It's still winter at and above treeline and the current avalanche problems dictate careful terrain selection.Check out the new video by the South Rockies Field Team in our blog section: www.avalanche.ca/blogs
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Monday
Weather Forecast
Sunday: Clear skies in the morning, cloud cover increasing throughout the day. Strong winds out of the SW at treeline, NW at ridgetop, backing off as the day goes on. Freezing level starting at 800m, rising to 2300m.Monday: Overcast skies. Light variable winds at all elevations. 5 to 15cm of snow possible. Freezing level starting at 600m, rising to 1500m in the afternoon. Tuesday: Scattered cloud. No significant precipitation expected. Light variable winds at all elevations. Freezing level starting at 600m, rising to 1500m in the afternoon.
Avalanche Summary
No new avalanche activity to report from Friday. A widespread natural avalanche cycle to size 2.5 occurred on Monday during the storm. These were primarily storm slab avalanches but several stepped down to deeper persistent weak layers or to the ground in steep unskiable terrain. At lower elevations, loose wet avalanches up to size 2.5 were reported as well as isolated wet slabs. Natural avalanches quickly tapered off during the storm but touchy conditions existed through the week. Winds increased on Thursday and wind slab formation has been ongoing since.
Snowpack Summary
A moist or wet snow surface is expected on all aspects to around treeline and on sun-exposed slopes into the alpine. Dry snow can likely still be found on sheltered high elevation slopes. Ongoing strong SW winds are redistributing the surface snow in exposed high elevation terrain. A weak rain crust from last weekend is down 30-50cm and has a good bond with snow above. There are a couple older persistent weak layers in the midpack that are still intact and have the potential to wake-up with substantial warming or heavy loading. Cornices may become fragile with afternoon warming.
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.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.