Avalanche Forecast
Regions: Olympics.
A peak in the avalanche danger should be seen Tuesday morning. You may encounter a greatly increasing avalanche danger with elevation on Tuesday. Avoid travel in terrain connected to higher start zones.
Detailed Forecast
Increasing strong southwest flow aloft will carry a major deepening low pressure system and cold front across the Northwest on Monday and Tuesday. The exact track of the low is hard to predict and will make a big difference for local weather. At Hurricane expect moderate to strong shifting alpine winds Monday night and Tuesday, about 5-10 inches of new snow by Tuesday early morning, and more new snow mainly through Tuesday late morning.
 New storm slab is likely to form Monday night and Tuesday morning in areas with rapidly accumulating new snow. This should be seen from the upper part of the near treeline up to the limited above treeline terrain at Hurricane.
New wind slab will form on lee slopes mainly near and above treeline Monday night and Tuesday morning. This is most likely on northwest to southeast aspects but is possible on other aspects. Watch for firmer wind transported snow.
 A peak in the avalanche danger should be seen Tuesday morning. You may encounter a greatly increasing avalanche danger with elevation on Tuesday. Avoid travel in terrain connected to higher start zones.
The recent warm 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
A series of mild storm systems left the Hurricane Ridge area with dust on crust Saturday morning and again on Sunday morning. A approaching stronger system with moist west flow then brought 3.5 inches of snow on Monday morning.
The high pressure system that was in place from December 3 through December 14 created a variety of snow surfaces. But light rain at Hurricane Ridge on Friday should have destroyed weak surface hoar or near surface facets from that period that may have persisted on northerly aspects.Â
The sunny weather prior to the recent storm revealed vastly more snow free areas, especially on solar aspects and anywhere near ridgelines. The most consistent snowpack remains 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
Observations
No human-triggered avalanches have been reported in well over a week.
The Hurricane ranger on Monday morning reported no avalanche activity, with a snow line of about 4500 feet.
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!
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: All elevations.
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, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1