Avalanche Forecast

Moderate

We have preliminary reports of a serious avalanche incident today near Invermere, which is directly adjacent to this forecast region. We will update this section with details as they become available.

Almost all operators in the region reported some variation of the theme of a natural and skier-triggered avalanche cycle early this week as 40-70 cm of new snow weekend settled into touchy storm slabs in some areas and produced powerful dry loose releases with rider traffic in areas where slabs hadn't quite formed. Improved travel conditions on Monday and Tuesday allowed for more observations of the aftermath of the cycle, generally observed to have produced avalanches to size 2.5 (large!) and for the most part confined to the depth of new snow. A few operators noted the cycle being less widespread than expected.

Clear skies last week allowed for observations of many deep persistent slab avalanches as well as explosive control missions, which produced large to very large (size 2 to 3.5) avalanches. Another one was triggered in Glacier National Park on Monday. These avalanches have been occurring on all aspects and generally between 2200 m and 2800 m in elevation. Although many of these avalanches have occurred in unrideable terrain, they are evidence that the weak basal snowpack is still triggerable. Riders should continue to avoid thin snowpack areas, which are often found near ridgelines.

Looking forward, moderate snowfall and elevated winds are expected to trigger an uptick in natural avalanche activity and human triggering potential through Thursday. The possibility for very large deep persistent slab avalanches should not be ruled out.

15-25 cm of new snow is expected to accumulate in the region by end of day Thursday. For the most part it will add to low density storm snow from the weekend, but it may also bury recent wind slabs in more exposed areas and likely a thin sun crust on sun-exposed aspects.

The roughly 40-80 cm of new snow from the weekend storm sits on an interface that includes small surface hoar in lower elevation sheltered areas and more widespread faceted (sugary) snow and heavy wind effect. This interface remains in question with storm slabs having been generally slow to form over it in recent days.

Around 100 to 130 cm of snow may now rest on a small layer of surface hoar crystals that was buried mid-February. This layer is most likely found around treeline elevations in areas sheltered from the wind. This layer generally appears to be dormant now but could still be capable of producing avalanches in isolated areas. The remainder of the mid-snowpack is generally strong.

A layer of large and weak facets that formed in November is deeply buried, found near the base of the snowpack. The likelihood of human triggering this layer is currently low given its depth. However, alarming reports like this one from Glacier National Park continue to trickle in, confirming it is still best to avoid steep, thin, rocky slopes near ridges at alpine and upper treeline elevations.

Wednesday night

Cloudy with flurries bringing about 5 cm of new snow. Light southwest winds increasing into the morning.

Thursday

Cloudy with continuing snowfall bringing 10-20 cm of new snow. Moderate southwest winds, strong in the alpine. Treeline high temperatures around -7.

Friday

Cloudy with continuing flurries bringing about 5 cm of new snow and storm totals to 20-30 cm. Light to moderate southwest winds. Treeline high temperatures around -8.

Saturday

Mainly cloudy with isolated flurries. Light southeast winds. Treeline high temperatures around -7.

More details can be found in the Mountain Weather Forecast.

• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.