New snow and forecast strong southwest winds will continue to build reactive storm slabs. Moist and wet surface snow will weaken with warmer temperatures and rain at lower elevations.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Up to 10 cm expected overnight on Tuesday. New snow 5-10 cm on Wednesday. Ridgetop wind strong from the southwest and freezing levels rising to 1500 m. Thursday: Mix of sun and cloud. New snow up to 5 cm. Ridgetop wind strong from the southwest and freezing levels 1300 m. Friday: Yet another blast of winter up high! Heavy snow, 30-40 cm expected. Ridgetop winds strong-extreme from the southwest with freezing levels near 1400 m.
Avalanche Summary
Several, natural storm slabs up to size 2 and loose wet avalanche activity from steep solar aspects were observed on Monday. Cornice control also produced size 2's but not pulling slabs from the slopes below. Avalanche activity will be on the rise with the incoming storm. Its still winter out there!
Snowpack Summary
Warm temperatures and rain have moistened the snow surface on all aspects and at all elevations with new snow accumulations in the alpine up to 15 cm on Tuesday. Reactive storm slabs and wind slabs are building with continued snow and strong southwest winds. Ridgelines are heavily corniced and could act as a trigger on the slope below. A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 120 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.Below this, the snowpack is well-settled and strong.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.