South Columbia

Fair - Timing of incoming weather is uncertain

Overnight Tuesday: Strong SW ridgetop winds. Snow amounts 15-25cms. Freezing levels could rise to 1000m. Wednesday: Ridgetop winds 60-70km/hr from the SW. Snow amounts 5-15cms. Freezing levels could rise to 1600m. Thursday: Ridgetop winds 55-90km/hr from the W. Snow amounts 5-10cms. Freezing levels dropping back down to valley bottom. Friday: Snow amounts 10-20cms. Freezing levels at valley bottom starting to rise in the evening.Check out the new Forecasters Blog Post to learn more about weather patterns, and timing in regards to how it affects our avalanche bulletins.

Natural activity up to size 2 has started to ramp up in the South Columbias. There are also continued reports of rider triggered avalanches up to size 2, and natural cornice failures triggering slopes below up to size 2. The focus is on elevations between 1500-2100m, and mainly on North-South aspects. These new avalanches suggest that the tipping point for activity on the mid-December surface hoar is happening, and the problem will likely get worse with more forecast snow, wind and rising freezing levels. Check out the Forecasters Blog to see an updated avi picture. It clearly indicates how touchy the surface hoar layer is on convexities and low angle terrain.

Up to 35cm of new snow has fallen over the past three days forming wind slabs and soft slabs in exposed open areas at treeline and above. The new snow also overlies soft slabs on North through East aspects and some spotty, small buried surface hoar/surface facets down 10-20cms in sheltered locations at treeline and below. Field tests show easy shears on this layer. The new snow is creating an additional load to a buried surface hoar layer that is found down 60-80cms in the snowpack. This layer we are referring to as the mid-December surface hoar layer. This layer has naturally reached its threshold in the southern part of the region. In the northern part it sits waiting for a trigger. This surface hoar layer is still producing sudden planar results in stability tests and a whole block rutchblock 4 was also observed. This is certainly the layer to watch; especially if it reaches its threshold by additional snow loading or rider triggers. Check out the forecaster blog for more info/ideas on this current problem. The midpack is well consolidated and strong.