Remember that the spring's strong solar radiation can weaken the snow rapidly.
Be also mindful that persistent instabilities are highly unpredictable.
Strong solar radiation will quickly destabilize the recent snow which may bond poorly to the underlying surfaces. Avoid steep sun-exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
The base of the snowpack remains very weak and avalanches are unpredictable. Very large human-triggered avalanches are possible at treeline and above. Avoid thin, rocky start zones and shallow areas with variable snowpack depths where you are most likely to trigger this layer.
Several dry loose avalanches (size 1) were naturally triggered within the recent snow on steep northerly alpine features near St.Mary's on Saturday.
Last Wednesday, a very large natural deep persistent was observed north of Elkford. This avalanche occurred on a southwest aspect in the alpine, likely as a result of strong solar radiation. It ran to valley bottom and took out the Smith Basin trail.
While activity may have started to taper off on the deeper layers, nearby avalanches are a reminder that the layers are likely still reactive in some locations in the region, especially thin, rocky areas in the alpine.
At upper elevations, up to 15 cm of recent snow overlies a crust on solar aspects, faceted snow and surface hoar up in shaded and wind-sheltered areas. Wind-affected surfaces are found in exposed areas. At lower elevations, a crust exists on or near the surface.
In the middle of the snowpack, there are at least a couple of lingering persistent weak layers, including surface hoar in wind-sheltered terrain and a sun crust on south aspects. These layers appear to have generally gone dormant but could still be reactive in isolated areas and should be on your radar in the Purcells part of the region.
The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. This weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.
Unsettled weather will continue to bring scattered flurries Monday night. The region will be under a building ridge of high pressure, with calm and dry conditions for most of the week.
Monday night
Cloudy. Lingering flurries. Trace accumulation. Low alpine temperatures of -8 °C. Light southwest ridge wind. Freezing level at valley bottom.
Tuesday
A mix of sun and clouds. High alpine temperatures of -3 °C. Light easterly ridge wind. Freezing level rises to 1500 metres.
Wednesday
A mix of sun and clouds. High alpine temperatures of -1 °C. Light easterly ridge wind. Freezing level rises to 2000 metres.
Thursday
A mix of sun and clouds. High alpine temperatures of -1 °C. Light easterly ridge wind. Freezing level rises to 2000 metres.
More details can be found in the Mountain Weather Forecast.
