Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Regions
North Columbia.
Conditions are tricky with a slowly increasing load over multiple weak layers in the snowpack. Take a conservative approach to your terrain choices.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Sunday: 10-15 cm snow. Moderate southerly winds. Alpine temperature near -5.Monday: 15-20 cm snow. Moderate to strong south-westerly winds. Alpine temperature warming in the afternoon to near -1.Tuesday: 5-15 cm snow. Moderate south-easterly winds. Alpine temperature near -5. More information can be found in the Mountain Weather Forecast.
Avalanche Summary
On Saturday we received preliminary reports of a human-triggered Size 2.5 avalanche in Glacier National Park, on a south east aspect near 2400m. Although the spike of avalanche activity from Wednesday has decreased, on Friday we still received reports of storm slabs to Size 2.5 running on northerly aspects above 1900m. Persistent slabs to Size 3 were also reported on Friday, remote-triggered by humans and also directly triggered by explosives.With incremental loading on Sunday, human triggering will remain likely and avalanches could be surprisingly large due to the structure of the snowpack.
Snowpack Summary
The current snowpack is complex, with three active weak layers that we are monitoring.60-90 cm of storm snow sits on a crust and/or surface hoar layer from mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and was reported at treeline elevations and possibly higher. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, the early-January persistent weak layer is 80 to 100 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is found at all elevation bands. Snowpack tests show sudden fracture characters and signs of instability such as whumpfs, cracking and avalanches. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 150 cm deep. It is most problematic at and below tree line. A rain crust buried in November is generally 150 to 200 cm deep.
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.