Avalanche Forecast
Regions: Olympics.
Watch for loose wet avalanches as shallow natural loose avalanches will release on steep slopes of all aspects, particularly NW-SE aspects. Observe snow depths above the crusts and avoid terrain traps exposed to steeper terrain. Watch for early season terrain hazards, rocks, creeks etc.
Detailed Forecast
Sharp warming Sunday night and increasing west winds to 20-25 mph will accompany light incoming snow, which should change to light rain at all elevations in the hurricane ridge area by morning and continue throughout the day.Â
The recent rain-shadowing in Friday's storm and again on Sunday should help limit our avalanche danger in this zone, with limited snow to move above a well-consolidated base.
Shallow and small and shallow atural loose wet avalanches avalanches are the primary concern. They will release on steep slopes of all aspects. The Hurricane ridge area is not expected to see small snow totals, so expect the potential for loose wet avalanches to entrain more snow in areas where wind transports more snow on Saturday night (NW-SE aspects). Be especially careful of loose wet avalanches around terrain traps.Â
Due to the rising freezing levels, wind and storm slab are not anticipated to be problems here during the daylight hours, Sunday. However, gradual cooling temperatures Sunday night into Monday may create shallow storm or wind slab concerns for Monday.Â
The recent warm, sunny weather has melted much of the early season snowpack and exposed terrain hazards. Expect terrain hazards with poorly covered rocks, vegetation and creeks, particularly on south-facing terrain, at lower elevations, and on exposed ridges where wind events have stripped much of the seasons snowcover.
Snowpack Discussion
The first in a series of storm systems left the Hurricane Ridge area with dust on crust. The high pressure system that was in place from December 3 through December 14 created a variety of snow surfaces. However, light rain fell at Hurricane Ridge on Friday before temperatures cooled and re-froze the snowpack. The main effect of the light rain was to destroy any remaining weak surface hoar or near surface facets that may have persisted on northerly aspects. A half inch of snow fell Friday afternoon and was reported by the NPS as of Saturday morning on the re-frozen old snow interface, creating dust on top of a rain crust.
At Hurricane Ridge, the warm and sunny weather from December 3-14 created a melt-freeze crust which should sit directly underneath the thin rain crust on solar aspects and result in a thicker, more supportable crust on solar aspects. The sunny weather prior to our recent storm revealed vastly more snow free areas, especially on solar aspects and anywhere near ridgelines. At the end of this cycle, the most consistent snowpack remained on shaded northerly aspects below any ridgelines where the snowpack height averages about 3-4 feet.
Below the upper dust on crust lies stable and settled old snow which sits over the strong Thanksgiving crust about 1 foot below the surface.Â
No human-triggered avalanches have been reported in well over a week.Â
Observations
NWAC Professional Observer Matt Schonwald was in the Hurricane Ridge area on Friday, December 15th. The big takeaway is the dramatic difference the snowpack has undergone over the past 12 days of high pressure, sunshine and very mild temperatures. The average height of snow on shaded slopes near treeline away from ridges is consistently between 3-4 feet deep. There were no avalanche concerns in the overall strong snowpack, where it remained!
Surface crusts dominated the conditions with many sun and wind exposed terrain void of snow.
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: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1