North Columbia

Another day of sunshine and warm temperatures should keep surface instabilities active. Concern for persistent slab problems is still on the rise.Check out the Forecasters' Blog for more: http://www.avalanche.ca/blogs/2018-03-09-first-big-warm-up

Moderate -

Sunday: Mainly sunny. Light south winds. Freezing level to 1800 metres with alpine high temperatures around -2.Monday: Sunny. Light southeast winds. Freezing level to 2000 metres with alpine high temperatures of 0 to +1.Tuesday: Mainly sunny, becoming cloudier in the afternoon. Light to moderate southeast winds. Freezing level to 2500 metres with alpine high temperatures of +4.

Reports from Friday included observations of numerous storm slabs and wind slabs that ran from size 1.5 to 2.5. These were triggered naturally as well as with ski cutting and all aspects and elevations were represented. Many recent loose dry and loose wet avalanches were observed in the region and in adjacent regions.Thursday's reports showed several size 1 storm slabs and wind slabs releasing with ski cutting above 1800 metres. One size 1.5 was triggered by a snowmobile. A recent natural size 2 persistent slab avalanche was noted in steep, south-facing alpine terrain. It featured a 70 cm deep crown and is suspected to have failed on a crust from mid-February.On Wednesday, a few large persistent slabs failed naturally, one with a solar trigger and a couple triggered by icefall. Avalanche activity is expected to increase as we move into a period of intense sun and prolonged warming. Predictable loose wet avalanches from steep, sunny terrain should be easy to manage. A trickier problem will emerge as warmth penetrates into the snowpack to tickle deeper persistent weak layers. This will be a time to avoid exposure to large sunny features and keep well away from corniced slopes.

20-30 cm of new snow has formed storm slabs which overlie sun crusts on solar aspects. This latest snow sits on well-settled storm snow from regular snowfalls over the past couple of weeks. Several other sun crust layers may be found within this storm snow on solar aspects.A couple of layers buried in mid to late February (down around 60-110 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, these interfaces were most reactive on solar aspects, where they present as buried sun crusts. However, persistent slabs have been triggered on shady aspects too, where surface hoar and/or facets exist.Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with forecast warming, a surface avalanche stepping down, cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets linger at the base of the snowpack.