Avalanche Forecast
Regions: Olympics.
With high freezing levels and generally light winds Thursday, loose wet avalanches should be again be the primary avalanche concern on solar slopes in the Olympics.
Detailed Forecast
With high freezing levels and generally light winds Thursday, loose wet avalanches again should be the primary avalanche problem on solar slopes in the Olympics.
Temperatures should be even warmer Thursday, so watch for pinwheeling and rollerballing as precursors to more significant loose wet activity and especially be wary of loose wet avalanches around terrain traps, such as slopes that would funnel wet snow like gulleys or depressions, also slopes above cliff bands or dense trees.Â
Older wind slab may still be sensitive in isolated terrain features near and above treeline.Â
Snowpack Discussion
Weather and Snowpack
Last week, heavy rain and mild temperatures dominated along the west slopes and the Olympics, forming the latest rain crust. There were about 1.5 inches of rain at Hurricane over the 2 days ending Tuesday morning, February 16th.
An active and at times cooler and stormy pattern began to bury the crust on February 17th and deposited about a foot of snow at Hurricane from Wednesday through Saturday morning. A few additional inches of snow fell from Sunday through Monday morning.
High pressure over the past few days has brought warm temperatures, with periods of sun and clouds along with light SE winds.Â
The mid and lower snow pack in the Olympics should be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
Professional NWAC observer, Matt Schonwald was at Hurricane Ridge on Friday. Recent storm snow deposits of about 4-6 inches had accumulated in wind sheltered locations. Very strong southerly winds were building shallow wind slabs on lee slopes near tree line below ridges and also building small cornices.
A small wind slab was triggered on a lee slope called Sunrise Slope on Saturday although details are not available.
By Wednesday afternoon of this week, daytime temperatures climbed into the mid 40's at Hurricane, allowing for settling wind slabs and causing surface snow melt, especially on solar aspects.
Avalanche Problems
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1
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, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1