Avalanche Forecast
Regions: Olympics.
An overnight refreeze will limit but not eliminate avalanche hazards Sunday. A lingering wind slab was triggered by a backcountry traveler Saturday reminds us that slab avalanches are still possible near and above treeline. Identify and avoid locations where avalanches are likely to trigger, such as convex rolls and near rocks.
Detailed Forecast
Clear skies Saturday night should allow for snow surfaces to refreeze. Surface crusts will delay but not remove avalanche hazard on Sunday.
Near and above treeline lingering wind slabs can still be found. The recent skier triggered avalanche is a reminder that slab avalanches are still possible. The upper snowpack is gaining strength, but this takes time. Identify and avoid areas in the terrain where avalanches are more likely to be triggered such as convex rolls, below cliffs, and shallow spots within the snowpack.
Warm air temperatures and mostly sunny skies will break down the new surface crust Sunday. This will take time and limit loose wet avalanche activity. Monitor changes in surface snow conditions. It only takes a few inches of wet surface snow to avalanche.
Despite the recent snow, early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
Light rain at Hurricane Ridge tapered off Saturday morning giving way to clearing skies and warm temperatures. Moist to wet surface snow developed near and below treeline. Clear skies Saturday night should allow surface snow to refreeze creating a new surface crust on most slopes.
Ridge top winds Thursday through early Saturday morning formed wind slabs on a variety of aspects.
About of foot of recent snow is bonding to the most recent rain crust. Below this rain crust, no notable layers of concern have been identified within the snowpack.
The height of snow across the terrain is quite variable with little snow in many areas below treeline. Numerous obstacles still exist at all elevations.
Observations
NPS rangers reported a skier triggered avalanche from the Hurricane Ridge area Saturday morning. The avalanche occurred as the skier was traversing across a steep convex rollover locally known as Avalanche Run near Poma Bowl (SW aspect around 5300 feet). The avalanche was estimated to be 12 inches deep, about 100 feet wide, and ran down slope for 300-400 feet. The skier was caught and carried but did not sustain any injuries.
Skier triggered wet snow avalanche 1/13, releasing on traverse (upper right). photo: NPS ranger
A separate natural, loose-wet avalanche occurred on Saturday in a known avalanche path named 20th of June. The avalanche occurred around 10am and ran for 300-400’.
Rangers also noted several glide cracks on steep smooth rock slabs.
NWAC pro-observer, Matt Schonwald was at Hurricane Ridge on Thursday 1/11. Matt found despite the significant storm snow, below the treeline elevation band had quite variable snow cover. Winds actively transported new snow near and especially above treeline, but the loading pattern was variable.
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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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