Cautious route-finding and conservative decision making are essential. Wind slabs may dig deeper and fail on the persistent weak layer below.
Confidence
Poor - Wind effect is extremely variable on Saturday
Weather Forecast
Synopisis: On Saturday, the low off the North Coast will have weakened sufficiently, however unsettled conditions will exist with cloudy skies and light snow. Ridgetop winds will be moderate from the northwest. The next low pressure system will affect the Interior late Sunday afternoon and persist through Tuesday. However; models show the arctic air invading the South Rockies and Lizard Range before then, which will send temperatures plummeting and likely keep the moist air out. Snow amounts will be light 5-10 cm overnight Sunday and into Monday. Ridgetop winds will be strong from the northwest and treeline temperatures will hover near -15. Freezing levels will be at valley bottom through Monday, then rising Tuesday
Avalanche Summary
No new avalanches have been reported.
Snowpack Summary
Snow surfaces are variable with northerly, wind exposed aspects showing firm wind press or scoured exposed crust, and more sheltered locations have up to 30 cm of low density, faceted snow. In the alpine and at treeline, strong northerly winds have transported this snow into stiff and reactive wind slabs on opposite slopes. Up to 70 cm below the surface you will likely find a hard, thick crust which formed mid-December. At higher elevations this crust has facets (sugary) snow above it and well-preserved surface hoar up to 10 mm in size in sheltered locations at treeline and below. Where the crust exists, it may be bridging triggers from penetrating to deeper persistent weaknesses. However, on high alpine slopes above where the rain crust formed, or in areas where rain didn't occur, deeply buried facets may still be susceptible to triggering, especially in thinner snowpack areas.
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.
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.