Date issued

Jan 2, 2018 - 8:03 AM

Valid until

Jan 3, 2018 - 8:00 AM

Prepared by

ross campbell

There is lots of uncertainty what's going to happen today as temperatures rise. Slab properties will change over the December 15th persistent weak layer, and a skier or rider could be the trigger needed to start a slab avalanche.

Regular season
Monday - January 1, 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

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 - January 2, 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

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.

Wednesday - January 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

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

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.

Avalanche Problem 1: Persistent Slabs

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

The December 15 surface hoar layer is widespread around treeline and buried 60cm. Cold temps have kept the slab from gaining cohesion, but today's warming trend may make it more reactive especially on steep unsupported terrain.

Travel and Terrain Advice
  • Watch for signs of instability such as whumpfing, or cracking.
  • Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Avalanche Problem 2: Loose Dry

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

We may see a natural loose dry cycle on steep solar aspects today, with solar radiation and an inversion. The combination of a loose sluff, plus a skier or rider could be the load for a step-down slab avalanche to the Dec 15th persistent weak layer.

Travel and Terrain Advice
  • Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.
  • Avoid thin, rocky or unsupported slopes.

Avalanche Summary

There have been no significant avalanches observed or reported in the last few days in Glacier National Park, with many of the standard lines been skied. Our Neighbors have seen more avalanches of late, due to either more load and slab formation or a shallower snowpack resulting in poor bonding between layers. We may see a change today!

Snowpack Summary

The snowpack is quite a mixed bag of layering depending on Aspect and Elevation. The Dec 15th PWL (most prominent at TL) is the main layer on our radar, and we're still waiting for it to really produce a decent cycle. We've observed some failures of this layer "cracking" giving the snowpack a rippled effect, but still not failing as an avalanche.

Weather Forecast

The main story for today and into the near future is the temperature inversion. Steep solar aspects in the alpine will see the most effect, while valley bottoms will stay cold and continue to facet. The inversion is set to last until Friday, when a low-pressure system slides in from the Pacific, pushing out the high pressure.

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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