Regions
Northwest Inland.
New snow and wind will continue to build wind slabs in the alpine and treeline elevations. Triggering persistent slabs from thin snowpack areas remains a concern in the north of the region.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Wednesday
Weather Forecast
WEDNESDAY: Isolated flurries with accumulations of 5-10 cm / light to moderate southwest wind / alpine temperatures around -8 C.THURSDAY: Isolated flurries / light to moderate south wind / alpine temperatures around -10 C.FRIDAY: Flurries with accumulations of 10-15 cm / moderate southwest wind / alpine temperatures around -12 C.
Avalanche Summary
Most of the recent reported activity has been loose dry surface snow sluffing in steep terrain. On Monday, a large size 3 slab avalanches was reported on an east aspect at 1900 m in the Howsons.On Friday, a helicopter remotely triggered a size 2.5 wind slab from above the slope on a west aspect at 1500 m north of Kispiox. On Thursday, skiers north of Kispiox remotely triggering a size 2.5 avalanche from a safe location on a ridge that released on the adjacent slope on a northwest aspect at 1650 m. A weak layer buried late-December was the suspected failure plane.
Snowpack Summary
Strong winds have built wind slabs in exposed terrain. 30-60 cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Below, there are two crust and/or surface hoar layers that were buried in late-December and mid-December. They are 50-80 cm below the surface. In the past week these deeper layers have produced hard but sudden results in snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.
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.
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.