Avalanche Forecast

Archived

Apr 19th, 2022–Apr 20th, 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.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

North Columbia.

Carefully assess the wind slab hazard as you gain elevation. Limit exposure to slopes with cornices above.

Confidence

Moderate -

Weather Forecast

Tuesday night: Flurries bringing trace amounts of new snow with moderate west winds shifting to light north. Low of -7 at 1600 m.

WEDNESDAY: A mix of sun and cloud with no new snow expected. Light southeast winds and freezing levels rising to 1800 m.

THURSDAY: Mostly cloudy with flurries bringing up to 5 cm of new snow with light southeast winds. Freezing level rising to 2000 m.

Friday: A mix of sun and cloud with flurries bringing up to 5 cm of new snow with light northwest winds. Freezing level around 2100 m.

Avalanche Summary

Avalanche activity the last week has primarily been large cornice failures on north and east-facing slopes. For the most part, these have not triggered avalanches on the slopes below.

Snowpack Summary

15 to 30 cm of new snow overlies a variety of surfaces including old wind effected surfaces, facets and a crust on solar aspects. Below this a melt-freeze crust can be found on all aspects down 20 to 40 cm to 2000 m and mountain tops on solar aspects. Moist snow will likely be observed on solar aspects as the sun comes out.

Another prominent crust layer is found 30-70 cm deep.

Cornices are very large and exposure to slopes beneath them should be minimized, especially if the weather is sunny, warm, or windy. The snowpack deteriorates rapidly at lower elevations.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Closely monitor how the new snow is bonding to the crust.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Avoid sun exposed slopes, especially if snow surface is moist or wet.

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.

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.

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.