Avalanche Forecast
Regions: Howson, Kitimat, Nass, Northwest Coastal, Rupert, Seven Sisters, Shames, Stewart, West Stikine.
Avoid all avalanche terrain! Another natural avalanche cycle is expected in the region on Thursday.
Confidence
High
Avalanche Summary
Evidence of a widespread natural avalanche cycle was observed throughout the region on Monday and Tuesday, with storm slabs and wind slabs observed to an impressive size 3 (very large). Many slabs started off dry but finished running as wet loose slides at the bottom of their runouts.
A MIN from Monday at Shames gives some great mid-storm observations.
This activity should serve as an indication of what's on tap for this next storm pulse.
Snowpack Summary
Forecast heavy snowfall and strong to extreme winds will take over the upper snowpack again Wednesday night through Thursday, building new storm slabs at all elevations.
The new snow will overshadow the 15-40 cm (diminishing with elevation) that constituted our latest storm snow settling over supportive melt-freeze crust found up to 1800m and on all elevations on steep solar slopes. South to southwesterly winds have been creating wind affected surfaces and wind slabs of varying age and reactivity on an ongoing basis.
Recent and forecast storm snow will form only the uppermost fraction of the impressive 100-150 cm of storm snow from the past week that is collectively settling over a layer of facets, crust, and previous wind-affected surfaces in alpine terrain. This interface remains somewhat in question under the patterns of continuous loading and successive natural avalanche cycles.
The mid and lower snowpack continues to bond and stabilize while a number of buried weak layers are still being tracked by professionals in the region, having produced a few large avalanches in the not-too-distant past.
Weather Summary
Wednesday night
Heavy snowfall beginning with 15-30 cm of new snow by morning. Strong to extreme south winds.
Thursday
Cloudy with continuing heavy snowfall bringing another 20-40 cm of new snow. Strong to extreme south winds, easing over the day. Treeline high temperatures around -2 with freezing levels rising to about 700 m, possibly a bit higher.
Friday
Still mainly cloudy as easing flurries leave a final less-than-5 cm of new snow. Storm totals of around 40-70 cm. Light to moderate southwest winds. Treeline high temperatures around -3 and falling over the day.
Saturday
Cloudy with another round of flurries bringin 5-10 cm of new snow. Strong to extreme southwest winds easing over the day. Treeline high temperatures around -3.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Don't let the desire for deep powder pull you into high consequence terrain.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- Avoid exposure to overhead avalanche terrain during periods of heavy loading from new snow, wind or rain.
Avalanche Problems
Storm Slabs
Another round of heavy snowfall is expected to trigger yet another natural avalanche cycle involving large storm slabs and wind slabs on Thursday. With mid-storm interfaces still in the midst of healing up, there's a distinct chance of Thursday's avalanches failing deeper than the new snow interface.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely - Certain
Expected Size: 1 - 3
Persistent Slabs
A deeply buried weak layer still presents a Low Probability/High Consequence situation. New snow and wind has been testing this weakness in the snowpack and the results still aren't in. This layer would be most likely to be triggered in places where the snowpack is shallow and rocky.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5