New snow and wind may form pockets of reactive wind slab in exposed terrain. Loose snow avalanches can be expected in the new snow on steep terrain features. Where new snow sits on a crust, avalanches can trigger easily and run surprisingly far & fast.
New snow and winds may form fresh wind slabs. They will be most likely be isolated to immediate lees of ridgecrests and roll-overs at upper elevations. They are mostly likely to be reactive where they sit over a crust.
Cornices are often fragile this time of year, especially when the sun is out. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below.
The unsettled weather begins to clear up over the weekend as a ridge of high pressure sets up over the province.
Friday Night: Scattered flurries up to 5 cm. Moderate to strong southwest wind. Alpine temperature around -8. Freezing level 1000 m.
Saturday: Scattered flurries up to 10 cm. Light to moderate northwest wind. Alpine temperatures near -9. Freezing level 1200 m.
Sunday: Sunny. Light west wind. Alpine temperature around -7. Freezing level 1600 m.
Monday: Mix of sun and cloud. Light east wind. Alpine temperature around -7. Freezing level 1600 m.
Most activity in the recent snow has been limited to loose dry sluffing over a crust.
On Thursday, a significant natural cornice failure triggered a persistent slab from the slope below size 3. This occurred on a high alpine steep east-facing slope. This is an important reminder to stay well back from ridgetops that may be corniced and avoid slopes with overhead cornice exposure especially under the current conditions where recent rapid growth and daytime warming has made them large and fragile.
Incremental snowfall continues to accumulate 5-20 cm throughout the region. Shifting wind directions from the southwest to northwest may have formed isolated pockets of wind slab on leeward slopes and behind terrain features. The new snow sits on a series of melt-freeze crusts exist on all aspects below 1900 m and solar aspects to mountain top. North aspects in the alpine hold dry wintery and wind-affected snow. The mid-pack is generally strong and consolidated.
Recent warm weather is expected to have promoted bonding around widespread crust layers formed over the last month in the mid to upper snowpack. One widespread crust from mid-March found 30-60 cm deep saw isolated instances of large solar-triggered slab avalanches during the last sunny period. The early November crust is buried down 180-200 cm with faceted crystals above and below it. These persistent weaknesses are definitely worth keeping in mind heading into the next big warmup.
