Avalanche Forecast

Very limited observations from the weekend storm showed small dry loose avalanches releasing with skier traffic below treeline. We also expect some degree of a natural avalanche cycle took place at higher, wind affected elevations, especially in areas that were on the higher end of our new snow totals. This MIN report from Westridge is definitely in line with the conditions we expect to persist through Tuesday.

Many small to large (size 1 to 2.5) wind slabs were triggered naturally and by riders over the past few days. They mostly occurred on south to west aspects at alpine elevations resulting from northeasterly outflow winds. A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over the week, which likely occurred during very windy conditions.

Looking forward, storm slabs from the weekend may remain sensitive to human triggering a bit longer than usual, owing to the weak faceted snow they overlie. Otherwise we expect surface instabilities to gradually become more focused toward wind loaded areas.

Stormy conditions over the weekend brought up to about 50 cm of new snow to the region along with strong southwest wind on Saturday. The new snow buried an interface which includes reports of faceted (sugary) surface snow, small surface hoar in lower elevation sheltered areas, and more widespread heavy wind effect and wind slabs at higher elevations from recent northeast winds.

Prior to the storm, a small layer of surface hoar crystals could be found about 50 to 100 cm deep, particularly in areas sheltered from the wind around treeline. This layer appears to be gaining strength and is currently considered dormant, but could have woken up in isolated areas from the weight of the new snow.

Large and weak facets that formed in November are found near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.

Monday night

Mainly cloudy with isolated flurries. Light east winds.

Tuesday

Mainly cloudy with isolated flurries. Light east winds becoming variable. Treeline high temperatures around -9 °C.

Wednesday

Cloudy with isolated flurries, increasing in late afternoon and overnight. Winds increasing to Moderate southwest by end of day. Treeline high temperatures around -10.

Thursday

Cloudywith continuing snowfall bringing 10-15 cm of new snow, including overnight amounts. Strong southwest winds easing a bit over the day. Treeline high temperatures around -8.

More details can be found in the Mountain Weather Forecast.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
• Brief periods of sun could quickly initiate natural avalanche activity.