Avalanche Forecast

Issued: Mar 27th, 2019 4:20PM

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

cgarritty, Avalanche Canada

Purcells.

A variable dose of new snow has resupplied avalanche problems in much of the region. Be mindful of avalanche danger increasing in sync with daytime warming.

Summary

Confidence

High -

Weather Forecast

Wednesday night: Mainly cloudy. Light to moderate southeast winds.Thursday: A mix of sun and cloud. Light variable winds. Alpine high temperatures around -2 with freezing levels to 1900 metres.Friday: Mainly sunny. Light northeast winds shifting northwest. Alpine high temperatures around 0 with freezing levels to 2100 metres.Saturday: Mainly sunny with cloud increasing over the day. Light southwest winds. Alpine high temperatures around 0 with freezing levels to 2100 metres.Overnight freezing levels will increase steadily during this period, dropping briefly each night to between 1000 to 1500 metres.

Avalanche Summary

No new avalanches were reported in the Purcells on Tuesday, but reports from neighbouring regions showed new snow from Tuesday's storm reacting to skier traffic, ski cutting, and explosives control with 10-25 cm-deep slabs propagating easily and widely over previous surface crusts. All aspects were represented in reports, with a focus on north to northeast aspects as a result of loading by southwest winds. Similar conditions are likely to exist in areas of the Purcells that received more than a skiff of new snow from Tuesday's storm. Looking forward, lingering wind slabs (in areas with new snow) may still react to skier triggering and may also become touchier with warming. In some areas an ample supply of new snow is in place to reinvigorate loose wet avalanche problems as sunshine and warming take hold each day. Where less new snow exists, loose wet activity may be slightly more subdued.

Snowpack Summary

Variable new snow amounts of a trace to 25 cm have accumulated above a surface of melt-freeze crust in most areas above 1500 metres. Below this elevation it buried variably moist or crusty surfaces. Precipitation as rain has continued to saturate the snowpack that is increasingly isothermal (slushy and cohesionless) and disappearing rapidly below about 1100 metres.The mid snowpack is generally consolidated and strong, but exceptions may exist on north aspects above 2000 m, where a gradually strengthening layer of faceted grains buried 40 to 60 cm deep may still be preserved below an overlying slab of old and hard wind-affected snow.The base of the snowpack is composed of weak faceted snow which may coexist with a melt-freeze crust. Only one very large persistent slab was reported to have failed at this layer during last week's warming event.

Problems

Loose Wet

New snow has resupplied our loose wet avalanche problem in much of the region. Rising temperatures and sunshine will destabilize surface snow on Thursday, especially on steep, sunny slopes. Larger avalanches become possible during peak warming.

This problem may affect shaded aspects where air temperatures exceed 0 degrees.Start and finish early to reduce your exposure to avalanche terrain during the heat of the day.Avoid exposure to terrain traps, where the consequences of a small avalanche could be serious.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Wind Slabs

New snow and south winds formed new wind slabs at higher elevations during the storm. This problem increases with elevation and is highly variable throughout the region with new snow totals of a trace to 25 cm.

Use ridges or ribs to avoid pockets of wind loaded snow.Be careful around wind loaded pockets near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Persistent Slabs

A few weak layers still exist within the snowpack. The recent hot weather may have influenced these layers, but time is needed to assess how much they have changed.

Avalanche hazard may have improved, but be mindful that buried instabilities are still present.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Best to avoid thin, rocky terrain, where it may be easier to trigger deeper weak layers.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

1.5 - 2.5

Valid until: Mar 28th, 2019 2:00PM