Avalanche Forecast

Moderate - Uncertainty is due to difficult to forecast freezing levels. The snowpack structure is generally well understood.

A ridge of high pressure brings warming and sunny skies through the weekend. Alpine inversions may see temperatures as high as +5 degrees with some valley bottoms possibly seeing cloud and cooler air pooling at lower elevations.

Saturday Night: Clear. No new snow expected. Ridgetop winds moderate from the northwest. Freezing level around 3000 m, with a possibility of below 0 C temperatures between 500 m and 2000 m. 

Sunday: Scattered clouds. Freezing levels rise through the day to 800 m, and an above freezing layer may stay in place, with alpine temperatures near +5 C between 2000 m and 3000 m. Possible inversion may hold valley cloud and cooler temperatures down low. Ridgetop winds moderate from the northwest. Expect cooling overnight.

Monday: Mix of sun and cloud. No new snow expected. Strong ridgetop wind from the northwest. Alpine temperatures -3 and freezing levels forecast to drop to valley bottom overnight, and back up to 750 m through the day.

Tuesday: Scattered clouds. No new snow expected. Light southwest wind trending to moderate northwest at higher elevations. Freezing level at valley bottom, rising to 500 m by the afternoon. 

Most concerning is the warm weather this weekend. Warming, solar radiation, smaller surface avalanches, and cornice fall could trigger deep persistent slabs. This layer has been dormant but the forecasted weather has the potential to wake it up. 

On Friday, several natural wind slab avalanches were reported in Kootenay Pass. They were mostly on northeast aspects at treeline. 

On Thursday, numerous storm slab avalanches were reported up to size 2. 

During the warm previous storm, mid-last week, a large widespread avalanche cycle occurred with most avalanches releasing within the storm snow and some on Jan 11 surface hoar layer. Strong solar radiation and warm temperatures were also at play after the storm, producing numerous avalanches at all elevations and scouring avalanche paths to the ground in places.

Incoming warm air may ride on top of colder air in the valleys, so the snowpack may experience above zero temperatures at higher elevations, where you may not expect them. Combine this with the potential for strong solar input, and the alpine snowpack could experience some rapid change for the worse.

10-20 cm of recent snow combined with strong winds has formed reactive wind slabs and buries a series of recent surface hoar layers and melt-freeze crusts found down 15 cm and another down 25 cm. These extend to 2400 m and are most prevalent (thicker) on southerly aspects. 

Digging deeper, down 50-60 cm is yet another surface hoar layer that has seen recent avalanche activity. A well-consolidated mid-pack exists below this and above the early December crust/facet interface. 

The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past month. The crust is now buried 120-200 cm deep except in thin, wind-affected areas near ridgetops. Warming, cornice fall, and smaller avalanches through the forecast period may be enough to wake this layer up and initiate large to very large avalanches.

• Choose simple terrain.
• Avoid terrain traps where the consequence of any avalanche could be serious.
• Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
• A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.