Archived

Avalanche Forecast

Nov 22nd, 2011–Nov 23rd, 2011

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

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

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.

This bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to forecaster@avalanche.ca.

Confidence

Poor - Track of incoming weather is uncertain on Wednesday

Weather Forecast

Wednesday: The track of the next intense Pacific frontal system is uncertain, but at this point it appears as though it may just miss the Sea-to-Sky region. If this is the case, then expect relatively calm and cold conditions with flurries bringing light amounts of snow accumulation. If the system does hit the Sea-to-Sky region, then periods of very heavy precipitation, strong southwesterly winds, and freezing levels fluctuating between 800m and 1500m, are expected.Thursday: Another intense system is expected to bring 30-40cm with associates strong southwesterly winds and freezing levels around 800m.Friday: A high pressure ridge is expected to dry things out.

Avalanche Summary

Large destructive natural avalanches, triggered by heavy loading from snow and wind, were observed this morning. I expect this natural avalanche activity will continue with additional loading from new snow and wind, and the likelihood of human triggering to remain for the forecast period.

Snowpack Summary

Newly formed surface hoar is now buried by 50-70cm of recent storm snow. Various persistent weaknesses including facets and surface hoar, with an associated crust at upper treeline elevations, can be found down 70-150cm. A deeper crust with associated facets and/or depth hoar is approximately 50cm off the ground.

Avalanche Problems

Persistent Slabs

Particularly touchy where there is an associated rain crust, which is prominent between 1800m and 2050m. Failure plane for a recent natural avalanche cycle.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 3 - 6

Wind Slabs

Near ridgecrests and terrain breaks, and in cross-loaded gullies. Recent heavy loading from wind resulted in a natural avalanche cycle.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 5

Storm Slabs

Any open slope with enough snow to smooth out ground roughness. Recent heavy snow loading created a highly unstable situation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4