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Avalanche Forecast

Archived

Dec 26th, 2018–Dec 27th, 2018

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

Still feels a lot like Christmas; great skiing, decent visibility, and a moderate avalanche hazard. There are still some concerns on specific terrain features, travel accordingly.

Weather Forecast

A mix of sun and cloud with a trace of snow, we'll see an alpine high of -11°c, and light winds from the South. Continued cool temperatures with light winds and isolated flurries tomorrow, freezing levels should remain at valley bottom. On the weekend it will warm up and start snowing; forecasts are showing 30+cm should fall by Monday morning.

Snowpack Summary

Over half of our snow pack can be attributed to the steady 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

On Christmas day we observed 3 size 2 wind slabs in the HWY corridor on North aspects out of very steep terrain. No new observations from the back country yesterday. There is a significant 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.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.