Avalanche Forecast
Regions: Cascades - North West.
Wind slab may be found on lee slopes near and above treeline, potentially extending into the below treeline depending on the local rain/snow line Sunday night. Small loose wet avalanches will remain sensitive to human triggering on Monday and possible on any steep slope regardless of aspect near and below treeline. Even small avalanches may travel further than you expect due to the 1/5 crust providing a firm sliding surface, so avoid steep terrain exposed to terrain traps.
Detailed Forecast
There is more uncertainty in the Mt. Baker forecast regarding how much new snow and/or rain will occur Sunday night. A warming trend with light to occasionally moderate precipitation is forecast to occur through early Monday morning, followed by a drying and likely partial clearing trend late morning through the afternoon. Freezing levels will be on the mild side.Â
Wind slab may be found on lee slopes near and above treeline, potentially extending into the below treeline depending on the local rain/snow line Sunday night. Approach lee slopes with caution on Monday, watching for signs of recent or active wind transport. The Considerable rating has been added to the above treeline band due to the increased possibility of larger wind slabs recently formed at higher elevations.Â
A natural loose wet avalanche cycle should have occurred Sunday night in many elevations and areas. Loose wet avalanches will remain sensitive to human triggering on Monday. Loose wet slides should be small in size, but possible on any steep slope regardless of aspect near and below treeline.Â
Shallow storm slabs will be listed as an avalanche problem in the Mt. Baker zone but they should quickly become stubborn to triggering as the day progresses.Â
Small avalanches may travel further than you expect due to the 1/5 crust providing a firm sliding surface, so avoid steep terrain exposed to terrain traps.
Early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
On Sunday, light precipitation that began as light snow during the morning had mixed with light rain or freezing rain at lower elevations of Snoqualmie Pass and at Paradise on Mt. Rainier by late morning or early afternoon. Light snowfall accumulated at Mt. Baker and Stevens Pass through the afternoon. Winds were transporting new snow and building fresh but thin wind slab in the Mt. Baker area, near tree-line at Paradise in some near treeline areas of Snoqualmie Pass. Any new or recent snow overlies the 1/5 rain or freezing rain crust.Â
Below the 1/5 crust, reports indicate a strong upper snowpack with no notable layers of concern and a multitude of crusts formed over the last two weeks.Â
Observations
North
NWAC pro-observer Lee Lazzara was out in the Bagley Lakes area on Sunday. Lee found gusty winds transporting new and recent snow onto various aspects and forming thin but sensitive wind slab through the early afternoon well down into the below treeline band. The 1/5 rain crust was ski supportable. Visibility was poor but glide cracks had re-opened on some steep rock faces due to the heavy rain event that ended Friday.  No new avalanche activity was observed.Â
Central
NWAC professionals traveled in both the Snow Lake and Kendall Peak areas of Snoqualmie Pass on Sunday. Thin wind slab, up to 8" (20 cm), was building on a north aspect above Snow Lake at 4600 ft and reactive in column tests, failing on the 1/5 crust as of mid-day. In the Kendall area, 1-4" of snow was reported above the 1/5 crust. Little active snow transport was observed to ridgecrest. A thin rain or freezing rain surface crust was forming later in the day. No new avalanche activity was observed.  Â
NWAC pro-observer Jeremy Allyn was in the Smithbrook/Rainy Pass area east of Stevens Pass on Sunday. About 3-4" of recent and new snow was well bonded to the 1/5 crust which was semi-ski supportable. Travel conditions were difficult. No new avalanche activity was observed.Â
South
A professional in the Paradise area Sunday reported a switch form snow to freezing rain/ice pellets by late morning. This trend likely continued into Sunday afternoon as light to moderate precipitation produced no new snow at the Paradise weather station. As of mid-day Sunday, 4-6 inches of recent and new snow was well bonded to the 1/5 crust with a thin freezing rain crust noted at the surface. Some wind transport was occurring near treeline above 6000 feet due to moderate west winds. No new avalanche activity was observed.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: All aspects.
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: South East, South, South West.
Elevations: All elevations.
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: Possible
Expected Size: 1 - 1