South Columbia

Ongoing light snowfall and moderate winds Sunday night should continue to build wind slabs and cornices at higher elevations.  Use extra caution on solar aspects and around cornices if the sun comes out Monday afternoon.

Moderate -

5-10 cm of new snow is forecast for Sunday overnight with moderate southwest wind in the alpine. Another 5-10 cm is expected on Monday with light alpine wind and freezing levels reaching around 1500 m in the afternoon. Tuesday is expected to be mainly cloudy with sunny breaks in the morning and light snow in the afternoon. Alpine wind is forecast to be light to moderate from the southwest and freezing levels are expected to reach around 1500 m. Similar unsettled conditions are currently forecast for Wednesday with sunny breaks and light snowfall both possible.

On Saturday, natural storm slab and wind slab avalanches up to size 2 were observed in the alpine above 2200 m elevation on northwest through east aspects. A few natural cornice releases triggered wind slabs up to size 2.5 on north and east aspects. Skiers triggered a few size 1 wind slabs and loose wet avalanches. Most of the recent slab avalanches were 10-30 cm thick slabs. On Friday, numerous small human triggered avalanches were reported in the top 20-30 cm of storm snow on northerly aspects above 1800 m. Explosive control produced a size 1.5 cornice chunk that did not trigger a slab on the slope below. On Thursday, several size 1.5-2 wind slabs were skier triggered and a natural cornice release triggered two pockets of deep slab in extreme terrain. On Monday, the recent storm snow is expected to be reactive at higher elevations, especially in wind loaded terrain and on steep convex features. Cornices are large and may become weak with daytime warming or during stormy periods. We are in a low probability, high consequence scenario for persistent slab avalanches failing on deep buried weak layers. Click here for more details. Click here for photos the avalanche cycle last week.

20-50 cm of snow has now accumulated over the past week which overlies a rain crust below around 2000 m or a sun crust on solar aspects at higher elevations. Alpine wind has recently been strong mainly from south through west directions and has loaded leeward slopes in exposed terrain at treeline and in the alpine. Large cornices are also reported in the alpine. At lower elevations, there may be multiple crust layers in the upper snowpack which are now generally well bonded and stable. At higher elevations, the February weak layers are down 120-150 cm and woke up during last week's storm with many avalanches stepping down. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls also stepped down to these layers last week resulting in some very large full depth avalanches.