Avalanche Forecast

Northwest Inland

Date issued

Jan 30, 2018 - 4:27 PM

Valid until

Jan 31, 2018 - 2:00 PM

Prepared by

shorton

New snow and wind will continue to build wind slabs in the alpine and treeline 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 lee aspects in the alpine and wind-exposed areas at treeline. They overlie a thin crust / surface hoar layer and have been reactive to light triggers.

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

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

Avalanche Summary

Most of the recent reported activity has been loose dry surface snow sluffing in steep terrain. On Monday, a large size 3 slab avalanches was reported on an east aspect at 1900 m in the Howsons.

On Friday, a helicopter remotely triggered a size 2.5 wind slab from above the slope on a west aspect at 1500 m north of Kispiox. On Thursday, skiers north of Kispiox remotely triggering a size 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

Strong winds have built wind slabs in exposed terrain. 30-60 cm 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 treeline elevations.

Below, there are two crust and/or surface hoar layers that were buried in 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

WEDNESDAY: Isolated flurries with accumulations of 5-10 cm / light to moderate southwest wind / alpine temperatures around -8 C.

THURSDAY: Isolated flurries / light to moderate south wind / alpine temperatures around -10 C.

FRIDAY: Flurries with accumulations of 10-15 cm / moderate southwest wind / alpine temperatures around -12 C.

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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