The wet, warm, and windy storm will result in High avalanche danger.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Warm, wet, and windy overnight as another 20-30 mm of precipitation moves into the region. The freezing level is expected to be about 2500 metres overnight and then rise up close to 3000 metres on Saturday. Another 10-15 mm during the day on Saturday with strong Southwest winds, and then another 5-10 mm by Sunday morning. On Sunday the freezing level may start to creep down a bit in the alpine, but still very warm in the valleys. Forecast precipitation for Sunday and Monday are starting to look a bit lower, with 5-7 mm expected on Sunday and 7-10 mm for Monday. Freezing level should remain close to 2400 metres on both days.
Avalanche Summary
Recent avalanche activity progressed from a limited avalanche cycle on Saturday and Sunday (mainly from wind loaded terrain), to several explosive and rider triggered avalanches up to size 2 on Monday and Tuesday. Conditions will start to change heading into the weekend. Warm temperatures and rain is expected to tip off another round of wet avalanche activity on Friday.
Snowpack Summary
Stormy weather is forecast to continue and add to the 50 cm of settled storm snow that sits on a hard crust and/or surface hoar layer. Previous strong W-SW winds redistributed snow in exposed terrain creating deep and dense wind slabs in lee features. The new snow seems to be bonding well to the crust, which is most pronounced between about 1500 m and 2200 m. The distribution of the surface hoar seems spotty across the region, but some operators found it to be widespread in their tenure before it was buried. Deeper snowpack weaknesses have become unreactive, but a recent snow profile highlights the stark hardness contrast between a deep persistent weakness and the surrounding snow. Scenarios like this with deeply buried soft snow surrounded by hard snow aren't confidence inspiring because it all hinges on the strength of the overlying slab, which is often volatile and susceptible to significant warming and loading. Especially with very heavy triggers (like a cornice fall) in the wrong spot (like a thin snowpack area).
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.