Warm temperatures and sunny skies forecast for the next few days will have a significant weakening effect on the snowpack. If solar radiation is particularly strong the avalanche danger could rise to HIGH.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Saturday
Weather Forecast
A ridge of high pressure will continue to dominate the region bringing dry conditions and mainly clear skies for the foreseeable future. Winds should be light to moderate from the west on Saturday, becoming northwesterly on Sunday and Monday. An inversion is expected for Saturday bringing valley cloud and alpine temperatures reaching +5.0. General cooling is expected for Sunday and Monday.
Avalanche Summary
No new avalanches were reported on Thursday; however, with current warming there is a high likelihood of loose wet avalanche activity with serious potential to re-activate deep persistent weaknesses.
Snowpack Summary
Snowpack depths vary, but in general there is now 200 to 250cm of snow at tree line and as much as 300 cm in select places in the alpine. In some areas we're still dealing with a relatively thin snowpack thanks to a windy early season and strong winds scouring slopes during recent storms. Roughly 100cm of snow fell last week and has been blown into stiff wind slabs in many areas. Below the recently formed storm slab you may find soft facetted snow and/or surface hoar buried around January 8th. This layer may coexist with a crust at lower elevations. Surface hoar layers buried in November and early December may still be found in the mid to lower snowpack, but are generally considered to be unlikely to trigger.A basal facet/crust combo (weak sugary snow above and below a crust) near the ground is still a concern in some areas and was likely the culprit with some of the very large avalanches reported in the wake of last week's storm..
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Loose Wet
Loose Wet avalanches are the 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. 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.
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.