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Avalanche Forecast

Archived

Feb 20th, 2022–Feb 21st, 2022

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

Regions

North Rockies.

Northeasterly outflow winds will redistribute the storm snow into fresh wind slabs in more atypical areas, which could take riders by surprise. 

Avoid wind-loaded areas and carefully assess the bond of the new snow to the old surface.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

Bundle up in your warmest gear, arctic air is here! 

Sunday Overnight: Clearing. Strong northeasterly winds. Alpine temperatures around -25 C.

Monday: Mainly clear. Strong northeasterly winds. Alpine temperatures around -25 C.

Tuesday: Cold and clear. Light to moderate northeasterly winds. Alpine temperatures around -20 C.

Wednesday: Mainly cloudy, light flurries. Light to moderate northwesterly winds. Alpine temperatures around -15 C.

Avalanche Summary

Limited observations have been made with poor visibility, but we expect a natural avalanche cycle occurred on Saturday. During the peak of the storm on Saturday, several large natural storm slab avalanches were reported from treeline elevations in the Kakwa. 

On Thursday, operators in the Dezaiko range reported a skier-triggered storm slab avalanche on a northeast aspect in the alpine. This avalanche was remote-triggered, meaning the person was a distance away from where the slab initiated. 

Snowpack Summary

An intense storm over the past 3 days brought 20-100 cm of new snow to the region, with lightest amounts in the Pine Pass area, and heaviest amounts in the southwest ranges around McBride. This new snow overlies a widespread crust created from a rain event in early February. This 1-20 cm thick crust exists on all aspects and elevations, excluding areas in the high alpine in the south of the region that may remain crust-free. 

Below the crust, 10-40cm of more settled snow exists above the late January weak layer. This layer consists of weak faceted snow, a melt-freeze crust, and surface hoar crystals in isolated sheltered areas at treeline and below. The surface hoar has been increasingly hard to identify in the snowpack and has shown no reactivity in the past week. In many areas, this layer is bridged by the thick crust above it. 

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

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Closely monitor how the new snow is bonding to the crust.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.