Avalanche Forecast
Regions: Olympics.
Lingering wind slab on lee slopes near and above treeline may be tougher to trigger, but still possible on Sunday. Wet loose avalanche potential will vary considerably by how the weather forecast plays out. Moderate avalanche danger means heightened avalanche conditions (hazard) on specific terrain features, so match your terrain selection to the avalanche problems.
Detailed Forecast
A warm front lifting north across the area should bring light rain and clouds to the Olympics Sunday. A warming trend will begin Sunday, but will likely be tempered by breezy winds near and above treeline and extensive cloud cover. However, there is a decent amount of uncertainty for Sunday's forecast. Â
Lingering wind slab on lee slopes in the near and above treeline elevation bands may be tougher to trigger, but still possible Sunday. Watch for signs of snowpack cracking and firmer wind transported snow on lee slopes.
Wet loose avalanche potential will vary considerably by how the weather forecast plays out Sunday. Light rain will encourage natural wet loose activity on steeper slopes. Be aware of loose wet avalanche potential above terrain traps (like above cliffs or near gullies), where even small wet avalanches can become powerful and have unintended consequences. Â
Snowpack Discussion
The last heavy rain fell in the Olympics January 27th-28th with over 2 inches of rain recorded at the NWAC station at Hurricane Ridge.
A strong occluded front with strong winds crossed the Northwest January 29-30th. Hurricane Ridge had about 14 inches snowfall.
NWAC pro-observer, Matt Schonwald visited Hurricane January 29th and found rapidly building wind slab and extensive loading on lee slopes in all 3 elevation bands. New cornices were sensitive to triggering but still relatively small.Â
Cool, benign weather followed Sunday through Tuesday. A sun crust formed on many solar slopes and surface hoar was seen on many non-solar slopes in the Cascades so this is possible in the Olympics as well.
A cold front and then a warm front crossed the Northwest on Wednesday and Thursday. The Hurricane ranger reported about 8 inches of snowfall for the 2 days ending Friday morning. No snowpack observations were received Friday due to the closed road.Â
An additional 7 inches of snow fell with a cooling trend during Friday night's fast, yet powerful front. Lee slopes were likely loaded by strong S-SW winds with this system.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, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Possible
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1