Regions
Northwest Inland.
A persistent slab above a crust may take time to stabilize. Evaluate the terrain and snowpack carefully before committing to steeper terrain.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
FRIDAY: Unsettled weather with isolated flurries, moderate south wind, alpine temperature around -5 C.SATURDAY: More flurries with accumulations up to 5 cm, strong south wind, alpine temperature around -7 C.SUNDAY: Mix of sun and cloud, light southeast wind, alpine temperature around -7 C.
Avalanche Summary
Reports from Wednesday are limited to several size 1 loose wet avalanches running on a sun crust at lower elevations. On Tuesday, a skier near Hazelton remotely triggered a size 1 avalanche that subsequently triggered two other size 2 avalanches on a persistent weak layer (30 cm deep). The avalanches occurred on northeast aspects at 1400 m. On Monday, a size 3 slab avalanche was triggered by a cornice fall on a north aspect at 1700 m north of Kispiox. Over the weekend, several reports describe reactive slabs above a crust, including a size 2.5 snowmobile-triggered avalanche in the Telkwas and a size 2 skier-triggered wind slab north of Kispiox.The cooling trend should help stabilize the persistent slab, but human triggering is still possible in steep or unsupported terrain.
Snowpack Summary
Unsettled weather with moderate winds is redistributing snow in exposed terrain. Recent warming and sun have likely left a crust on solar aspects and below 1300 m. Recent snow has settled into a 20-60 cm thick slab above an older crust interface. Recent reports suggest the bond to the crust is poor and has resulted in a reactive slab. Weak sugary snow near the ground has been a dormant instability, but it may still be possible to trigger in steep rocky terrain.
Problems
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.