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Avalanche Forecast

Archived

Mar 18th, 2020–Mar 19th, 2020

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

Regions

Northwest Inland.

Assess for wind slabs in steep terrain. The sun will weaken the snow and cornices as the day progresses.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy, light southeast wind, alpine temperature -6 C, freezing level 1000 m.

THURSDAY: Clear skies, light southeast wind, apine temperature -6 C, freezing level 1000 m.

FRIDAY: Clear skies, light to moderate northwest wind, alpine temperature -3 C, freezing level 1200 m.

SATURDAY: Mix of sun and cloud with isolated flurries, light to moderate north wind, alpine temperature -7 C, freezing level 900 m.

Avalanche Summary

No new avalanches were observed on Tuesday. Loose wet avalanche activity was observed on sun-exposed slopes on Monday.

Looking forward, avalanche activity may increase with daytime warming, as loose wet avalanche activity and cornice falls may occur naturally during the heat of the day. Lingering wind slabs and buried weak layers are still possible to be triggered by riders.

If you decide to travel in the backcountry, consider sharing your observations with us and fellow recreationists via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. Even just a photo of what the day looked like would be helpful.

Snowpack Summary

Wind has varied in direction, meaning that wind slabs may be found on all aspects, particularly in steep terrain adjacent to ridges.

A weak layer of surface hoar crystals buried early March may be found around 40 cm deep. This layer has been most sensitive to human triggering at treeline elevations.

An early-season layer of faceted grains and melt-freeze crust near the base of the snowpack may linger. The most suspect locations to trigger this layer would be where the snowpack is thin near rocky outcrops. A large load, such as a cornice fall, also has the potential of triggering it.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

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.