Avalanche Forecast

North Columbia

Date issued

Mar 20, 2018 - 5:01 PM

Valid until

Mar 21, 2018 - 2:00 PM

Prepared by

cgarritty

Your hunt for sheltered snow is likely to lead you to the same areas where storm slabs are a concern. Stick to supported slopes to limit your exposure.

Regular season
Tuesday - March 20, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Wednesday - March 21, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Thursday - March 22, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Avalanche Problem 1: Storm Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Isolated pockets of surface hoar on sheltered, high north aspects have led to prolonged reactivity in storm slabs about 30 cm deep. Isolated wind slabs and mature cornices are other hazards to manage at higher elevations.

Travel and Terrain Advice
  • Give cornices a wide berth when travelling on or below ridges.
  • Use extra caution in the afternoon if snow becomes moist or wet.
  • Be cautious around steep or convex slopes where buried surface hoar may be preserved.

Avalanche Summary

Reports from Sunday included a remotely (from a distance) triggered 25 cm deep storm slab (size 1) releasing with skier traffic on a steeper north-facing slope at around 2000 m in the Monashees. Several more natural size 2 storm slab releases were observed on very steep northeast-facing terrain at around the same elevation. These occurred during the peak of daytime warming.

On Saturday there were numerous reports of size 1-2, loose wet avalanches on sunny, solar aspects involving the recent storm storm snow, as well as one report of a size 1.5 skier triggered slab (30 cm deep) on a northwest aspect at 2000 m.

Last Friday there were reports of several skier triggered (size 1-1.5) avalanches from 15-25 cm deep on north through southeast aspects between 1700-2100 m.

Snowpack Summary

Recent light snowfalls have been followed by warm daytime temperatures and glimpses of sun, setting up a couple of thin storm snow layers over temperature and sun crusts at lower elevations and on south aspects. On shaded aspects at higher elevations, these snowfalls have buried and preserved a couple of surface hoar layers now found up to 30 cm deep. The deepest of these surface hoar layers has been the failure plane in several recent slab avalanches.

New snow amounts taper with elevation and below 1800 m, minimal accumulations have buried a supportive crust on all aspects. This crust will likely break down with daytime warming, becoming moist in the afternoon.

Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, large cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.

Weather Forecast

Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate southeast winds, increasing overnight. Freezing level to 1600 metres with alpine high temperatures around -4.

Thursday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Moderate to strong southeast winds. Freezing level to 2100 metres with alpine high temperatures around 0 to +1.

Friday: Mainly cloudy with continuing isolated flurries and a trace of new snow. Light to moderate southwest winds. Freezing level to 1300 metres with alpine high temperatures around -7.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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