In some areas, wind slabs are still reactive to the weight of skiers and riders. Make observations continually as you travel.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Expect mainly a mix of sun and cloud for the forecast period, although clear skies may develop for Christmas day. Ridgetop winds should remain mainly light. Alpine temperatures should measure about -15 on Thursday, and then drop to about -20 on Friday and Saturday.
Avalanche Summary
Evidence of a few natural wind slab avalanches to size 2 was observed in lee alpine terrain on Monday and Tuesday. The avalanches occurred in response to new snow and wind on the weekend. On Wednesday morning in the Golden backcountry, a size 2 skier-triggered wind slab avalanche occurred on a northwest aspect at about 2400m. It was up to 50cm in depth and ran approximately 600m.
Snowpack Summary
Throughout last weekend there was up to 20cm of new snow. Strong southwesterly winds have redistributed much of this snow into wind slabs in exposed lee features in the alpine and at treeline. With the current cold weather, I'd suspect continued faceting in the snowpack. Areas most affected would include windward or cross-loaded rocky areas at higher elevations. Between 40 and 80cm below the surface you'll likely find a layer of weak buried surface hoar which is most prominent between 1400m and 1800m although it may extend to higher elevations in some parts of the region. Snow pit tests suggest that human triggering of this interface is becoming unlikely, although a release at this interface could be destructive in nature.
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.