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Avalanche Forecast

Archived

Dec 17th, 2018–Dec 18th, 2018

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

Regions

Northwest Inland.

We're lacking information about how reactive recent storm snow has been, so it's critical to make your own observations. Back off if you see recent avalanches, cracking, or whumpfing.

Confidence

Low - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Flurries with 2-10 cm of snow, strong wind from the southeast, freezing level around 700 m.TUESDAY: Scattered flurries with trace accumulations, moderate wind out of the southwest, freezing level climbing to 1000 m.WEDNESDAY: Mostly cloudy with isolated flurries, moderate wind from the southwest, freezing level drops to 500 m with alpine high temperatures around -6 C.THURSDAY: Cloudy, light wind from the southeast, freezing level drops to valley with alpine high temperatures around -8 C.

Avalanche Summary

On Sunday, recent slab avalanches, whumpfing, and cracking were observed in the Hankin area. Natural slab avalanches were also reported last week during the start of the stormy weather, including two large (size 2) avalanches on east-facing wind-loaded slopes near treeline (1700 m) and several smaller slabs in steep gullies at low elevations. See this MIN report from Ashman.Recent activity has likely been in the new storm snow and on the interface with old snow from the early December dry spell (which is roughly 40-70 cm below the surface).

Snowpack Summary

Stormy weather continues to build storm slabs and wind slabs throughout the region. Sunday's storm brought another 15-25 cm of snow, which brings the total amount of snow since last Tuesday (the 11th) to 40-70 cm. The combination of new snow and forecast strong south winds is likely forming thicker and more sensitive wind deposits at higher elevations. The storm snow may still need a bit more time to form a good bond with the weak surface hoar and facets that formed during the dry spell in early December. We're lacking information about the current strength of this layer.Deeper in the snowpack, there are reports of several crusts including an early season crust with facets near the bottom of the snowpack.

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.