Avalanche Forecast
Regions: Olympics.
Careful snow pack evaluation and caution will be necessary at Hurricane Ridge on Tuesday.
Detailed Forecast
Three day snowfall ending Tuesday morning should be about a foot at Hurricane Ridge. West southwest flow aloft should continue to carry warm front moisture to the Northwest. This should cause rain or snow showers with rising snow levels at Hurricane Ridge.
Wind slab will be a likely concern mainly on lee slopes at higher elevations. This should be mainly north to southeast aspects. Watch for signs of firmer wind transported snow.
Storm slab should also remain likely above the snow line on Tuesday on a wider variety of aspects. Wetter denser new snow accumulating over lower density snow will contribute to this concern.
Below the snow line wet loose avalanches will be the primary concern. Steep slopes that received heavy snowfall and then receive rain will be primed for wet-loose avalanches. Natural snowballing and smaller natural releases are usually precursors to this type of avalanche.
Snowpack Discussion
Recent Northwest Weather
A 2 week storm cycle ended a week ago causing about 9 feet of snowfall and avalanches at Hurricane Ridge.
Warm dry weather was seen late last week Wednesday to Saturday causing wet snow avalanches and melt/freeze crusts at Hurricane Ridge and throughout the region.
Observations for Hurricane Ridge area
NWAC observer Tyler Reid at Klahhane Ridge on Friday found plenty of wet unconsolidated snow on solar aspects below tree line. Some small surface hoar growth was noted in places. Here is his video from Friday.
On Saturday, a ranger and Tyler reported a very hard surface crust had formed as a result of the significantly colder overnight and early morning temperatures.
Another storm cycle began on Sunday and an avalanche cycle was likely at Hurricane Ridge as in the Cascades Sunday night and Monday morning although there are no observations to confirm at Hurricane Ridge. Poor bonds to the melf-freeze crust from late last week will likely have provided bed surfaces.
The mid and base pack around Hurricane Ridge still consists of stable crusts and melt form layers from periods of warm weather earlier this winter. But below tree-line zone on solar aspects rain and mild temperatures may keep the shallow snowpack wet and unconsolidated.Â
Avalanche Problems
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine, 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: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Likely
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.
Elevations: Below Treeline.
Likelihood: Likely
Expected Size: 1 - 1