Avalanche Forecast

Northwest Inland

Date issued

Apr 1, 2018 - 4:18 PM

Valid until

Apr 2, 2018 - 2:00 PM

Prepared by

mconlan

New and old slabs are taking their time to bond to underlying layers. Be cautious on southerly aspects when the sun is out -- it could weaken the snow and trigger avalanches.

Regular season
Sunday - April 1, 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

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.

Monday - April 2, 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

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.

Tuesday - April 3, 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.

Avalanche Problem 1: Storm Slabs

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

Recent storm slabs are found in the south of the region and older slabs exist in the north.  Very large avalanches have occurred, as the snow is not bonding well to underlying layers of surface hoar, crusts, or sugary facets in thin snowpack areas.

Travel and Terrain Advice
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.
  • Observe for signs of instability, such as cracking, whumpfing, and avalanche activity.
  • Approach lee and cross-loaded slopes with caution.

Avalanche Summary

On Saturday, a large persistent slab avalanche was reported in the north of the region, failing on the early-March weak layer described in the Snowpack Discussion.  It failed on an easterly aspect around treeline.  Portions of the avalanche stepped down to sugary facets near the bottom of the snowpack.

Otherwise, there was further evidence of the natural cycle that occurred on Friday within the recent storm snow, with storm slab and loose dry avalanches.  They were small to large (size 1 to 2.5), on all aspects, and at all elevations.

Snowpack Summary

Expect to find a surface crust on southerly aspects from the weekend’s clear skies.

A reactive slab about 50 cm thick has developed from last week’s storm snow.  This slab overlies two layers of weak surface hoar, which exist on shaded aspects at high elevations.  The slab sits on a melt-freeze crust on all aspects below treeline.  The storm snow may still be loose in sheltered and shady locations.

Near the bottom of the snowpack, weak and sugary facets are found in shallow, rocky snowpack areas.  Storm slabs have stepped down to these facets recently, producing very large avalanches.

Weather Forecast

MONDAY: Partly cloudy, light southerly winds, alpine temperature -12 C, freezing level 400 m.

TUESDAY: Mostly cloudy with light snowfall, accumulation 2 to 5 cm, light to moderate southerly winds, alpine temperature -11 C, freezing level 500 m.

WEDNESDAY: Mostly cloudy with light snowfall, accumulation 1 to 3 cm, light southerly winds, alpine temperature -10 C, freezing level 500 m.

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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