The Park is under an intense storm this morning. Expect a widespread avalanche cycle when the winds increase later today.
Weather Forecast
A southwest flow is bringing warm air and heavy precip to the park today. Periods of snow are forecast today with 15 cm of snow forecast today, and 10 cm more tonight. Expect ridge top winds around 35 km/h from the SW, gusting to 90km/h today and freezing levels rising to 1100m. Snow continues on Sunday and Monday with elevated freezing levels.
Snowpack Summary
High density new snow is rapidly loading previous lower density layers resulting in a touchy surface slab. At valley bottom, a fast shear layer down 35cm is resulting in avalanches, even below treeline. At treeline this layer is expected to be 50cm deep. The Nov 28th surface hoar may be reactivated by the rapid loading or step down avalanches.
Avalanche Summary
Numerous natural avalanches were observed along the highway corridor yesterday on all aspects, running in the storm snow. Most avalanches were sized 1.5 to 2.5, with 4 sized 3.0. A field team yesterday triggered a size 1.0 avalanche at 2000m, east aspect. Obs are limited this morning, however it seems that several events have run to valley bottom.
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.
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.
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.