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Avalanche Forecast

Archived

Nov 25th, 2019–Nov 26th, 2019

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

Regions

South Columbia.

Riding quality is good, but wind slabs are sensitive to human triggering at and above treeline to size 2. Below treeline the new snow rests on a touchy layer of surface hoar, so steep unsupported features, rolls, creek bottoms and terrain traps are all suspect.

Confidence

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

Weather Forecast

After a stormy weekend we’re transitioning to clearing skies, colder temperatures and no significant precipitation for the foreseeable future.

MONDAY NIGHT: Freezing level at valley bottom, light variable breeze, no significant precipitation expected.

TUESDAY: Scattered cloud cover, freezing level at valley bottom, light east wind, no significant precipitation expected.

WEDNESDAY: A few clouds at dawn building to broken cloud cover in the afternoon, freezing level at valley bottom, light to moderate east/northeast wind, no significant precipitation expected.

THURSDAY: A few clouds, freezing level at valley bottom, light east wind, no significant precipitation expected.

Avalanche Summary

Observations are lean right now, but the weekend snow combined with wind out of the south & southwest to form wind slabs near ridge crest that have been sensitive to human triggering up to size 1.5. This MIN post has a great photo that is pretty representative to what we're envisioning. If you've been out recently please let us know what you're seeing on the MIN. We're particularly interested in learning how widespread and sensitive the wind slab problem is. Any observations of avalanches below treeline or just a general update on the state of the surface hoar in the trees would also be fantastic. Thanks! 

Snowpack Summary

Early season conditions are highly variable. Snow line begins around 1200 m, and the snowpack depth ranges from 50 cm to 150 cm.

The weekend storm produced 20 to 35 cm of snow accompanied by strong west/southwest wind. On steep south facing slopes in the alpine the new snow rests on a crust. A crust is also present on all aspects below 1600 m and many locations have surface hoar on top of the crust.

Crusts that formed in late October are now buried 50 to 90 cm deep. We're working off of a short list of observations, but this late October crust layer is highly variable and may be associated with both surface hoar and facets. This is a layer to watch over the next week as unlimited visibility and good travel conditions begin to sing the Alpine's siren song.

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.