Avalanche Forecast

Issued: Mar 20th, 2019 5:01PM

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

Avalanche Canada cgarritty, Avalanche Canada

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A natural avalanche cycle is underway. Travel in avalanche terrain is not recommended.

Summary

Confidence

Moderate -

Weather Forecast

Wednesday night: Clear. Light east winds. Freezing levels remaining near 3100 metres.Thursday: Sunny. Light east winds. Alpine high temperatures around +7 with freezing levels to 3200 metres, remaining elevated overnight.Friday: Sunny with cloud increasing overnight. Light northeast winds. Alpine high temperatures around +7 with freezing levels easing from 3200 metres to 1900 metres by mid-morning on Saturday.Saturday: Cloudy with wet flurries bringing up to 8 cm of new snow to higher elevations, light rain below about 1500 metres. Light northwest winds. Alpine high temperatures around 0 with freezing levels to 1900 metres.

Avalanche Summary

A report from Tuesday in the Elk Valley described numerous natural persistent slab releases reaching size 2 (large) on southeast aspects at around 2200 metres. Further to this activity, any sun-exposed snow became isothermal (slushy and cohesionless), and huge whumpfs that collapsed the basal snowpack were triggered during ski touring.A report from Sunday in the Window Mountain area described snowshoeing party choosing to turn back after avoiding a large loose wet avalanche that ran into below treeline terrain. This highlights the importance of considering overhead hazards being warmed by the sun and potentially inverted (warmer at higher elevations) temperatures.Given the above activity, loose wet avalanches remain a daily concern in steep, sun-exposed terrain (and in runout zones) while concern is increasing for deep basal snowpack weaknesses that have the potential to produce very large and destructive slab avalanches.

Snowpack Summary

Upper snowpack: Getting warm and moist during the day, likely forming weak crusts overnight that deteriorate during the day. On sunny aspects the upper snowpack has become increasingly isothermal (slushy and cohesionless) with successive days of warming. On lee slopes there may be buried hard layers of wind effected snow (buried wind slabs).Mid pack: The mid-snowpack consists of sugary faceted grains (facets) and layers of harder wind effected snow. Recent loose wet avalanches have been entraining additional mass by gouging into this faceted snow. These facets have also acted as a failure plane in recent slab releases.Lower pack: The strength of the lower snowpack is increasingly in question in shallower areas where the February cold was able to penetrate and weaken basal layers. Warm temperatures are increasing the strain on basal weaknesses each day. Basal snowpack and ground are evident in the start zones and tracks of many recent avalanches.It's a good time to stand aside and let the mountains shed their coat. Stability will improve greatly when temperatures cool off.

Problems

Loose Wet

An icon showing Loose Wet
Sunshine and warm temperatures will peel away layers or recent snow on sunny slopes as loose wet slides. Large loose wet avalanches can threaten lower elevation runout zones with very destructive debris flows.
Be aware of overhead hazards and avoid exposure to avalanche runout zones.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Expect shaded aspects to become increasingly prone to loose wet avalanche activity.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Numerous large deep persistent slab releases have resulted from ongoing warming and strong sunshine. The same stress test will be underway again on Thursday. Deep releases are most likely to occur in thin snowpack areas in the alpine.
Sustained warming is testing deeply buried weak layers. Recognize and avoid overhead hazards.Be aware of sun exposure changing from one aspect to the next over the day.Thin snowpack areas exposed to sun are likely to produce deep persistent slab releases.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3

Valid until: Mar 21st, 2019 2:00PM

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