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Avalanche Forecast

Mar 4th, 2021–Mar 5th, 2021
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
4: High
The avalanche danger rating below treeline will be high
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Sea To Sky.

With heavy snowfall and strong winds on Friday, natural avalanches are likely. Consider your ability to recognize and avoid terrain as travel in avalanche terrain is not recommended.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

A powerful storm is impacting the region

Thursday night: Overcast, 20-30 cm of new snow, strong south wind with extreme gusts at ridgetops, freezing level dropping to 1100 m.

Friday: Overcast, 20-30 cm of new snow, strong south wind with extreme gusts at ridgetop, freezing level climbing to 1400 m in the morning and dropping to 1000 m by late afternoon. 

Saturday: Mostly cloudy, 5-10 cm of snow, light southwest wind, freezing level near 1100 m. 

Sunday: Mostly cloudy, 10-15 cm of snow, moderate south wind, freezing level near 1000 m. 

Avalanche Summary

Natural and human-triggered avalanches are likely on Friday.

There continue to be reports of both natural and explosive-triggered cornice falls (see this MIN report near Rainbow Mountain).

Snowpack Summary

As much as 30-50 cm of snow could accumulate above 1400 m by the end day on Friday. Strong south winds will contribute to rapid slab formation, making natural avalanches likely. The combination of wind and snow has the potential to weaken cornices, which can act as triggers on slopes below. 

In isolated areas with a shallower snowpack in the region, a layer of facets, spotty surface hoar, and/or crusts buried in mid-February may still be preserved. There have been no avalanches reported on this layer; however, large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow and wind have the potential to this deeper layer in areas where it may still exist.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.

Avalanche Problems

Storm Slabs

Heavy snowfall on Friday is expected to rapidly accumulate above 1300 m, forming a widespread reactive storm slab problem. Storm slabs may be more reactive in wind-drifted areas. Anticipate deteriorating conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1.5 - 2.5

Cornices

Cornices are large and looming, and they may release naturally under the current conditions. Cornice falls can act as triggers on slopes below.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1.5 - 2.5

Loose Wet

Heavy rain at lower elevations may initiate loose wet avalanches. A saturated snow surface, pinwheeling, or point releases from rocks are good indicators of this instability. 

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 1.5