The avalanche danger will increase as a storm moves in through the day. Choose mellow slopes and give the snowpack time to adjust to the new load. Avoid shallow, rocky start zones. Uncertainty about deeper weak layers demands vigilance, and careful terrain selection.
Triggering persistent slab avalanches remains possible due to several weak layers in the top metre of the snowpack. Facet layers are the primary concern in alpine terrain, while preserved surface hoar layers are the concern in treeline terrain.
Avalanches that start in fresh storm slabs may step down to these deeper layers.
As a new storm moves in from the coast, watch for reactive storm slabs to form through the day. They may be most reactive late in the afternoon. This storm is likely to hit earliest and hardest in the more southern and more coastal parts of the forecast area.
Over the weekend, east of Kispiox, a couple of small, rider triggered avalanches were reported. Both started as thin storm slabs failing on a layer of weak, feathery, surface hoar crystals. One of the two stepped down to a layer of weak, sugary, facetted crystals that were buried on December 23rd.
Fresh snow will be falling mostly on 20-50 cm of settled snow. In sheltered areas, a layer of weak, feathery surface hoar crystals buried in early January will now be 40-70 cm below the surface. Expect a shallower, weaker snowpack in wind exposed terrain, due to previous scouring by southeast through southwest wind.
Several persistent weak layers may be found in the top meter of the snowpack. These include a surface hoar layer buried on Dec 28 found 40 to 80 cm deep and a facet layer buried on Dec 23 found 60 to 100 cm deep. In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets. In treeline terrain, the layers are most likely triggered on steep slopes in open trees where they present as preserved surface hoar.
Monday Night
Cloudy. 0-2 cm of snow expected. Light to moderate south alpine wind. Treeline temperature around -5°C.
Tuesday
Cloudy. Possible clear periods in the north end of the forecast area. 5-20 cm of snow expected. Higher amounts are in the south west quarter of the forecast area. Alpine wind moderate to strong from the southeast. Treeline temperature around -5°C.
Wednesday
Mostly cloudy, possible clear periods. Moderate to heavy snowfall possible, different models suggest the bulk of the snow could come either tuesday or wednesday. Moderate southwest alpine wind. Treeline temperature around -5°C.
Thursday
Mostly cloudy. 2-5 cm of snow expected. Moderate southwest alpine wind. Treeline temperature around -10ºC
More details can be found in the Mountain Weather Forecast.
