Regions
Northwest Inland.
In the far western side of the region more snow is expected to fall. In these areas, the Avalanche Danger may be HIGH on Sunday.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
On Sunday and Monday another windy storm will impact the region. Expect between 5-15mm of precipitation per 24 hour period with freezing levels climbing from 500m on Sunday morning to 1800m by Monday afternoon. On Tuesday, expect a mix of sun and cloud with the freezing level shooting up to 2500m. Ridgetop winds should remain strong to extreme from the southwest for the forecast period.
Avalanche Summary
In recent days wind and snow promoted natural slab avalanche activity to size 2 in the Howson Range. Continued snow and wind on Sunday will promote ongoing wind slab activity with the potential to step down to deeper, more destructive persistent weak layers.
Snowpack Summary
New snow and wind forecast for Sunday will create reactive new wind slabs throughout the day adding to an ongoing wind slab problem. New snow accumulations will also add mass and reactivity to a developing slab which overlies recently buried surface hoar. This layer was observed in the Hankin area and may exist in many other places. The early or mid January surface hoar layer is generally 30-50 cm deep, although it may be buried by up to 100cm of snow in the far west of the region. Observers have found this persistent weakness on all aspects and at all elevations. It consistently produces moderate "pops" results in snowpack tests. Below this, the Boxing Day surface hoar problem may also be lurking. The mid and lower snowpack is generally quite weak and faceted, especially in lower snowpack areas such as the Babines.
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.