Rapid loading has created very dangerous avalanche conditions. It will take a few days for the snowpack to adjust to the new load. Until then, natural and human triggered avalanches are likely.
Weather Forecast
The "pineapple express" will begin to weaken today, but we still expect up to 15cm of snow today, strong SW winds and mild temps with freezing levels hovering around Rogers Pass. A ridge of high pressure builds on Sunday. Cooling temps should start to tighten up the snowpack, the winds and precip will taper off, but the sun may trigger avalanches.
Snowpack Summary
35cm of heavy snow in the last 24hrs and a total of 60cm in 48hrs is settling with warm temps. This has rapidly loaded the Feb 12 surface hoar/crust layer down ~1m. This layer is most prevalent at and below treeline. In the alpine, S'ly winds are transporting snow rapidly loading slopes and forming new windslabs. It rained up to 1300m yesterday.
Avalanche Summary
Rapid loading by snow and moderate southerly winds triggered a widespread natural avalanche cycle yesterday. 35 size 2-2.5 and 20 size 3-3.5 natural avalanches were observed along the highway. In avalanche control yesterday, 97 rounds of artillery were fired with the majority triggering size 2-3.5 avalanches, and one size 4.
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.
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.