now buried 150-240 cm deep.

Avalanche Problems

Storm Slabs

Rain will be a powerful trigger for storm slab avalanches on Sunday as it rapidly loads and warms the upper snowpack at higher elevations. Touchy new storm slabs may also form at higher elevations as rain transitions to snow over the day.

Avoid entering avalanche terrain and areas with overhead hazard during periods of rain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 3

Loose Wet

Warm, wet weather will destabilize surface snow and encourage loose wet avalanching on Sunday, especially in steep terrain. Even a small release can develop into a very dangerous problem as it gathers mass traveling downslope.

Use extra caution on steep slopes while surface snow is moist or wet.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 3