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Archived

Avalanche Forecast

Dec 12th, 2018–Dec 13th, 2018
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
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Another punchy storm will result in high avalanche danger in the Sea to Sky region on Thursday. Use caution heading into the backcountry at this time.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

WEDNESDAY NIGHT: 20-30 cm new snow is expected overnight.THURSDAY: 20-30 cm new snow with freezing levels rising to around 1400 m. Strong southwesterly winds.FRIDAY: 10-15 cm new snow. Freezing levels rising to around 1800 m. Strong southerly winds.SATURDAY: 2-4 cm new snow, brief periods of clear weather. Freezing levels around 800 m. Light southwesterly winds.

Avalanche Summary

Several natural avalanches were reported from Wednesday in the recent storm snow at around 2000 m. The typical size of the releases so far appears to be size 2. However, I expect the typical size to increase as there is significant amounts of new snow in the forecast.

Snowpack Summary

Snowfall beginning Sunday has deposited up to 80 cm in the Sea to Sky region. Strong to extreme southwesterly winds have accompanied the new snow and the weather forecast is calling for additional snowfall amounts to accumulate through the week. Buried under the new snow is a weak surface layer sitting over 20-30 cm of low density faceted snow. The new snow is not bonding well with the old surface layer, has slab-like properties, and is reacting to skier traffic.Prior to this storm, alpine snowpack depths varied around 150-200 cm, with an early November crust at bottom of the snowpack (down 100-120 cm). This crust appears to be breaking down at higher elevations and has been unreactive to snowpack tests. Snowpack depths disappear quickly with decreasing elevations (starting around 1800 m).

Avalanche Problems

Storm Slabs

Large slab avalanches are possible with significant incoming new snow and winds.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1.5 - 3