Residual storm instabilities may still be a concern, especially in the alpine. Avoid steep unsupported slopes and wind-loaded features. If the sun comes out, use extra caution on south-facing slopes.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
A dirty ridge of high pressure should keep things mainly dry on Wednesday but light scattered flurries are possible. Mostly cloudy conditions are expected but sunny breaks are possible. Freezing levels are forecast to be around 1800m and alpine winds light-to-moderate from the SW. On Thursday, a mix of sun and cloud is expected with light scattered precipitation. Freezing levels are forecast to rise to over 2000m. On Friday, dry conditions are expected with a mix of sun and cloud. Freezing levels may peak on Friday at around 3000m.
Avalanche Summary
Widespread natural, human-triggered, and explosive controlled avalanches up to size 3 were reported on Friday through Monday during the storm. This includes both storm slabs and persistent slabs. On Wednesday, natural activity is generally not expected but is possible on steep south-facing slopes if the sun comes out. Human-triggering of the storm slab remains possible, especially on steep slopes and wind loaded features in the alpine.
Snowpack Summary
60-100cm of recent storm snow sits over the late-Jan weak layer at higher elevations. This snow is expected to be settling rapidly with the unseasonably warm temperatures. Rain has soaked the snow surface up to around 1900m and moist snow is reported to at least 2200m. Overnight cooling may be forming a surface crust at some elevations. Strong SW winds had formed wind slabs in exposed leeward terrain features. The storm slab sits on an old rain crust at lower elevations, variable surface hoar, and/or wind affected surfaces at higher elevations. The mid-January surface hoar is typically down 80-120cm and has been very reactive in some areas. The mid-December weak layer is down around 1.5m but was generally unreactive through the storm.
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.
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.