Avalanche Forecast

Issued: Nov 23rd, 2018 5:06PM

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

cgarritty, Avalanche Canada

Purcells.

A tricky snowpack is already taking shape in the Purcells. Continue to gather information as you travel and be sure to increase caution if you're venturing into the alpine.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Friday night: Mainly cloudy with light north winds.Saturday: Mainly cloudy. Light northwest winds. Alpine high temperatures around -8.Sunday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures warming to around -4.Monday: Mainly cloudy with scattered flurries bringing a trace to 10 cm of new snow. Light to moderate southwest winds. Alpine high temperatures of -2 as freezing levels rise to around 1500 metres.

Avalanche Summary

Skiers and explosives have recently triggered small wind slabs in cross-loaded and lee terrain features at treeline and alpine elevations. Earlier in the month, a natural avalanche cycle took place over the late October crust/facet combination. Be aware of the continued possibility for smaller avalanches to 'step down' or even initiate at this deeper layer.

Snowpack Summary

Light snowfall over Thursday and Friday buried a widespread layer of weak, feathery surface hoar crystals with about 5-10 cm of new snow. Reports from several points in the region show this surface hoar sitting above a layer of recently reactive wind slab that was created by strong winds earlier this week. This wind slab layer overlies yet another widespread layer of surface hoar from mid-November, now found about 20-40 cm deep. A final, prominent feature of the snowpack is a combination of a melt-freeze crust and underlying sugary, faceted snow found around the base of the snowpack. Avalanches have been triggered where there is a slab above this crust.

Problems

Wind Slabs

Recently formed wind slabs may remain reactive to human triggering on Saturday. These slabs may also be obscured by recent snowfall.

Be careful around wind loaded pockets, especially near ridge crests and roll-overs.Examine slopes for patterns of wind transport as you enter wind-exposed terrain.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Deep Persistent Slabs

A nasty combination of crust and sugary, faceted snow exists at the base of the snowpack in the alpine. This weak layer has already produced large avalanches and may be triggered by the weight of a person, machine, or wind slab release.

Choose increasingly mellow slopes as you approach alpine elevations.Be highly suspicious of slopes that show signs of previous avalanching.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 2.5

Valid until: Nov 24th, 2018 5:06PM