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Avalanche Forecast

Archived

Apr 4th, 2021–Apr 5th, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
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 Columbia.

Minimize exposure to large looming cornices weakening in the sun on Monday. The new snow will be prone to point releases on south facing slopes and wind slabs may be found in immediate lees of exposed alpine terrain features.

Confidence

High -

Weather Forecast

Sunday night: Partly cloudy. Light northwest wind. Alpine temperature -8. Freezing level valley bottom.

Monday: Sunny. Light to moderate west wind. Alpine high temperatures around -2. Freezing level 2000 m.

Tuesday: Increasing cloud. Wind increasing to moderate to strong southwest. Alpine high temperatures around -2. Freezing level 2000 m.

Wednesday: 10-20 cm new snow. Strong southwest wind easing to light. Alpine temperature around -8. Freezing level 1500 m.

Avalanche Summary

Large (size 2-3) natural cornice failures have been reported recently, one on Sunday triggered a 30 cm deep storm slab. A size 2 skier triggered wind slab was reported in neighboring Glacier National Park on Saturday. Natural and skier triggered loose wet avalanches around size 1 have been reported in the past week.

On Tuesday, a skier triggered size 2.5 involvement was reported in neighboring Glacier National Park resulted in lost gear and minor injuries. The avalanche is suspected to have run on a buried crust in the upper snowpack.

Snowpack Summary

10-20 cm of recent snow may have seen some wind effect in immediate less of exposed alpine features. Reports indicate it is bonding well to underlying surfaces which include wind affected snow in the alpine or crust on solar aspects and below 1900 m. Below this elevation and on solar aspects the new snow dusts crusty surfaces down to 1500 m. Below 1500 m, the moist snowpack is quickly diminishing.

At alpine and treeline elevations, a widespread crust exists (except on north-facing slopes above 1800 m) buried 50-100 cm deep. Overall the snow seems to be bonding well at this interface, although there have been a few isolated avalanches running on deeper crust layers over the past few weeks.

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

Problems

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.

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.