Avalanche Forecast

Archived

Apr 19th, 2021–Apr 20th, 2021

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 possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Columbia.

The best and safest riding will be in north-facing terrain that is free from cornices overhead. Plan your day around avoiding sun-exposed slopes.

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Warm sunny weather continues until a weak frontal system arrives on Thursday.

TUESDAY NIGHT: Clear skies, light northeast wind, freezing level drops to 1500 m with treeline temperatures dropping to -3 C.

MONDAY: Sunny, light wind, freezing level climbing to 2200 m with treeline temperatures reaching +1 C.

WEDNESDAY: Sunny with some clouds in the afternoon, light northwest wind, freezing level climbs to 2400 m with treeline temperatures reaching +3 C.

THURSDAY: Scattered flurries bring 5-15 cm of snow above 1800 m and light rain in the valleys, light northeast wind, freezing level around 1800 m with treeline temperatures around -1 C.

Avalanche Summary

Multiple days of above freezing temperatures resulted in widespread wet loose and wet slab avalanches on sun-exposed slopes between Thursday and Saturday. The wet loose avalanches were mostly size 1-2, but some of the wet slab avalanches were quite large and destructive (size 2.5-3.5). The large wet slabs were mostly on south and west facing slopes. See a photo of a recent wet slab in Glacier National Park here.

You can still expect wet loose avalanches and cornice falls on Tuesday, but they will be less widespread and destructive than they were over the weekend due to the relatively cooler temperatures.

Snowpack Summary

A surface crust will form overnight and then gradually break down with daytime warming. Dry snow may still be found in high north-facing terrain (above roughly 2300 m). There are no layers of concern in the snowpack, which has been melting and settling over the past week. Large cornices loom along many ridgelines.

Terrain and Travel

Avoid exposure to steep sun exposed slopes.
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

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.