Avalanche Forecast

Archived

Apr 18th, 2021–Apr 19th, 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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

North Columbia.

The best and safest riding will be high north-facing terrain that is free from cornices overhead. Expect avalanche activity on sun-exposed slopes.

Confidence

High -

Weather Forecast

A high pressure system brings clear skies and a diurnal melt-freeze cycle.

SUNDAY NIGHT: Clearing skies, 30-40 km/h northeast wind, freezing level drops to valley bottom with treeline temperatures dropping to -6 C.

MONDAY: Mostly sunny, light northeast wind, freezing level climbs to 1900 m with treeline temperatures reaching -1 C.

TUESDAY: Sunny, light wind, freezing level climbs to 2100 m with treeline temperatures reaching +1 C.

WEDNESDAY: Sunny with some afternoon clouds, light west wind, freezing level climbs to 2400 m with treeline temperatures around +4 C.

Avalanche Summary

Reports are relatively limited but there has been evidence of widespread size 1-2 wet loose avalanches on sun-exposed slopes since the warm weather arrived last week. There have also been a few large (size 2.5-3.5) wet slab avalanches reported in Glacier National Park (on Thursday, Friday and Saturday). A few recent natural cornice failures of size 2.5 did not trigger slabs on slopes below. Several glide cracks opened up and glide snow avalanches released with the warm temperatures. Glide slabs are hard to predict and can release at any time, so it is important to avoid slopes with glide cracks.

With relatively cooler temperatures on Monday the likelihood of wet avalanches will be reduced, but they will still be possible on sun-exposed slopes.

Snowpack Summary

The snow surface consists of a melt-freeze crust on solar aspects and shaded aspects into the lower alpine, which transitions into moist/wet snow during the day. Dry snow might still be found on northerly aspects in the alpine above 2200 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

Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
Avoid lingering or regrouping in runout zones.

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.