Avalanche Forecast

Archived

Mar 31st, 2022–Apr 1st, 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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

North Rockies.

Cautious route-finding will be important at upper elevations as fresh wind slabs are possible to trigger.

Confidence

Moderate -

Weather Forecast

Friday: Mostly overcast skies with 5-10 cm of new snow. Ridgetop wind will be moderate from the West. Freezing levels will likely rise to 1500 m during the day and fall to the valley bottom overnight.

Saturday/ Sunday: Mix of sun and cloud with isolated flurries. Ridgetop wind is moderate from the southwest and freezing levels will remain 1500 m.

Avalanche Summary

On Wednesday in the Renshaw area, several natural wind slab avalanches were reported and machine-triggered slabs up to size 1.

Several small (size 1) wet loose avalanches were observed in the Kakwa on Tuesday out of steep terrain as a result of warm temperatures and strong solar radiation.

On Monday, a size 1.5 skier-triggered wind slab occurred on south aspect at treeline. This wind slab failed on a slick crust below the new snow.

Snowpack Summary

10-20 cm of new snow overlies 20 cm of denser snow that tapers rapidly with elevation. Westerly winds have formed wind slabs in the alpine and exposed treeline. A crust or moist snow can be found below the new snow on all aspects as high as 2000 m and to the mountain top on solar aspects. Below the crust, the top 10-30 cm of the snowpack is moist.

There are no deeper concerns at this time.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Wind slabs may be poorly bonded to the underlying crust.
Cornices become weak with daytime heating or solar exposure.
As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.