Avalanche Forecast
Regions: Olympics.
Wind driven snow will build fresh winds slabs Monday night and Tuesday. Watch for evidence of wind-transported snow including active transport or wind-stiffened snow. Avoid steep, wind-loaded terrain or terrain where a small slide might be consequential near cliffs or other terrain traps.
Detailed Forecast
Rapid cooling Monday late afternoon and early evening should begin to refreeze the upper snowpack, forming a new crust. Moderate W-SW flow and light additional snow should accumulate at all elevations Monday night and Tuesday with 2-6" of relatively low density new snow anticipated on top of the crust.Â
The refreezing upper snowpack should generally put to rest some of the deeper slab avalanche concerns we've been having in recent days.
While snowfall intensities are not expected to be sufficient to develop a storm slab problem, consistent W-SW winds will continue to transport low density snow on the refreezing snow surface.Â
Small wind slabs will form Monday night and Tuesday, and will be possible to trigger near and above treeline. They will run slightly farther and will be easier to trigger later in the day on Tuesday as the bed surface becomes increasingly firm and the wind slabs gain size. Due to the strength of the winds and earlier transition to snow, expect touchier and larger wind slabs above treeline. Reduce your risk of triggering a wind slab by watching for wind-stiffened snow near ridge-lines or evidence of active transport onto lee slopes. Keep in mind that even a small avalanche can be dangerous if you are caught above a cliff or another terrain trap.
Snowpack Discussion
A warm and wet system brought 1.15" of water to Hurricane Ridge since 4 AM on Monday. This has likely saturated the upper snow pack, which has seen 15" of consolidation in the past 2.5 days. Wet snow surface conditions exist due to the recent rainfall to the top of Hurricane Ridge terrain.
Prior to the recent storm snow settlement, a cool, stormy period that started January 16th ended with Saturday's system brought warming towards the midday. Warm air temperatures, additional snow, and strong southerly winds formed deep wind slabs on lee slopes. During the storm cycle, winds redistributed significant snow forming variable snow depths and scour crusts.
Observations
No observations were received Sunday as the road remained closed due to the elevated threat of large avalanches.Â
NPS rangers reported several natural avalanches Saturday, several that deposited debris onto the Hurricane Ridge road.Â
On Friday, Jan 26th, pro-observer Matt Schonwald reported on the tremendous change in the snowpack since this storm cycle began. Southerly winds plus nearly continuous snowfall sculpted the landscape near and above treeline. Large and very easy to trigger cornices, deep wind rolls and huge snow depth variations were observed. Snow depth on a south aspect at 5000' measured 120 cm vs. 370 cm at the same elevation on a northerly lee aspect.
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: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1