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Avalanche Forecast

Archived

Mar 17th, 2020–Mar 18th, 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.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

Little change is expected due to a stable weather pattern. Be extra cautious as slopes warm up throughout the day.

Confidence

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

Weather Forecast

A high pressure system brings clear dry conditions for the week.

TUESDAY NIGHT: Clear skies, light northeast wind, freezing level drops to valley bottom, alpine temperatures drop to -10 C.

WEDNESDAY: Clear skies, light north wind, freezing level climbing to 1500 m, alpine high temperatures around -3 C.

THURSDAY: Sunny with a few clouds, light south wind, freezing level climbing to 1700 m, alpine high temperatures around -2 C.

FRIDAY: Sunny, light southwest wind, freezing level climbing to 1900 m, alpine high temperatures around -1 C.

Avalanche Summary

On Monday warm sunny weather resulted in several wet loose avalanches on south-facing slopes in steep rocky terrain around Duffey Lakes. One natural size 2 slab was observed on a northeast alpine feature in the northern part of the region. Some large glide slab releases were reported around the Coquihalla.

Over the weekend a few small (size 1) wind slab avalanches were triggered by riders in northern parts of the region.

Looking forward, daily warming will likely cause more wet loose avalanches and potentially weaken cornices and lingering wind slabs. In northern parts of the region, the warming trend has potential for the deep persistent slab problem to reawaken.

Snowpack Summary

Surface conditions are highly variable with a mix of crusts, moist snow, and hard wind slabs. The surface will become moist on sun-exposed slopes and at lower elevations throughout the day.

In the northern part of the region (i.e. Duffey/Hurley/Gold Bridge), a deep instability may linger at the base of the snowpack. It has not produced an avalanche since Feb 17. If one were to trigger the layer, it would likely be in a thin, shallow, rocky spot. A cornice fall could also trigger it.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.