Avalanche Forecast

A weak frontal system arrives on Tuesday.

SUNDAY NIGHT: A trace of snow overnight, moderate southwest wind, low temperatures around -10 C.

MONDAY: Cloudy with some light flurries, moderate southwest wind, high temperatures around -8 C.

TUESDAY: Light flurries with up to 5 cm of new snow, strong south wind, high temperatures around -6 C.

WEDNESDAY: Another 5 cm overnight then clearing in the afternoon, moderate southwest wind, high temperatures around -6 C.

Several large natural avalanches were recently reported at Chappel Creek (see this MIN report). These avalanches occurred on south aspects at treeline elevations. Based on the depth of these avalanches, they likely failed on recently buried surface hoar and/or sun crust layers. These photos suggest a persistent slab avalanche problem may exist, but we are uncertain about the details of this problem. Extra caution should be taken on steep treeline terrain around Blue River and Valemount where there may be enough snow above this weak layer to produce dangerous avalanches.

Otherwise some small wind slab and dry loose avalanches have recently been observed in alpine terrain.

The alpine is wind-affected and lower elevations are capped by a hard rain crust. Reports suggest this crust extends up to anywhere from 1200 m to 1700 m. Sheltered areas at treeline likely have 15-40 cm of low density snow.

The main concern (and uncertainty) is whether this recent snow is bonding to a surface hoar layer and/or sun crusts. In most areas this snow has probably not developed into a concerning slab, with the exception of the Blue River and Valemount areas where there has been more snowfall. The most likely terrain for this problem is around treeline elevations where the snowpack has not been affected by wind or rain (see some good examples in these MIN photos).

 A buried rain crust can be found in the lower snowpack (50-100 cm deep) with some reports of weak snow around this crust. While we have not seen recent avalanches on this layer, it continues to produce occasional results in snowpack tests. It may be reactive to human triggers on shallow rocky slopes in the alpine or alpine-like features at treeline.

• Investigate the bond of the recent snow before committing to your line.
• Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.