Avalanche Forecast

Archived

Mar 25th, 2022–Mar 26th, 2022

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, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Wind slabs may be reactive to human triggering at upper elevations. Use caution in lee and cross-loaded terrain near ridge crests.

Confidence

High - The snowpack structure is generally well understood.

Weather Forecast

FRIDAY NIGHT: Mainly cloudy. 15 to 35 km/h southwest wind, alpine temperature -3 C. Freezing level dropping to 1000m

SATURDAY: Cloudy with light precipitation, 15-40 km/h southwest winds, alpine temperature rising to -2 C. Freezing level reaching 2000 m.

SUNDAY: Cloudy with precipitation, 5 cm of new snow accumulation at higher elevations. 20-50 km/h southwest winds, alpine temperature rising to 0 C. Freezing level reaching 2600 m.

MONDAY: Cloudy with snowfall, 5-10 cm accumulation. 15-30 km/h northwest winds, alpine temperature rising to -3 C. Freezing level reaching 2000 m.

Avalanche Summary

Widespread wet loose and wet slab avalanche activity was observed on Wednesday during the warm spell. Several large (size 2-3) cornice failures were also observed.

Several large (size 2-3) persistent slab avalanches occurred during the warm-up on Wednesday and Thursday. These slabs were 70 to 150 cm deep, on all aspects from 2100-2300 m. Looking forward, riders may still be able to trigger this layer in isolated areas.

Snowpack Summary

5 to 15 cm of recent snow may have formed small wind slabs in lee terrain features in the alpine from southwest wind. Below 2300 m and to the mountain top on solar aspects, a melt-freeze crust exists, with moist snow below.

A weak layer may be found around 50 to 100 cm deep. The layer consists of surface hoar crystals in treeline terrain on northerly aspects or weak faceted grains above a hard melt-freeze crust on sun-exposed slopes (i.e., east, south, west). It has been reactive between 1800 and 2300 m but given the recent rain, it is most likely to be triggered between 2000 and 2300 m. It should still be treated as suspect if you find it in your riding area.

The remainder of the snowpack is well-bonded.

Terrain and Travel

Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
Carefully evaluate steep lines for wind slabs.
When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.