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Archived

Avalanche Forecast

Feb 16th, 2021–Feb 17th, 2021
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
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
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

Regions: South Coast.

New snow has accumulated over a persistent weak layer and, at least initially, has not bonded well to the old surface. Give the snowpack time to heal, choose low angle terrain and avoid slopes that become sticky or moist.

Confidence

Low - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

TUESDAY NIGHT: Cloudy, clearing overnight / moderate northwest wind / ridgeline temperature low -5 / freezing level dropping below 500 m

WEDNESDAY: Mostly sunny with scattered clouds / light northerly wind / ridgeline temperature high +3 / freezing level around 1000 m

THURSDAY: Scattered clouds and incoming flurries beginning to accumulate overnight / moderate southerly wind / freezing level rising to about 1300 m in the afternoon

FRIDAY: Snow, up to 20-30 mm by morning / moderate southerly wind / ridgeline temperature high +1 / freezing level around 900 m

Avalanche Summary

Riders found soft low density storm snow rapidly gaining strength and reactivity as temperatures warmed Monday. Slab avalanches size 1-1.5 and 15-30 cm deep released naturally and were triggered by skiers and explosives in the afternoon. There are some tremendous visuals in this MIN report. 

Snowpack Summary

Warm temperatures have transitions 15-30 cm new snow from low density powder to moist snow and crusts. At upper and alpine elevations, dry snow sits on a variety of wind affected surfaces and older crusts.

Click here to check out North Shore Rescue's snowpack update from February 12. It's an excellent snapshot of conditions on the North Shore prior to the advance of the recent storm pattern.

Beneath 15-30 cm recent snow there is a rather unusual mix of facets, thin breakable crust and isolated pockets of surface hoar. There is then 30-40 cm of gradually faceting snow, and then a wide spread and supportive crust underneath. 

Terrain and Travel

  • Closely monitor how the new snow is bonding to the old surface.
  • Be alert to conditions that change with elevation.
  • Watch for unstable snow on specific terrain features, especially when the snow is moist or wet.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet

Avalanche Problems

Storm Slabs

The 15-25 cm storm snow initially did not bond well to the old weak surface, and the warmer temperatures may continue to make slabs sensitive to triggering. This problem is more likely at upper elevations where warm temperatures impact previously dry snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Loose Wet

Sun and rising temperatures may produce a moist snowpack by the afternoon.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible

Expected Size: 1 - 1.5