Avalanche Forecast
Regions: Olympics.
Rising snow levels on Tuesday will produce small Loose Wet avalanches near and below treeline. Watch for warning signs like new roller balls, pinwheels, and natural Loose Wet avalanches as temperatures rise and light snow turns to rain near and below treeline. Shallow new Wind Slabs will form mainly above treeline Tuesday as increasing winds transport new and recent snowfall onto lee slopes at higher elevations.
Detailed Forecast
Rising snow levels on Tuesday will produce small Loose Wet avalanches near and below treeline. Watch for warning signs like new roller balls, pinwheels, and natural Loose Wet avalanches as temperatures rise and light snow turns to rain near and below treeline. Even small Loose Wet avalanches may carry you into terrain with high consequences such as over cliffs or into gullies. Avoid slopes where loose wet avalanches may become large by entraining deeper amounts of recent snowfall.
Shallow new Wind Slabs will form mainly above treeline Tuesday as increasing winds transport new and recent snowfall onto lee slopes at higher elevations. You may be able to trigger a Wind Slab avalanche at upper elevations on steep slopes near ridge tops or in cross-loaded terrain features. Watch for clues like variable snow height, drifts, cornices, and stiff snow that produces cracking. These are all indicators that you could trigger a Wind Slab. You can avoid triggering these avalanches by steering around steep roll-overs, unsupported features, and obvious start zones where you suspect Wind Slabs.
Snowpack Discussion
Cloudy skies, intermittent snowfall and slowly rising snow levels summed up the weather at Hurricane Ridge Monday. Several inches of snowpack settlement have occurred since the last snowfall.Â
A skier triggered a Wind Slab avalanche late in the day Friday or early Saturday morning. These Wind Slabs were formed by moderate to strong southerly winds redistributing 10" of new snow that fell Thursday through Friday. Wind slabs were found on northerly aspects near and above treeline and stripped snow off of exposed southerly aspects.
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
On Saturday, NPS rangers reported a small skier-triggered wind slab (40 ft wide, running 80 ft) wide on a north-facing aspect. North-facing aspects preserved soft snow.
Chalky-textured wind-loaded pillow near ridge-line adjacent to the skier-triggered wind slab. Photo credit: Sarah Crosier, Hurricane Ridge NPS
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€Â (15-20cm), but were observed up to 1 foot (30cm) thick. Exposed windward slopes were often stripped of the new snow down to a firm and hardening crust.
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.
Elevations: Treeline, Below Treeline.
Likelihood: Likely
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1