Avalanche Forecast
Regions: Olympics.
Dangerous avalanche conditions should develop on Friday. Look for new wind slab near and above treeline. New snow may bond poorly to weak surface snow below treeline and become reactive by the end of Friday with increased loading and a gradual warming trend. Keep it conservative and expect increasing instability Friday.
Detailed Forecast
Will we reach a tipping point on Friday with widespread sensitive slab development or will recent weak layers be buried and await the next storm to become active?  A first round of light snow Thursday night followed by increasing shower activity and a gradual warming trend Friday should lead to an increasingly sensitive snowpack.
Dangerous avalanche conditions should develop on Friday. Look for new wind slab near and above treeline on non-traditional lee westerly aspects. Also, new snow may bond poorly to weak surface snow and become reactive by the end of Friday with increased loading and a gradual warming trend. The near-treeline band should be the trickiest to navigate where shallow new wind slab may have already buried recent weak surface snow.Â
In steep sheltered terrain continue to watch for small loose dry avalanches near terrain traps like cliff bands where even small avalanches can have big consequences. Â
With deep unconsolidated snow in many wind protected areas, there is an increased risk for tree well and snow immersion suffocation at this time. Ride or ski with a partner and keep them in sight at all times!
Even though the lower part of the below treeline band is filling in, watch for early season travel hazards such as barely covered rocks and open creeks.
Snowpack Discussion
Weather and Snowpack
An active and cool weather pattern has resulted in a snowy December thus far with the Hurricane Ridge NWAC station recording about 3 feet of snow.
Cold and fair weather has taken hold since Monday. There have been many reports of right side up, favorable density profiles with lower density snow nearer the surface in the Cascades and we expect similar conditions in the Olympics.
Given the favorable snowpack profile, good bonds between older snow layers and a lack of deeper layer concerns, avalanche problems should be confined to the upcoming old snow/new snow interface or within new storm layering.Â
In areas near and below treeline not affected by moderate easterly winds over the last 24 hours, near surface faceting and/or surface hoar should be widespread.Â
Recent Observations
Recent moderate easterly winds have likely built new wind slabs on lee aspects near and below treeline in the Hurricane Ridge area with plenty of low density of snow available for transport.Â
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: North, South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
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: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Loose Dry
Release of dry unconsolidated snow. These avalanches typically occur within layers of soft snow near the surface of the snowpack. Loose Dry avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs. Loose Dry avalanches can trigger slab avalanches that break into deeper snow layers.
Loose Dry avalanches are usually relatively harmless to people. They can be hazardous if you are caught and carried into or over a terrain trap (e.g. gully, rocks, dense timber, cliff, crevasse) or down a long slope. Avoid traveling in or above terrain traps when Loose Dry avalanches are likely.
Loose Dry avalanche with the characteristic point initiation and fan shape.
Loose dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1