North Columbia

New storm snow is not bonding well to rain-crusts and buried surface hoar. Watch for signs of instability and chose conservative terrain. 

Cooler, a mix of sun and clouds for the remainder of the week as a high pressure builds.

Wednesday Night: Mainly cloudy with isolated flurries (clear skies to the north), light Southwesterly wind, freezing level valley bottom (600m). Alpine Low -7C.

Thursday: Cloudy with sunny periods, light Southeast wind, freezing level 1000 m. Alpine High -7C.

Friday: A mix of sun and clouds, light and variable winds, freezing level 700 m. Alpine Low -10C / High -6C

Saturday: A mix of sun and clouds, light and variable winds, freezing level 700 m. Alpine Low -10C / High -7C

Avalanche hazard is highly variable and dependent on snowfall amounts and freezing lines experienced locally by this recent storm. Cooler temperatures and the passing of the storm mean that the natural avalanche cycle have tapered. However, reports are coming in reporting the poor bond of the new snow to rain crusts near the surface. 

Additionally, on Wednesday avalanche control work was able to trigger large avalanches on the Nov 5 rain crust deep persistent layer in northerly shallow rocky terrain around 2000m. This elevation would have been below the recent inversion, which further weakening the crust. Elsewhere, numerous reports have come in describing the poor bond of new snow to the recent rain crusts producing small to large avalanches.  

On Tuesday, at the peak of the cycle, reports of large avalanches (Size 2) naturally and from skier controlled and explosive control work on Tuesday . A few Very Large (Size 3) Natural avalanches were reported running to valley bottom along the highway corridor.  

Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Freezing rain with the recent storm has created a thick rain crust (or two) up to 2000m in many regions of the forecast area. Its distribution and extent remains unclear - especially in the Northern regions - but we believe it is widespread in the southern portions of the region and reports of up 1- 5cm thick near tree line. In some areas there are two rain crusts: a thin crust near the base of the recent storm snow and a second thicker crust near the surface. See this MIN report from near Crowfoot Mountain & this MIN report from the South Columbia near Hall Mountain. From the fare north region comes this MIN with reports of Rain up to 1500m.

Recent storm snowfall amounts of 20-40cm overlie a widespread large surface hoar. We suspect this layer may still be preserved in many tree line locations which were not affected by high freezing levels and rain events. In other words, if there is no rain crust at and below tree line, be on the look out for buried surface hoar.  

In the Alpine, recent winds will have redistributed snow. These storm slabs sit atop suncrust on solar aspects.  

The most notable layer in the lower snowpack is from early November rains (Nov 5 Crust), which is now sitting near the base of the snowpack and is likely surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers on shallow rocky slopes in the alpine.

• Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.