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Avalanche Forecast

Archived

Jan 14th, 2018–Jan 15th, 2018

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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Older settling wind slabs my linger in higher shaded terrain Monday. An overnight refreeze, followed by clouds and cooling winds should limit the danger on Monday. Monitor surface snow conditions, and watch for surface snow becoming wet more than the top inch or two.  

Detailed Forecast

Mostly clear skies followed by increasing high clouds late Sunday night should allow for the surface snow to again form a crust, though likely not supportable.

Increasing clouds and moderate south winds and warm temperatures are expected during the day Monday. This should allow for slowly weakening surface snow, however wind and clouds should limit the surface snow melt to just a few inches at most.

Older wind slabs formed late last week will continue to strengthen, but may linger above treeline, especially on steep shaded slopes below ridges. Identify and avoid locations where avalanches are more likely triggered, such as unsupported slopes, steep convex roles, below cornices, and other shallow locations within the snowpack.

Monitor changes in surface snow conditions throughout the day, especially in areas void of a surface crust. It only takes a few inches of wet surface snow to avalanche.

Snowpack Discussion

Clear skies Saturday night allowed for a moist upper snow pack to re-freeze in most areas, forming a breakable surface crust by Sunday morning. 

Mild weather over the weekend and abundant sunshine near and above treeline allowed for lingering storm and wind slabs from last week’s storms to gain strength. 

Cooler and cloudy weather in the lower elevations limited surface snow melt and maintained firm settled storm snow.

The very mild air temperatures and sunshine over the weekend has allowed moist to wet surface snow conditions to develop during the day, especially higher terrain sun exposed terrain.

Last week’s storms brought 8-14 inches of snow to the east slopes of the Cascades. Winds throughout the storm periods redistributed snow, forming wind slabs on a variety of aspects especially in exposed terrain that continue to strengthen over the past several days.

A supportive crust (1/5) formed from a widespread freezing rain event in the central-east zone, extending to the Stevens and Snoqualmie Pass areas. This layer is not present in the northeast from Washington Pass to Holden.

Snowdepth still decreases substantially east of the Cascade crest. In many areas below treeline, there has not been enough snow to present an avalanche danger.

Observations

North

North Cascades Heli was in the field Saturday and observed thin wind slabs, 8 inches thick on lee slopes. Roller balls were reported on sunny slopes in the afternoon, but natural loose wet avalanche was not observed.

Guides from both North Cascades Mountain Guides and North Cascades Heli were in the field Friday. Observations suggest storm snow weaknesses are gaining strength.

Central

Mission Ridge Pro Patrol Friday reported upside-down new storm snow. Avalanches observed failed within the storm snow.

Older but still relevant observations:

Several observations from the Mission Ridge and Blewett Pass areas have reported 2-3mm facets on the ground, including a recent post found here. This layer will need to be monitored. It could develop into a potentially dangerous weak layer in the future.

South

No recent 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.