Avalanche Forecast

Archived

Jan 18th, 2016–Jan 19th, 2016

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Even with an overall stabilizing trend on Tuesday, dangerous avalanche conditions may persist on lee wind-loaded slopes above treeline and where storm slabs remain possible for human triggering. Evaluate the snowpack carefully and identify terrain features of concern, such as convex rollovers and slopes that may have received recent wind deposited snow.

Detailed Forecast

A weak front should pass overnight Monday, followed by light showers tapering off Tuesday morning. Another frontal system is expected late Tuesday afternoon and night.

New, shallow wind slab should be found mainly on lee north to east slopes near and especially above treeline. Generally avoid wind loaded slopes above treeline.

Older storm slabs should have mostly settled and stabilized with some new storm slabs possible. Choose lower angled slopes if you find sensitive storm layers.

Snowpack Discussion

Deep storm snow that fell during mid-late December is well settled, homogeneous and has stabilized so the current avalanche danger should remain confined to the uppermost recent storm snow. Fair weather over the New Year caused extensive surface hoar that was buried by a light snowfall at Hurricane January 3rd. No avalanches have been reported on this persistent layer, and an active, mild pattern over the last two weeks has likely eliminated this layer in Hurricane Ridge area.

Avalanche concerns should be limited to mainly shallow recent storm snow. Strom snow is settling quickly based upon the observations made by Park Rangers at Hurricane.

The latest period of snowfall has deposited about 1 foot of snow over the past three days at Hurricane Ridge, with fluctuating snow levels and periods of strong, mostly S-SW winds.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.