The snowpack in the Purcells is quite spacially variable and complex. Carefully evaluate each slope before committing to it.
Confidence
Fair - Freezing levels are uncertain on Monday
Weather Forecast
A significant storm system enters the region Saturday evening bringing 30 - 40 cm of new snow. This system exits the region Sunday as freezing levels climb to 1400 m. Average seasonal temperatures return Monday while a weak ridge of high pressure builds into the forecast area.
Avalanche Summary
Avalanche obs are also quite spatially variable. Control work in the Dogtooth's produced avalanches to Size 3 running on basal facets with small loads. Just a bit south of Golden control work with large loads produced very little activity. Wind effected terrain in the region went through a natural avalanche cycle to size 2.5 on Thursday.
Snowpack Summary
The Purcell's are one of the more complex & variable snowpacks in the province right now.The region has received 70 - 130 cm of storm snow in the last week. A few shears are persisting in the storm snow, but these are healing. Winds have been predominantly out of the W, SW, but some stations have reported NW winds in the last 24 hours. I`ve received obs of surface snow that is untouched by winds, and other obs where winds have produced a wind slab avalanche cycle. It`s tough to put a pattern on what`s happening out there. I suspect it`s highly drainage dependent at the moment.The mid-December surface hoar/facet combo is down around 70 cm on the E side of the range & 230 cm on the west side. I suspect it's still susceptible to human triggering in the shallow snowpack areas.
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.
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.