Destructive persistent weak layers should still be on your radar if you're heading to the north of the region.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Tuesday: A mix of sun and cloud. The freezing level remains near 500-600 m and winds are light and variable. Wednesday: Periods of snow – 5 cm. The freezing level is around 800 m and winds are moderate from the SW-SE. Thursday: Cloudy with light snow. The freezing level is near 1000 m. Ridge winds are moderate from the SW.
Avalanche Summary
On Sunday, there was a report of a size 2 wind slab avalanche that was remotely triggered by a skier in the mountains north of Pemberton. It was triggered from a thin snowpack area and released on a steep cross-loaded slope about 50 m away. Nearby, a cornice fall also triggered a size 1.5 slab on the wind-loaded slope below. There were no new reports of avalanches from the southern part of the region on Sunday.
Snowpack Summary
In the south, 40-70 cm of recent storm snow sits on a widespread and generally supportive rain crust that was buried on Jan. 28. The bond to the crust appears to be fairly good but at least one notable storm snow weakness was observed 10 cm above the crust. Fresh pockets of wind slab may also form in immediate lee features. The combination of heavy storm loading, rain, and warm temperatures likely flushed out the mid-January persistent weakness in most areas in the Cascades. Further north, generally 20-40 cm of dry storm snow overlies the late-Jan rain crust below around 1800-2000 m. Above this elevation the new snow sits on settled storm snow or previously wind affected surfaces. Fresh pockets of wind slab are likely in exposed lee terrain. Where it still exists, the mid-January surface hoar layer is between 60 and 130 cm below the surface. This persistent weakness could be lingering on higher elevation slopes that did not previously avalanche and triggering remains a concern.
Problems
Wind Slabs
Wind Slab avalanches are the 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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.