Avalanche Forecast
Regions: Olympics.
New wind slabs will slowly gain strength Saturday. You are most likely to trigger a wind slab on convex rollovers, steep unsupported slopes, and below fresh cornices. Use visual clues such as snow drifts, cornices, and frim snow with cracking to identify and avoid wind loaded areas. If the sun comes out, be ready to get off of and avoid steep sunny slopes where you see new rollerballs and pinwheels.
Detailed Forecast
Avalanche danger will continue to slowly decrease Saturday as newly formed wind slabs begin to gain strength. Even though the avalanche danger is decreasing, you may still trigger a wind slab on steep slopes near ridgeline. You are more likely to trigger a wind slab on convex rollovers, steep unsupported slopes, or below fresh cornices. You can use visual clues to identify and avoid wind loaded slopes greater than 35 degrees. Snow drifts, cornices, and firm snow surfaces with cracking all indicate that nearby slopes received wind deposited snow.
The strong March sun can quickly change conditions on slopes receiving direct sunshine. If the sun comes out, expect small loose wet avalanches, rollerballs, and pinwheels. Move off of and avoid steep sunny slopes during periods of intense sunshine.
Snowpack Discussion
Around 10 inches of new snow has accumulated in the Hurricane Ridge area as of Friday afternoon. Moderate to strong southerly winds redistributed the new snow forming wind slabs on northerly aspects near and above treeline and stripping snow off of exposed southerly aspects.
In sheltered areas generally loose surface conditions exist. This resulted in three small loose dry avalanches Thursday.
The new snow sits on a variety of old snow surfaces. On slopes that received direct sun during the recent clear weather, a firm and thick melt-freeze crust can be found. On shaded slopes a thinner more breakable crust has been observed.
Weaker layers of sugary facets and thin crusts have been found within the snowpack. Current observations suggest that these weak layers are not widespread. You are most likely to find older weak snow on East facing slopes about 1 ft (30cm) below the snow surface.
There are no other significant layers of concern in the snowpack at this time.
Observations
NWAC observer and NPS rangers on Thursday, 3/22 found blowing snow actively building fresh cornices and wind slabs above 5000’. Slabs were generally shallow (6-8â€, 15-20cm) but were observed upto 1 foot (30cm) thick. Exposed windward slopes were often stripped of the new snow down to a firm and hardening crust.
Avalanche Problems
Wind Slabs
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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1