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Avalanche Forecast

Archived

Mar 15th, 2020–Mar 16th, 2020

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

Regions

Sea To Sky.

A rapid rise in freezing level will occur on Monday and there is uncertainty on how quickly it will warm the snowpack. It could trigger an avalanche cycle. Treat the hazard as HIGH and avoid avalanche terrain and overhead exposure if you observe natural avalanche activity.

Confidence

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

Weather Forecast

SUNDAY NIGHT: Clear skies, light northeast wind, alpine temperature -4 C.

MONDAY: Clear skies, light northeast wind, alpine temperature 1 C, freezing level 2400 m.

TUESDAY: Mix of sun and cloud, light to moderate northeast wind, alpine temperature -1 C and strong valley-bottom diurnal temperature changes, freezing level 1900 m.

WEDNESDAY: Clear skies, light northeast wind, alpine temperature -1 C and strong valley-bottom diurnal temperature changes, freezing level 1900 m.

Avalanche Summary

No new avalanches were observed on Sunday. 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.

Looking forward, loose wet avalanche activity and cornice falls could be triggered with the warming trend. The potential of triggering wind slab avalanches remains possible in steep, alpine terrain.

Snowpack Summary

An intense warming trend will raise the freezing level to around 2400 m.The warm air, coupled with strong radiation from the sun with clear skies, may rapidly weaken the snowpack and cornices. Expect to find moist or wet snow during the day, which could freeze into a melt-freeze crust overnight.

In the alpine, hard wind slabs may be found on all aspects due to variable wind directions. Recent wind has blown from the northeast, forming wind slabs in south to southwest terrain features. 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. The likelihood of triggering this layer may increase during this warming trend. There is also the potential for cornices to fail from warming, which could act as a trigger.

Terrain and Travel

  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
  • Carefully evaluate steep lines for wind slabs.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Problems

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.

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.