South Columbia

Keep watching for signs of slab formation and reactivity in the new snow and be ready for solar radiation to promote instability on Tuesday.

Moderate -

Tuesday: Cloudy with sunny periods. Winds light from the southwest. Alpine temperatures of -14.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light from the south. Alpine temperatures of -8.Thursday: Periods of snow delivering 15-25 cm of new snow. Winds moderate to strong from the south. Alpine temperatures of -3.

Reports from Saturday and Sunday include numerous Size 1-2 storm slabs being triggered both naturally and with ski cutting and skier traffic, as well as with explosives control. These soft slab avalanches have been noted as very reactive to skier traffic, fast-running, and capable of entraining large amounts of loose snow.As for Tuesday's outlook, our fresh storm slabs should be expected to remain sensitive to light triggers, especially where they overlie weak layers present at our previous surface and where exposure to wind has promoted slab formation. Loose snow avalanches have also begun to evolve into a significant hazard and should not be underestimated in terrain where they have the potential to entrain significant mass.

Up to 30 cm of new low density snow from Sunday night has brought our new snow totals from the past few days to around 40-80 cm. Our new snow has buried a range of different surface conditions that developed last week. These previous surfaces include wind slabs on a variety of aspects in wind-exposed terrain, sun crust on steep solar aspects, faceted snow, as well as surface hoar found growing on sheltered open slopes in the days before the storm. The bond of the new snow to these underlying surfaces will take some time to form, and touchy conditions should be expected both at this interface as well as at mid-storm interfaces within the new snow. A persistent weakness buried mid January is now down 50-100 cm and consists of buried surface hoar in sheltered areas, sun crust on south aspects, and/or widespread faceted old snow. It has generally stabilized but may be sensitive to triggering in isolated areas where buried surface hoar is preserved. The mid and lower snowpack are generally well settled and stable.