New storm snow accompanied by strong to extreme ridgetop wind will build touchy and reactive storm slabs on all aspects and elevations. Make conservative terrain choices.
The new storm snow will likely have a poor bond to the underlying old snow surfaces. Storm slabs will be reactive, especially on leeward slopes where deeper slabs exist due to wind loading.
An unsettled weather pattern will bring moderate snowfall amounts with possible enhancement due to the NW flow and strong ridgetop wind through the weekend.
Wednesday Overnight: New snow 10-20 cm by mid-morning on Thursday. Freezing level dropping to valley bottom. Alpine temperatures -10 and strong West to northwesterly winds.
Thursday: Snow amounts 15-25 cm by 4 pm. Freezing level rising to 1500 m. Alpine temperature near -5 with strong to extreme Northwest to West wind.
Friday: Snow 10-20 cm. Freezing level rising to 1500 m and alpine temperatures near -5. Strong West wind.
Saturday: Snow 5-10 cm. Freezing level 1100 m and alpine temperature near -8. Moderate Southwest wind.
Reactive storm slabs are likely on Thursday.
No new avalanches were reported by Wednesday afternoon.
During the rain event last Wednesday, a natural avalanche cycle occurred. Numerous wet loose avalanches were observed on all aspects and elevations. A few notable large slab avalanches were observed, which we suspect occurred during this rain event. these avalanches failed on deeper layers in the snowpack. These layers will not be a concern while a thick crust is present on the surface of the snowpack but may wake with a large amount of warming and load. Examples of these avalanches can be seen in this MIN report from the south of the region, and this report near Tumbler Ridge.
The last persistent slab avalanches associated with the late January surface hoar layer occurred on February 7th in the south of the region. These natural avalanches occurred on a shaded aspect below treeline.
Up to 15 cm of new snow fell by Wednesday morning and is expected to bond poorly to a widespread surface crust. This 1-20 cm thick crust exists on all aspects and elevations, excluding areas in the high alpine in the south of the region that may remain crust-free. In open areas in the alpine and treeline, northwesterly winds may redistribute the new snow into small but reactive pockets of wind slab in lee areas.
Below the crust, last week's 30-50 cm of storm snow buried a weak layer formed in late January. This layer consists of faceted snow, a melt-freeze crust, and surface hoar crystals in sheltered areas. This layer of buried surface hoar is becoming increasingly hard to find in the snowpack. Our field team was able to find this layer in the Pine Pass area in sheltered areas between 1250-1500 m, their full report can be seen here. Currently, this layer is bridged by a thick surface crust in most areas but will be on our radar with a significant amount of warming and new load.
The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.
