South Columbia

Sun exposure and afternoon warming will maintain the potential for large destructive avalanches. Conservative terrain choices with low overhead exposure are essential.

Moderate - Timing or intensity of solar radiation is uncertain

A ridge of high pressure dominates for the next several days.  A mix of sun and cloud is expected on Wednesday with light alpine winds from the west.  Freezing levels are expected to drop below valley bottom overnight and reach around 1600m in the afternoon.  Mostly sunny conditions are expected for Thursday with light westerly winds and freezing levels reaching around 1800m in the afternoon.  Mostly sunny conditions are expected on Friday with moderate southwest winds in the alpine and freezing levels reaching well over 2000m.

On Monday, numerous size 1-2 natural and human-triggered avalanches were reported in the region. One natural size 2 persistent slab released on the early February surface hoar layer 60cm deep on a northeast aspect at 2100m.  A couple natural storm slabs were reported on south aspects, one on a northeast aspect at 2000m, and a wind slab on an east aspect at 2100m.  These slabs had typical thickness of 15-30cm.  Skiers also triggered a few small storm slabs with thickness of 20-30cm. More concerning is a couple persistent slabs that were human-triggered.  One was on a north aspect at 1750m and released down 80cm on the early-Feb surface hoar.  This was triggered on a steep convex boulder field feature.  This other was reported on an east aspect at 1750m and released down 80-100cm on the early Feb surface hoar.  Reports from Sunday include more evidence of natural wind slab avalanches and cornice failures from Saturday, as well as ongoing natural cornice and wind slab activity up to Size 3.5. Human triggering was also reported with skier triggered storm and wind slab avalanches up to Size 1.5 and explosives triggering up to Size 3, a few of which failed on surface hoar down 60-70cm.

10-20cm of new snow on Sunday night buried surface hoar and/or sun crust in most places. Weaknesses exist within 60-90 cm of settled recent storm snow, which is sitting on a crust buried on February 10th. In some areas there is a weak layer of surface hoar at the interface between the storm snow and the crust. The bond between the crust or surface hoar remains suspect. Moderate winds have created areas of wind slab in the lee of west or southwest winds that may be close to a metre deep. Wind slabs in motion may trigger the persistent weak layer on the crust and result in wide propagations and very large avalanches. Surface hoar buried in early January now lies up to 200cm below the surface and has become less of a concern. Possible triggers for this deep and destructive layer include a large cornice fall, strong sunshine, or significant warming.