Archived

Avalanche Forecast

Dec 27th, 2018–Dec 28th, 2018

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Glacier.

The likelihood of triggering a slab is relatively low, but the consequences are high! Even a small avalanche in the wrong terrain feature can have penalties.

Weather Forecast

A mix of sun and cloud today; the alpine will reach -11c, and winds may change direction to the NW. Continued cool temps with light winds and flurries tomorrow, fl will remain at valley bottom. On the weekend it will warm up and start storming; forecasts are showing 20+cm should fall by Monday morning accompanied by strong SW winds.

Snowpack Summary

Over half of our snow pack can be attributed to recent December snowfalls. Pockets of wind slab are lingering in lee features and cross loaded slopes in the alpine and treeline. The Dec 9 and Nov 21 interfaces are down ~100-120cm and still producing Hard and Sudden test results. We have no persistent weak layers in the upper snowpack.

Avalanche Summary

No new significant avalanches have been observed in the HWY corridor, or reported from the back country in several days. There is a interesting MIN report from just east of Glacier National Park from the 23rd of Dec. Snowmobile triggered size 2.5-3 deep slab avalanche on a NW aspect near Silent Pass.

Confidence

Due to the number and quality of field observations

Avalanche Problems

Wind Slabs

We have minimal observations from alpine terrain and have concerns of lingering pockets of wind slab; especially in immediate lee features below ridge crests and on cross-loaded slopes. Use caution and tread carefully entering new terrain.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

The Dec 9 and Nov 21 persistent weak layers are down ~100-120cm and consists of surface hoar, facets, or a sun crust depending on aspect and elevation. Human triggered avalanches on these layers are unlikely but still possible.

Avoid thin, rocky or unsupported slopes.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3