Avalanche Forecast
Regions: Cascades - North West.
You can still trigger Wind Slab avalanches near the Mt Baker backcountry. Steer around recent drifts and deeper pillows of snow on steep wind exposed slopes. If you find yourself in terrain with dry, soft surface snow, take time to carefully evaluate layers in the top 1-2 feet of the snowpack. Use caution on steep, firm slopes where stopping a fall may be difficult and could have serious consequences.
Detailed Forecast
You can still trigger Wind Slabs at upper elevations near Mt Baker and the West North zone. Moderate Danger will be maintained as small Wind Slabs build late in the day on Sunday. Fresh Wind Slab may form immediately on the leeward side of terrain features and ridges near and above treeline. Steer around freshly drifted slabs to avoid triggering avalanches today.
Slick, frozen snow surfaces is one of the days hazards. A fall on steep, firm slopes could be difficult to stop and could have serious consequences. With cool temperatures, you can expect an end to wet avalanche problems, for now. There are some lingering layers in the top two feet of the snowpack. This includes surface hoar on shaded northwest through northeast aspects and a number of crusts on sun exposed slopes. Digging below the surface and using snowpack tests can help you gain information about these layers. Old, weak snow layers exist 5-6 feet below the surface. It's been weeks since any reported avalanches involved these deeper weak layers
Snowpack Discussion
The next storm is moving in with colder temperatures. Expect light to moderate snow and wind into Monday. Many slopes are capped with crusts between 6 inches and 2 feet thick at the snow surface.
At higher elevations dry soft snow can still be found. Moderate winds formed slabs as recently as Wednesday near and above treeline. A thin layer of surface hoar is buried about 1 foot below the surface under these slabs on north through east aspects. While you can still trigger these avalanches near Mt Baker, they are difficult to trigger in other zones.
Several avalanches 3/24-3/27 in the Crystal and Stevens areas failed on a similar layer of weak older snow buried on 3/22. Observations this week demonstrate this layer has been gaining strength. In some locations you may find a layer of small sugary facets above a firm melt-freeze crust. This layer has generally been reported 12-20†(30-50cm) below the snow surface and may be most prevalent above 5,500ft.
The much older 2/8 melt-freeze layer can still be found over 6 feet (120-200cm) deep in the snowpack. While this layer isn't listed in our current avalanche problem set, it may reawaken if it becomes wet.
Observations
North
On Friday, NWAC Observers Lee Lazara and Simon Trautman traveled in the Bagley Lakes area. They reported 3 triggered or natural avalanches about 1 foot deep on north aspects near treeline on slopes with recently drifted snow. The observers found a thin weak layer buried 3/25 at the interface of concern.
On Wednesday Mt Baker Ski Patrol reported 8-12 inches (20-30cm) of soft snow over a recent melt-freeze crust. This snow was very rapidly effected by small sun breaks and thinning in the clouds. Winds earlier in the weak formed new wind slabs at higher elevations.
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1