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Avalanche Forecast

Archived

Feb 11th, 2022–Feb 12th, 2022

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

Regions

North Rockies.

A widespread rain crust on the snow surface will make for generally safe avalanche conditions, but unwelcoming riding conditions. 

Wind slabs may exist in the high alpine where the snowpack might remain dry.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

A ridge of high pressure continues to bring dry conditions into Saturday. 

Friday Overnight: Mainly clear. Freezing level dropping to valley bottom. Moderate to strong northwest winds at ridgetop. 

Saturday: Mainly cloudy. Freezing level rising to 1900 m in the afternoon. Moderate to strong northwest winds at ridgetop.

Sunday: Cloud cover increasing. Freezing level rising to 1500m. Light to moderate westerly winds at ridgetop.

Monday: Snowing. Freezing level rising to 1000 m in the afternoon. Light to moderate westerly winds at ridgetop.

Avalanche Summary

Numerous wet loose avalanches were observed on all aspects and elevations on Thursday from the rain event that occurred on Wednesday.

Last Sunday, a deep persistent slab avalanche was likely triggered naturally by intense warming and sun and released on depth hoar or the November crust. It occurred just south of the region (see this MIN report). 

Snowpack Summary

A 1-5 cm breakable rain crust exists on all aspects and elevations from the rain event on Wednesday. Dry snow may exist in the alpine above 2300m, and will have been transported by westerly winds into wind slabs in lee areas.

Below the crust, last week's 30-50 cm of storm snow buried a weak layer of surface hoar crystals. The last reported avalanche on this layer was on February 7th in the southeast of the region and it is becoming increasingly hard to find in the snowpack with no recent reactivity in tests.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.
  • Watch for areas of hard wind slab on alpine features.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow 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.

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.