Avalanche Forecast

Archived

Mar 17th, 2020–Mar 18th, 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.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Rockies.

Wind slabs may still be found and the snowpack will weaken during the heat of the day, particularly on sun-exposed slopes. This warming is capable of triggering large avalanches.

Confidence

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

Weather Forecast

TUESDAY NIGHT: Cloudy with isolated flurries, moderate northeast wind, alpine temperature -10 C.

WEDNESDAY: Cloudy with afternoon clearing, light to moderate northwest wind, alpine temperature -4 C, freezing level 1600 m.

THURSDAY: Cloudy, light southwest wind, alpine temperature -12 C, freezing level 600 m.

FRIDAY: Clear skies, light to moderate northwest wind, alpine temperature -5 C, freezing level 1500 m.

Avalanche Summary

Many wind slab avalanches were observed in the region over the past few days caused by the reverse loading pattern. They may have been triggered from warm air temperature and sunny skies heating them up on sun-exposed slopes.

Snowpack Summary

Sunny skies have formed a melt-freeze crust on sun-exposed slopes. Recent strong easterly wind has produced wind slabs on lee terrain features. This wind direction is atypical, so you may find wind slabs in terrain features that don't usually have them.

A layer of faceted grains overly a melt-freeze crust from early February. This layer currently sits 40 to 80 cm below the surface.

The base of the snowpack contains basal facets that are most prominent in shallow, rocky start zones.

Terrain and Travel

Carefully evaluate steep lines for wind slabs.
Minimize exposure to sun-exposed slopes when the solar radiation is strong.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
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.