New wind slabs are expected to develop on Sunday afternoon. The Avalanche Danger may increase throughout the day.
Confidence
Moderate - Timing of incoming weather systems is uncertain on Sunday
Weather Forecast
A series of weak systems will pass through the region over the forecast period. Expect 5-10cm of new snow on Sunday afternoon, a mix of sun and cloud on Monday and an additional 5-10cm of snow on Tuesday. Ridgetop winds will be extreme from the southwest on Sunday afternoon, strong and northwesterly on Monday, and strong and southwesterly on Tuesday. Freezing levels should hover around 1600m for the forecast period.
Avalanche Summary
On Friday several size 1.5 sluffs were observed in steep terrain. Depending on aspect and elevation, they either ran as loose wet or loose dry avalanches. A few size 1 wind slabs were also reported on mostly north facing alpine terrain. Increasing winds and light amounts of new snow will spark a new round of wind slab activity in higher elevation lee terrain.
Snowpack Summary
A supportive near surface crust is likely in most places aside from shaded aspects at treeline elevations, and lower elevations that are under melt-freeze conditions. This crust and perhaps new surface hoar (where it survived the heat, rain and sun) could be buried by as much as 15-20cm of fresh snow or deeper wind slabs. Avalanche professionals are still monitoring the persistent weakness buried early January, which is now down 80-120 cm. In most places it is no longer sensitive to light triggers. However, in specific locations it still produces hard, but sudden results in snowpack tests.
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.