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Avalanche Forecast

Archived

Feb 13th, 2020–Feb 14th, 2020

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

Regions

Purcells.

Although avalanche conditions are improving there is still potential to trigger avalanches on wind loaded slopes and large steep terrain features.

Confidence

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

Weather Forecast

THURSDAY NIGHT: Light flurries with 5-10 cm of low density snow, moderate wind from the west, alpine temperatures drop to -10 C.

FRIDAY: Mainly cloudy with isolated flurries and up to 5 cm of snow, moderate wind from the west, alpine high temperatures around -6 C.

SATURDAY: Mainly cloudy with sunny breaks and isolated flurries, light wind from the southwest, alpine high temperatures around -6 C.

SUNDAY: 5-10 cm of snow overnight then clearing in the afternoon, light wind from the west, alpine high temperatures around -6 C.

Avalanche Summary

A few small (size 1) wind slabs have been human triggered at treeline and alpine elevations over the past few days.

On Monday there were reports from the central part of the region of two explosives triggered deep persistent avalanches size 2.5 and 3 running on north aspects in the alpine. One of these ran on facets sitting glacial ice.  

Snowpack Summary

20-50 cm of low density snow has fallen over the past week. This snow has shown some reactivity at higher elevations where it has been redistributed it into isolated wind slabs. This snow sits above a rain crust that extends up to 1800-2000 m. 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

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Conditions may have improved, but be mindful that deep instabilities are still present.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.