Avalanche Forecast

Issued: Nov 23rd, 2012 9:04AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Wind Slabs and Persistent Slabs.

triley, Avalanche Canada

Northwest Coastal.

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the forecasters blog for further details on interpreting early season bulletins.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Overnight and Saturday: Strong SE winds overnight are expected to ease to moderate with strong gusts during the day Saturday. Alpine temps should lower to about -9.0 and remain cool through Sunday. Expect 5-7 mm overnight and an additional 8-12 mm on Saturday.Sunday: High pressure is moving on to the coast, but it looks like it will remain mostly overcast with some convective snow showers. Winds are expected to switch to the NW and remain moderate with strong gusts.

Avalanche Summary

Some touchy thin wind slabs 5-15 cms have been reported to be releasing in the new snow where it has been transported into a wind slab. Explosives control last weekend produced a couple of 30cm deep size 1.5-2 storm slab avalanches. Natural avalanche activity followed by human-triggered activity generally occurs with every intense weather period, such as what's forecast for Thursday night and Friday.

Snowpack Summary

Total snowpack depth are probably close to a metre in most treeline areas and deeper but more variable in the alpine, while below treeline areas are probably still below threshold depths for avalanches. A recent profile at 1200m in the Shames area showed a predominately "right-side-up" 120cm deep snowpack with a thin layer of facets sitting on a crust 35cm off the ground. An Extended Column Test produced produced easy (10 taps)Â results on this persistent weak layer , but the resistant fracture didn't propagate across the entire column. Check out the Skeena/Babine discussion forum for more information from the area.

Problems

Wind Slabs

Recent northerly and easterly winds have deposited weak slabs on unusual aspects. Natural avalanche activity is expected in response to heavy wind-loading, and fresh wind slabs will likely be sensitive to human triggering.

Avoid freshly wind loaded features.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Facet/crust combinations can propagate over large areas, are often prone to remote triggering and step down avalanches, and typical trigger points include thin rocky areas.

Choose conservative lines and watch for clues of instability.>Choose regroup spots that are out of avalanche terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Nov 24th, 2012 2:00PM