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Avalanche Forecast

Archived

Feb 7th, 2020–Feb 8th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Moderate to strong southwest wind overnight will form wind slabs in lee terrain features at treeline and in the alpine. Fresh wind slabs will be sensitive to human triggers especially when exposed to the sun. 

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday Night: Snow, accumulation 10-20 cm, moderate to strong southwest wind, alpine high -4 C, freezing level 900 m. 

Saturday: Mostly sunny, light to moderate northeast wind, alpine high -10 C, freezing level 1000 m.

Sunday: Mostly sunny, light to moderate northwest wind, alpine high -6 C, freezing level 900 m.

Monday: Mostly sunny, light to moderate northwest wind, alpine high -3 C, freezing level 1500 m.

Avalanche Summary

On Thursday a few small (size 1) slab and loose dry avalanches were reported. 

On Wednesday several small (size 1) slab avalanches were triggered by explosives and skiers. Several small (size 1) and one large (size 2) loose dry avalanche were reported in the north of the region.

On Tuesday a few small wind slab avalanches (size 1) were observed in isolated lee terrain features.

There was also a report of two size 3-3.5 naturally triggered deep persistent avalanches on a northwest aspect at 2600m. These would have run during or just after the storm on the weekend.

Snowpack Summary

The new snow will be heavily wind affected in the alpine and at treeline after tonight's storm. The fresh snow sits on variable surfaces: Extreme southwest wind leading into last weekend has scoured windward aspects, formed loaded pockets up to 150 cm deep in alpine lees and contributed to rapid cornice growth. Below 1900 m, recent snow overlies a thick crust.

Weak faceted grains and crusts near the base of the snowpack have not been an active avalanche problem recently, despite significant new snow loads. They are still on our radar, especially in inland parts of the region.

Terrain and Travel

  • Be especially cautious as you transition into wind affected terrain.
  • Brief periods of sun could quickly initiate natural avalanche activity.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.