Avalanche Forecast

Low - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

A ridge of high pressure builds on Saturday bringing dry and sunny conditions with mild temperatures. 

Friday Night: Snowfall 5-10 cm, moderate SW wind, treeline temperature around -5 °C. 

Saturday: A mix of sun and cloud, light to moderate W-NW wind, freezing level reaching as high as 1500 m. 

Sunday: Mainly sunny, moderate W wind, freezing level reaching as high as 1800 m. 

Monday: A mix of sun and cloud, moderate W wind, freezing level as high as 1800 m. 

On Thursday, three natural size 1-1.5 wind slabs were reported on east through south aspects at 2200 m elevation. This MIN report describes a snowmobile-triggered size 1 slab on an east aspect below treeline failing down 30 cm on the January 30 surface hoar.

Earlier in the week, shooting cracks and whumpfing had been reported which indicates the buried surface hoar layer is very weak. So far, this layer has primarily produced avalanches in wind loaded terrain but if warming causes a slab to form, a more widespread persistent slab problem should be expected. 

Prior to Friday's storm, up to 40 cm of snow from last Sunday buried the January 30 interface which consists of a melt freeze crust at lower elevations and on solar aspects extending into the alpine and widespread surface hoar in sheltered areas at and below treeline which is typically up to around 20 mm in size and very weak in some places. Prior to Friday's storm, the older storm snow had not formed a slab in most places except for where it was wind loaded. With warming and sun this weekend, rapid settlement is possible and this may result in the formation of a more widespread reactive slab over the weak surface hoar and crust. Ongoing wind over the past week has formed reactive wind slabs in exposed terrain at higher elevations and new wind slabs may build during Friday's storm.

The widespread January 18 rain crust is now around 40-50 cm deep with weak faceted snow above. This layer has not produced any recent avalanche activity but will get tested this weekend with warming and sun.

The early December crust/facet persistent weak layer is now 100-200 cm deep. This layer produced numerous large avalanches in January but is now considered dormant. We continue to track this layer of concern and expect it will wake up again with sustained warming or a large storm event. This recent forecaster blog goes into more details on the layer.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
• Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
• The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.