Snowfall amounts could vary throughout the region on Tuesday. Regardless, expect touchy fresh slabs to develop. The size and likelihood will be greater where there is more than 20 cm of new snow with wind.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Tuesday: Periods of snow 5-10 cm. The freezing level is near 1400 m and winds are moderate to strong from the SW. Wednesday: Another 5-10 cm of snow should accumulate before tapering off throughout the day. The freezing level is near 1400-1600 m and ridge winds ease from moderate westerly to light. Thursday: Cloudy with flurries. The freezing level remains near 1400-1600 m and wind increase to moderate from the SW.
Avalanche Summary
No new avalanches were observed on Sunday. You will likely find fresh touchy wind slabs in lee and cross-loaded terrain. These wind slabs should increase in size and likelihood throughout the week with continued light snow and moderate ridge winds. Late last week there were a couple reports of failing cornices triggering persistent slabs up to 60 cm deep on slopes below.
Snowpack Summary
5-15 cm of new snow overlies a melt-freeze crust on solar aspects and lower elevation terrain, and might be covering a layer of surface hoar on shady and sheltered slopes at treeline and in the alpine. Fresh wind slabs are likely in exposed lee and cross-loaded terrain. The surface hoar and/or crust layer buried in mid-February is now down 40-70cm. This layer was less reactive over the weekend with cooler temperatures. Large weak cornices remain concerning and have recently triggered persistent slabs on slopes below. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on this layer has become unlikely but it still has isolated potential to produce very large avalanches with a heavy trigger. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.
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.