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Avalanche Forecast

Archived

Nov 28th, 2020–Nov 29th, 2020

Alpine
Natural and human triggered avalanches likely.
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 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.

Regions

Northwest Inland.

A bit of snow and strong wind may give way to a natural avalanche cycle Sunday that is expected to be confined to alpine and treeline elevations. With so little data coming from the region a conservative approach is recommended, even at lower elevations.

Confidence

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

Weather Forecast

An upper low in the Gulf of Alaska will send a frontal wave into the Northwest Inland Saturday through Sunday night delivering copious southwest wind and a bit of snow.

SATURDAY NIGHT: Freezing level near valley bottom, strong to extreme southwest wind, 5 to 10 cm of snow expected. 

SUNDAY: Overcast, freezing level between 500 and 1000 m, strong to extreme southwest wind, 5 to 15 cm of snow expected during the day with potential for another 5 to 10 cm of snow Sunday Night.

MONDAY: Scattered cloud cover, freezing level around 600 m, moderate to strong west wind, trace of snow expected.

TUESDAY: Overcast, freezing level climbing, potentially as high as 1500 m in the afternoon, strong to extreme southwest wind, trace of snow possible.

Avalanche Summary

New snow and wind Saturday night into Sunday night is expected to form fresh storm slabs at and above treeline.  

Observations are limited but the combination of snow and wind over the past few days has almost certainly formed wind slabs in open terrain. On Thursday there were reports of some small (size 1) wind slabs on wind-loaded east aspects.

Please submit your observations to the Mountain Information Network!

Snowpack Summary

A good shot of snow and wind are on the way, and it's unclear what this snow will be coming to rest on as observations for the region are incredibly limited.  

Over the last week storms delivered moderate amounts of snow (5 cm around Smithers and up to 20 cm further west) with strong wind from the southwest. Expect heavily wind affected snow in open terrain and watch for unstable slabs on slopes that have been loaded by the wind. Snowpack depths range from 60 cm in eastern parts of the region up to over 100 cm in western parts of the region. Lower elevation terrain may still be below the threshold for avalanches. Reports suggest the bottom half of the snowpack consists of crusts, and in some cases some weak snow may be developing around these crusts. This will be a layer to monitor as the season progresses.

Terrain and Travel

  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • Be careful as you transition into wind affected terrain.
  • Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.

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.