Avalanche Forecast

Archived

Apr 8th, 2017–Apr 9th, 2017

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, 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 Coast Inland.

There is distinct variability in avalanche conditions between the north and south of the region. In the north of the region recent heavy loads such as cornice falls have been sporadically triggering full depth avalanches.

Confidence

Low - Due to the number of field observations

Weather Forecast

SUNDAY: Mix of sun and cloud / Light south wind / Alpine temperature -3 / Freezing level 1400mMONDAY: Cloudy with scattered flurries / Moderate southwest wind / Alpine temperature -2 / Freezing level 1400mTUESDAY: Mix of sun and cloud / Light to moderate east wind / Alpine temperature 0 / Freezing level 1600m

Avalanche Summary

There have been very limited information sources reporting in the latter half of this week from the north of the region. A Mountain Information Network post from Monday describes a cornice triggered avalanche stepping down to the November deep persistent weak layer or ground in the alpine on a North aspect. Click here to read more details in the post itself. An additional report from Monday indicates a size 2.5 explosives controlled cornice failure stepping down to what was suspected to be a mid-February persistent weak layer in the Duffy Lake area. Yet another report from the same area indicates a size 3 large explosives triggered avalanche stepping down to what was suspected to be a November persistent weak layer. There have been no new avalanche reports from the Coquihalla area or south of the region in the past several days.Recently formed wind slabs are expected to remain reactive to human triggering.

Snowpack Summary

Anywhere from 15-25cm of new snow is sitting on a widespread melt-freeze crust that exists on all aspects and elevations except for high elevation north facing terrain. Recent moderate winds from the south have formed new wind slabs in the alpine and have added load to cornices. On sun exposed slopes and at lower elevations, several crusts likely exist in the upper snowpack which are generally well bonded. Both the mid February persistent weak layers and November deep persistent weak layer seemed to have become reactive to heavy loads (cornice falls and/or large explosives triggers) earlier in the week at upper elevations in the northern part of the region near Duffey and Birkenhead Lakes.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.