Avalanche Forecast

Northwest Coastal

Date issued

Jan 18, 2018 - 5:00 PM

Valid until

Jan 19, 2018 - 2:00 PM

Prepared by

cgarritty

Be observant of wind effect as you transition to higher elevations. Expect storms slabs to be more reactive in wind affected terrain.

Regular season
Thursday - January 18, 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

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.

Friday - January 19, 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

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.

Saturday - January 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.

Avalanche Problem 1: Storm Slabs

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

Thursday's new snow and southwest winds formed fresh storm slabs. Slabs are likely to be touchiest in wind affected areas, and particularly in the immediate lee of ridgecrests and exposed terrain features.

Travel and Terrain Advice
  • Use ridges or ribs to avoid steep pockets of wind loaded snow.
  • Use extra caution in lee areas. Slabs will be touchier where wind loading has occurred.
  • The new snow will require several days to settle and stabilize.

Avalanche Summary

Reports from Thursday showed ski cutting producing loose wet releases to Size 1 in steep terrain in the Shames area. Several older Size 1.5 natural storm slab releases were also noted.  Looking forward, the storm slabs that formed over Thursday may remain reactive to human triggering on Friday. This concern will be greatest in wind affected areas at higher elevations.

Snowpack Summary

Snowfall over Wednesday and Thursday brought about 20 cm of new snow to the region. Moderate southwest winds over Thursday promoted storm slab formation at higher elevations and particularly in lee areas subject to wind loading. The new snow has buried a mix of old wind slabs and temperature crusts left over from the weekend. Professionals have been monitoring a few layers in the upper snowpack, including crusts and surface hoar layers buried 40-80 cm below the surface. Although these layers have been reactive in recent snowpack tests, they have not produced avalanches lately. The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.

Weather Forecast

Friday: Mainly cloudy. Light east winds. Alpine high temperatures to -3

Saturday: Cloudy with scattered flurries bringing 2-5 cm of new snow. Light to moderate southeast winds. Alpine high temperatures to -5.

Sunday: Cloudy with isolated flurries and a trace of new snow. Moderate east winds. Alpine high temperatures of -6.

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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