Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Tuesday
Weather Forecast
A strong westerly flow is setting up for Tuesday with average seasonal temps. The big story is the wind. Winds are forecasted to be out of the W in excess of 100 km/h at ridgetop all day Tuesday. Precipitation will begin to fall Tuesday afternoon continuing into the night, there should be 15 - 20 cm of new snow out of this pulse by Wednesday morning. A second system of lesser intensity moves through the area Wednesday/Thursday producing around 10 cm of snow. Thursday afternoon and Friday look to be generally dry.
Avalanche Summary
The region saw a direct action avalanche cycle to size 2.5 Saturday & that activity continued into Sunday. Avalanches have been reported on all aspects in the alpine & at treeline. I expect natural avalanche activity to taper Monday, but the region is primed for human triggered avalanches. Natural activity will pick back up Tuesday as the next pulse delivers monster winds out of the W/SW and 15 mm or so of precip.
Snowpack Summary
The region received between 30 & 70 cm from the weekend's storm with the west side picking up the larger amounts. Three different shears have been reported in the storm snow. While these more superficial instabilities will likely settle out pretty quickly, we need to think about what all this new snow is sitting on. Remember the cold snap last week? Those cold temperatures drove faceting and created very dry loose snow that is now buried 40 - 100 cm deep. If you were out recreating on Monday you no doubt observed that the snow is settling into a soft slab. Out in the wind exposed areas there is an abundance of snow available for slab formation and a widespread wind slab avalanche problem has been observed across the region. This problem will be further exacerbated as winds are forecasted to be in excess of 100 km/h Tuesday.Various surfaces buried in early January including a rain crust, spotty surface hoar and preserved stellar snow crystals are now about 80-100cm deep and may provide a sliding layer for storm-related avalanches. A surface hoar layer buried in mid-December is gaining strength, but professionals are still treating it with caution as the consequences of an avalanche on this layer would be high. Occasional hard, planar results have been reported on this layer in snowpack tests. It's now down about 140cm in the snowpack.
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.
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 Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.