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Avalanche Forecast

Archived

Mar 14th, 2020–Mar 15th, 2020

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

Regions

Sea To Sky.

Strong northeast wind has formed wind slabs on atypical aspects. A warming trend will start to destabilize the snowpack on sun-exposed slopes as well as cornices.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

SATURDAY NIGHT: Clear skies, moderate northeast wind, alpine temperature -14 C.

SUNDAY: Clear skies, moderate to strong northeast wind, alpine temperature -7 C, freezing level rising to 1000 m.

MONDAY: Clear skies, light to moderate northeast wind, alpine temperature 1 C, freezing level 2300 m.

TUESDAY: Clear skies, light to moderate northeast wind, alpine temperature 0 C, freezing level 2000 m.

Avalanche Summary

A few small (size 1) wind slab avalanches were triggered naturally and by riders on Saturday. They were in alpine terrain and close to ridges.

It will remain possible for humans to trigger wind slab avalanches. Loose wet avalanche activity and cornice falls could also be triggered with the warming trend.

Snowpack Summary

A major warming trend is forecast for the coming days, which could rapidly weaken the snowpack and cornices. Wind slabs may be found on all aspects due to variable wind directions. Recent wind has blown from the northeast, forming fresh wind slabs in south to southwest terrain features at higher elevations. In sheltered terrain, about 30 cm of snow may overly a melt-freeze crust and potentially small surface hoar crystals.

Weak faceted snow and melt-freeze crusts exist near the base of the snowpack in some of the region, particularly the eastern and northern parts. This layer is considered dormant, as it hasn't produced an avalanche since February 20th. This layer may require a very large load, such as a cornice fall, or rapid weather changes to reactivate.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.