Not much change expected with only light snowfall amounts in the forecast. Watch for touchy wind slabs and cornices at upper elevations. And avoid shallow, rocky areas where triggering a deeper layer may still be possible.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Sunday
Weather Forecast
SATURDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind light, west. Temperature -8. Freezing level valley bottom.SUNDAY: Flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, west. Temperature -7. Freezing level valley bottom.MONDAY: Mix of sun and cloudy, light flurries. Accumulation trace. Ridge wind light, west. Temperature -8. Freezing level valley bottom.
Avalanche Summary
Thursday there were reports of large (size 2.5 and 3) natural cornice triggered avalanches on northerly aspects above 2400 m. One of these, the cornice collapse initiated a slab failure at the base of the snowpack, 250 cm deep. On Wednesday there were reports of several skier triggered slab avalanches up to size 2 on predominantly steep, south-facing features failing on the crust/surface hoar interface buried mid-February.Tuesday there were reports of a skier triggered size 2.5 cornice failure that produced very large, bus-sized cornice chunks on an north aspect at 2400m. As well as a size 1.5 natural wind slab failure (50-70 cm deep) on a west aspect at 2050 m.On Monday we received reports of a cornice triggered size 2.5 slab avalanche on a high north east alpine face near 2900 m, as well as natural wind slabs to size 2.5 (crowns 20-40cm thick) on a wide range of aspects above 1900m elevation. Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.
Snowpack Summary
A light dusting of new snow on Friday now covers storm snow totals from last week that range from15-30 cm, with closer to 50 cm in the very south of the region near Kimberley. Moderate south west through north west winds have redistributed these accumulations into deeper, reactive slabs in wind-exposed terrain. These accumulations sit on an interface that was buried mid-February consisting of; a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects, and surface hoar on sheltered slopes.Below the snow surface several persistent weak layers make up a complex snowpack that is slowly beginning to show sign of improving but still remains suspect. In the top 80-120 cm of the snowpack, two surface hoar/ crust layers buried in January can be found. Expect to find one or other of these on all aspects and elevations.Deeper in the snowpack (around 150 cm deep) is a facet/crust/surface hoar layer from December that is most prevalent at treeline and below.Near the base of the snowpack is a crust/facet combo from late November.
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.