Avalanche Forecast

Northwest Inland

Date issued

Jan 29, 2018 - 4:37 PM

Valid until

Jan 30, 2018 - 2:00 PM

Prepared by

mbender

New snow and wind will continue to build wind slabs in the alpine and tree line elevations. Triggering persistent slabs from thin snowpack areas remains a concern in the north of the region.

Regular season
Tuesday - January 30, 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.

Wednesday - January 31, 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.

Thursday - February 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

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: Wind Slabs

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

Wind slabs can be found on leeward aspects in the alpine as well as wind-exposed areas at treeline. These slabs overlie a thin crust/ surface hoar layer and have been reactive to light triggers especially in steep or convex terrain near ridge crests.

Travel and Terrain Advice
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
  • Be cautious as you transition into wind affected terrain.

Avalanche Problem 2: Persistent Slabs

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

Weak layers buried in the snowpack have produced recent avalanches particularly on unsupported features.

Travel and Terrain Advice
  • Watch for signs of instability such as whumpfing, or cracking at lower elevations.
  • Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.

Avalanche Summary

Most recent avalanche activity has been reported as loose dry surface snow sluffing to size 1 in steep terrain.

Friday there was a report of a helicopter remotely triggering a Size 2.5 wind slab from above the slope on a west aspect at 1500 m north of Kispiox. Thursday there was a report of skiers, north of Kispiox, remotely triggering a Size 2-2.5 avalanche from a safe location on a ridge that released on the adjacent slope on a northwest aspect at 1650 m. A weak layer buried late-December was the suspected failure plane.

Snowpack Summary

30-70cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and tree line elevations.

Below, there are two separate crust and/or surface hoar layers that were buried late-December and mid-December. They are 50-80 cm below the surface. In the past week these deeper layers have produced hard but sudden results in snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Weather Forecast

TUESDAY: Isolated flurries, accumulations 5-10cm Monday night into Tuesday / Moderate to strong southwest wind / Alpine temperature -5

WEDNESDAY: Isolated flurries / Light to moderate southwest wind / Alpine temperature -7

THURSDAY: Isolated flurries / Light to moderate south wind / Alpine temperature -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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