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Avalanche Forecast

Archived

Dec 25th, 2017–Dec 26th, 2017

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

Olympics.

Wind slabs, or storm slabs that may have formed last week should continue to stabilize Tuesday. Avoid steeper terrain features with firmer wind transported snow. Use extra caution when transitioning into potentially wind affected terrain.

Detailed Forecast

Brief high pressure should rebuild along the PNW coastal areas Tuesday. This should provide a gradual clearing trend over the Olympics, with generally light winds and cool temperatures.

This weather should allow for continued gradual settlement of any recent storm layers or wind slabs in higher exposed terrain. However, cool temperatures will help slow this process and may preserve wind slabs in higher terrain.

Watch for wind stiffened snow on a variety of aspects, including non-traditional aspects from recent northerly winds

Early season hazards still exist at lower elevations and especially around creek beds that are not filled in.

Snowpack Discussion

A weak disturbance moved across the Olympics Christmas Eve depositing 2-4 inches of new snow, with light winds recorded at Hurricane Ridge. 

About 18 inches fell at Hurricane Ridge ending early Wednesday last week. Strong winds during this storm built unstable wind and storm slabs.

Cool and fair weather allowed this snow to mostly stabilize midweek resulting in a decreasing avalanche danger over the past several days.

In general about two feet of snow now sits on the old snow surface from a week ago.

Observations

NWAC pro observer Matt Schonwald was at Hurricane on Saturday and reported evidence of north to east winds but no wind slab or significant shear in the upper snowpack. The structure was generally F over 4F with good bonds to the Thanksgiving crust.

A nice observations Friday via the NWAC Observations page indicated about 2-3 feet of snow above the variable surfaces from early December's high pressure. Tests gave stubborn results for storm slab and there were no natural or triggered avalanches noted.

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.