Watch for changing conditions Monday as northwest winds reverse load soft snow into wind slabs in atypical terrain features. Wind slabs may sit over a crust which makes a slick bed surface for avalanches.
Upper level winds are forecast to pick up Sunday night and Monday. Watch for freshly formed wind slabs at upper elevations. Northerly wind reverse loads snow into atypical terrain features, including south facing aspects which may have a sun crust. Below 2100 m, wind slabs may sit on a rain crust which makes a slick bed surface for avalanches.
Sunday night: Clear. Strong winds above 2500 m, light below 2000 m. Alpine temperature around -12 °C. Freezing level valley bottom.
Monday: Partly cloudy. Possible trace of snow expected. Moderate to strong northwest ridgetop wind easing in the afternoon. Alpine high around -3 °C. Freezing level rising to around 1500 m.
Tuesday: 5-10 cm of snow overnight, then mostly cloudy. Light wind. Alpine temperatures around -11 °C. Freezing level dropping to valley bottom.
Wednesday: A mix of sun and cloud. Light wind. Alpine high around -15 °C. Freezing level valley bottom.
Good visibility on Sunday allowed observation of 2-3 day old storm slabs up to size 2.5 in the Castle backcountry. In neighboring Waterton National Park, ski cuts produced storm slabs and loose dry avalanches up to size 1.5.
On Saturday, south of Crowsnest Pass, a few small, rider triggered loose dry avalanches were reported on sunny slopes.
On Friday, numerous natural, rider triggered, and explosive triggered dry loose avalanches up to size 1.5 were reported in the new storm snow.
On Thursday, small, loose dry avalanches were reported in the recent storm snow. Also, south of Crowsnest Pass, one size 2 explosive controlled avalanche was reported, starting as a storm slab, and getting larger as it entrained loose new snow lower on the slope.
Northwesterly winds forecast to pick up in the alpine Sunday night and Monday will likely reverse-load 10-35 cm of dry, low density surface snow into atypical terrain features. This recent snow sits over a rain crust on all aspects as high as 2100 m. A sun crust may exist at the surface on steep south facing slopes and below 1500 m.
Recent snowfall amounts have varied widely through the region with south of highway 3 receiving 30-50 cm and the north getting 10-20 cm. The recent storm snow still needs time to bond to a variety of old surfaces such as firm wind-pressed snow, sun crust on solar aspects, and potentially weak, sugary crystals buried in late February.
The middle and lower snowpack are generally well consolidated, with a crust/facet layer from early December found near the ground. It is currently considered dormant but could become active later this season.
