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Avalanche Forecast

Archived

Jan 13th, 2022–Jan 14th, 2022

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

Regions

North Rockies.

Hazard will likely depend on the extent of cooling and new crust formation Thursday overnight. Storm slabs are expected to remain touchy up high where the snow remains dry, especially in wind loaded terrain. 

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Unsettled conditions are expected for Friday with a ridge of high pressure to the south and a weak storm system approaching from the west. 

Thursday night: Partly cloudy, moderate SW wind becoming strong by early morning, freezing levels may linger at around 2000-2500 m with a temperature inversion and below freezing temperatures in the valleys. 

Friday: Mainly cloudy with periods of light flurries, strong SW wind, freezing levels around 1500 m. 

Friday night and Saturday: Snowfall up to 25 cm, strong SW wind, freezing levels around 1500 m.

Sunday: Snowfall, moderate to strong SW wind, freezing levels around 1000 m.

Avalanche Summary

On Wednesday, skiers were triggered three size 1-1.5 storm and wind slabs between 1700 and 2000 m. These slabs were 20-50 cm thick. No new avalanches were reported on Tuesday but observations were limited. 

On Friday, the avalanche hazard is uncertain and will likely depend on the extent and thickness of a new surface crust. Where the skies are clear and the freezing levels drop substantially, a thick crust and lower hazard can be expected. Storm slabs will remain a concern at higher elevations, especially in wind loaded terrain. 

Snowpack Summary

On Thursday, freezing levels climbed into the alpine in the south of the region and to at least treeline in the north. With temperatures expected to drop on Thursday night, a widespread surface crust is expected to form. Below the new crust, 30-50 cm of recent storm snow has been settling rapidly with the mild temperatures. This snow overlies a previously wind-affected surface comprised of old hard wind slabs, sastrugi, and areas stripped back to the ground or old crusts. Snow at this interface was significantly weakened during the cold snap, which means the bond here remains in question. 

The early-December crust/facet interface can typically be found down 50-150 cm but has been dormant recently and is no longer expected to be creating an avalanche problem in the region. The base of the snowpack is composed of crusts and weak faceted grains, particularly in thin snowpack areas east of the divide. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be alert to conditions that change with elevation.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.