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Avalanche Forecast

Archived

Feb 8th, 2020–Feb 9th, 2020

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

Regions

South Rockies.

5 to 15 cm of new snow + continued strong wind at upper elevations mean that many alpine slopes are likely primed for human triggered avalanches Sunday. We need to let the new snow settle and stabilize for a day or two before stepping out into complex terrain.

Confidence

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

Weather Forecast

Aside from a few bouts of potentially strong wind, we’re moving into a rather benign weather pattern for the foreseeable future.

SATURDAY NIGHT: Freezing level at valley bottom, light variable wind, no significant precipitation expected.

SUNDAY: A few clouds, freezing level rising to 1000 m, light southwest wind at lower elevations, potential for strong northwest wind at the highest elevations, no significant precipitation expected.

MONDAY: Clear skies, freezing level rising to 900 m in the afternoon, light variable wind, no significant precipitation expected.

TUESDAY: A few clouds, freezing level rising to around 1500 m in the afternoon, light southwest wind at lower elevations, potential for strong northwest wind at the highest elevations, no significant precipitation expected.

Avalanche Summary

Loose dry avalanches to size 1 were observed Thursday/Friday from extreme terrain, but aside from that, no significant avalanche activity has been reported since last weekend. 

There may have been some new storm slab/loose dry avalanche activity on Saturday, but that activity is expected to be on the smaller side and we have not received any reports yet.

A natural avalanche cycle during last weekend's storm included some large (size 2.5) deep persistent slab avalanches in the Elk Valley (see photos in this MIN report) that appear similar to avalanches in that area in mid-January, which suggests the deep persistent slab problem will continue to resurface during stormy periods.

Snowpack Summary

5 to 15 cm of storm snow from Friday Night/Saturday adds to the variable amounts of wind affected snow that sits above a widespread rain crust that exists up to roughly 2100 m. The Elk Valley has 5-20 cm of snow above the crust and the eastern slopes have 15-35 cm above the crust. There have been observations of surface hoar forming in the Elk Valley previous to Friday Night's storm, check that out here. A well consolidated mid-pack overlies generally weak basal facets, that may be possible to trigger in isolated shallow rocky start zones.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.

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.