Avalanche Forecast

Issued: Feb 16th, 2020 5:00PM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada shorton, Avalanche Canada

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With inviting sunny weather in the forecast for the next few days be mindful that triggering large deep persistent slab avalanches remains in concern on rocky alpine slopes.

Summary

Confidence

High - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

SUNDAY NIGHT: Partly cloudy, light northwest wind, alpine temperatures drop to -12 C.

MONDAY: Mix of sun and cloud, light northwest wind, alpine high temperatures around -8 C.

TUESDAY: Mostly sunny, light wind from the northwest, alpine high temperatures around -8 C.

WEDNESDAY: Sunny, light northwest wind, alpine high temperatures around -5 C.

Avalanche Summary

Reports from Sunday were limited to a few small (size 1) wind slab and dry loose avalanches, and a few small cornice falls. Large sporadic avalanches have been reported every few days over the past weeks. Most recently a size 2.5 deep persistent slab avalanche was observed in steep rocky alpine terrain on a southwest slope near Golden on Thursday (see MIN report) and a large snowmobile triggered avalanche was reported on a convex roll at treeline at Quartz Creek on Wednesday (see MIN report). These isolated large avalanches highlight the importance of careful snowpack and terrain evaluation in the Purcells.

Snowpack Summary

10-20 cm of fresh snow and a total of 30-60 cm of snow from the past two weeks sits on the surface. This snow has shown some reactivity at higher elevations where it has been redistributed it into wind slabs. Sun crusts can be found near the surface on steep south-facing slopes and a hard rain crust can be felt beneath the snow at below treeline elevations. The middle of the snowpack is generally settled but the base of the snowpack contains basal facets. It remains possible to trigger these deep weak layers in shallow rocky start zones or from a heavy trigger such as a cornice fall. 

Terrain and Travel

  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Problems

Wind Slabs

An icon showing Wind Slabs

Watch for steep or convex slopes at higher elevations where recent snow has been blown into wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Weak snow at the bottom of the snowpack continues to pose a deep persistent slab avalanche problem. Steep rocky alpine features are the most likely trigger points. Use extra caution if big alpine slopes are getting hit by the sun.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3.5

Valid until: Feb 17th, 2020 5:00PM