Avalanche Forecast
Regions: Olympics.
Dangerous avalanche conditions are expected Sunday especially in the near and above tree line. Careful snow evaluation and conservative decision-making should be essential on Sunday.
Detailed Forecast
A stronger cold front will cross the Northwest on Sunday. Expect increasing strong alpine winds and significantly increasing moderate to heavy rain or snow on Sunday. New snow amounts of about 5-10 inches should be seen in the near and above tree line by the end of the daylight hours.
This weather should transport snow and build new wind slab on lee slopes through the day. This should be mainly on N to E slopes in the above and near tree line bands. Watch for firmer wind transported snow and surface snow cracking from the tips of your skis.
New storm slab should also build through the day in areas that rapidly accumulate snow. This avalanche problem may work its way down into the upper treeline by the end of the day. Rapid snow accumulation is generally more than an inch or 2 an hour for several or more hours.
Dangerous avalanche conditions are expected by Sunday afternoon especially in the near and above tree line. Careful snow evaluation and conservative decision-making should be essential on Sunday.
The problem of loose wet avalanches will be left off the problem list on Sunday but watch for signs of significant wet snow at the lowest elevations.
Snowpack Discussion
Weather and Snowpack
The last snowfall occurred late last week when about a foot of snow fell ending February 20th. Some cornices and wind slabs formed during this period but recent warm weather and sunshine have likely settled and stabilized wind slabs.
Springlike weather under high pressure Wednesday and Thursday caused abundant sunshine with temperatures climbing into the upper 40's Thursday afternoon. This weather has allowed for melt-freeze crust formation overnight and varying amounts of wet surface snow depending on slope aspect.
A weak front brought mostly light rain to Hurricane Friday night to Saturday morning.
Recent Observations
NWAC pro-observer Matt Schonwald was at Hurricane Ridge Friday and found mostly consolidated stable snow. N to E slopes had areas of 25-30 cm of wind transported 4F snow well bonded to 1F MF grains in the upper snow pack. South slopes were melted out in some places with shallower dense stable snow in others.
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, North East, East, South East.
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