More rain is expected today for lower elevations. New storm snow up high needs time to stabilize.
Weather Forecast
Moist and warm pacific fronts continue to hit Rogers Pass this weekend. Moderate SW winds gusting to strong and light rain below treeline with moist snow above. The next major system arrives Sat evening with increased winds and 16mm of precipitation by Sunday afternoon. Freezing levels remain just below treeline for the rest of the weekend.
Snowpack Summary
Intense rain in the last 36hrs has left the upper snowpack moist or wet to around 2100m. The Jan 30 surface hoar/crust layer, which exists up to 2200m, is down 30-70cm, depth will depend on elevation. Jan 15 surface hoar layer is down 70-110cm and was reactive in artillery highway avalanche control.
Avalanche Summary
Yesterday saw a widespread natural cycle producing large avalanches with moist deposits at lower elevations. Artillery highway avalanche control produced numerous size 3-3.5 avalanches with with wide propagating slabs on all aspects. Avalanches ran far, in some cases to the end of the run outs.
Confidence
Timing, track, or intensity of incoming weather system is uncertain
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.