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Archived

Avalanche Forecast

Mar 29th, 2021–Mar 30th, 2021
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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: South Coast.

Storm slabs at higher elevations may be reactive on Tuesday, especially in wind-loaded areas. 

The spring sun packs a punch and can quickly initiate natural avalanche activity and weaken cornices. Back off slopes if you see natural avalanches, snowballing and moist snow surfaces.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

A ridge of high pressure will dominate for the next couple of days bringing cooler and dryer conditions.

Tuesday: Mix of sun and cloud. Ridgetop wind light from the northwest. Alpine temperatures near -2 and freezing levels 700 m.

Wednesday: Mix of sun and cloud. Ridgetop wind moderate from the southwest. Alpine temperatures near +7 and freezing levels 2300 m. 

Thursday: Cloudy with light precipitation amounts. Ridgetop wind moderate from the southwest. Alpine temperatures near +6 and freezing levels 2100 m. 

Avalanche Summary

On Sunday, a recent MIN report showed the new 10 cm of storm snow was easily running on a firm crust below 1200 m. The recent storm snow may start to settle and bond by Tuesday. However, wind-loaded slopes at upper elevations may take longer. Wind slabs may be reactive to human triggers. 

Solar facing slopes could destabilize rapidly when the sun is on them and initiate natural wet loose avalanches. Cornices are large and could also deteriorate under the warm spring sun. They require a large berth from above and below.

Snowpack Summary

A mix of rain and snow brought 30-50 cm/mm of precipitation to the region since the weekend, accompanied by moderate to strong southerly winds. This precipitation fell on about 30-50 cm of older snow that fell last week. The average snowpack depth at treeline elevations is 350 cm. 

A solid melt-freeze crust exists at lower elevations that previously saw rain. 

Along ridgelines, cornices are large and may weaken when the sun comes out. 

Terrain and Travel

  • Brief periods of sun could quickly initiate natural avalanche activity.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of highly variable recent wind loading patterns.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Cornices become weak with daytime heating or solar exposure.

Avalanche Problems

Storm Slabs

30-40 cm of fresh snow has formed widespread storm slabs at upper elevations. These are expected to remain reactive to human triggering on Tuesday, especially in wind loaded areas. 

With so much new snow, even brief periods of sun can trigger natural avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Cornices

Cornices are large and looming along many ridgelines, and have likely grown with the recent snow and wind. They become increasingly weak when the sun comes out.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 2 - 3