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Avalanche Forecast

Archived

Dec 7th, 2019–Dec 8th, 2019

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

Regions

Northwest Coastal.

Caution as you transition into wind-exposed terrain. Avalanches are possible where wind slabs have formed in the alpine.

Share what you see in the mountains this weekend via the MIN!

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

We’re entering a rather quiet period with no significant snow expected until at least the middle of next week.

SATURDAY NIGHT: Freezing level at valley bottom, moderate to strong northwest wind, no significant precipitation expected.

SUNDAY: A few clouds, freezing level at valley bottom, moderate northwest wind, no significant precipitation expected.

MONDAY: A few clouds, freezing level at valley bottom, potential for an inversion setup with air temperatures near 0 C in the alpine, light southerly wind, no significant precipitation expected.

TUESDAY: Broken cloud cover, freezing level at valley bottom, strong southerly wind, no significant precipitation expected.

Avalanche Summary

There are two great MIN observations from the Shames backcountry, this one is from Friday, this one is from Saturday.

We have very limited observations combined with high regional variability from the recent storm. Wind slab avalanches up to size 2 were reported Thursday in the Bear River Pass area on lee terrain features in the alpine. As snowfall and wind tapers, these wind slabs may remain reactive to human-triggering.

If you get into the mountains this weekend, let us know what you see by submitting to the Mountain Information Network!

Snowpack Summary

Incremental snowfall over the last week has added a fresh coat to the backcountry. Accumulations have varied drastically by location, with favored areas picking up 45-60 cm of snow in the last week. The higher amounts fell further north in areas such as Bear Pass. Southwest winds have transported the recent snow into wind slabs on lee features at upper elevations. Depending on location, these slabs are likely sitting on a mix of sugary faceted snow, feathery surface hoar crystals, and hard wind-affected snow that may be reactive to human triggering.

Snowpack depths at treeline are likely in the 90-160 cm range, tapering quickly at lower elevations.

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.