Avalanche Forecast

Lizard Range and Flathead

Date issued

Jan 4, 2018 - 5:11 PM

Valid until

Jan 5, 2018 - 2:00 PM

Prepared by

mbender

Expect to continue to see persistent slab avalanche activity as the snow sitting above the persistent weak layer further settles and consolidates with forecast warmer temperatures. Adopt a conservative approach in the coming days.

Regular season
Thursday - January 4, 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

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.

Friday - January 5, 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

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.

Saturday - January 6, 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

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.

Avalanche Problem 1: Persistent Slabs

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

A weak layer composed of surface hoar and/or crusts is buried 40-70 cm below the surface. This layer continues to reactive.

Travel and Terrain Advice
  • Watch for whumpfing, hollow sounds, and shooting cracks.
  • Choose supported slopes without convexities at treeline where buried surface hoar may be preserved
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Avalanche Problem 2: Wind Slabs

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

Moderate winds have created fresh wind slabs in the alpine.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • 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 Summary

On Thursday there was a report of skier triggered avalanche in Orca bowl involving a group of 11 with 6 people caught and partially buried. This was a size 2 avalanche occurring on a northeast aspect at 1975m and reportedly running as a windslab sitting on a crust.

Additionally there have been several natural avalanches between 1600m and 1800m on steep or open glades on all aspects. This is where the mid-December layer has been most active.

Snowpack Summary

A persistent weak layer buried mid-December is buried 40-70 cm below the surface. This layer can be found in a variety of locations, but most commonly can be found between 1600m and 1800m and consists of crusts on south and west facing slopes and feathery surface hoar in sheltered areas at and below tree line. It has been producing sudden results in recent snowpack tests.

At higher elevations, wind has modified the snow pack creating a stiffer snow on top of softer snow condition. The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November. This crust has been reported to be unreactive, however it is possible that it may have been the bed surface for a skier triggered avalanche that happened on Thursday (See Avalanche Activity section below for details).

Weather Forecast

FRIDAY: Cloudy with isolated flurries, accumulation 3-5cm / Light southwest wind / Alpine temperature -3

SATURDAY: Cloudy with isolated flurries and sunny breaks / Light to moderate southwest wind / Alpine temperature -4

SUNDAY: Cloudy with flurries / Light to moderate west wind / Alpine temperature -5

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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