Avalanche Forecast

Issued: Feb 13th, 2017 4:41PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Loose Wet.

rbuhler, Avalanche Canada

Cariboos.

Extra caution is required on Tuesday as freezing levels climb to mountain top elevation and the snowpack sees major warming for the first time this winter. Avoid steep sun exposed slopes during the heat of the afternoon.

Summary

Confidence

Moderate -

Weather Forecast

On Tuesday, sunny conditions are expected with moderate alpine wind from the southwest in the morning becoming strong in the afternoon. Freezing levels are forecast to reach around 2800 m with a temperature inversion keeping the valleys colder than the alpine. A layer of valley fog may also develop. On Wednesday, mostly cloudy conditions are expected with light rain beginning in the afternoon. Alpine wind is forecast to be strong from the southwest and freezing levels are expected to remain at around 2500 m. Light rain is forecast to continue Wednesday night and Thursday. 5-10 mm of precipitation is currently forecast between Wednesday afternoon and Thursday evening. Freezing levels are forecast to drop to around 2000 m on Thursday.

Avalanche Summary

On Sunday, four solar triggered size 2 storm slab avalanches were observed on southeast and south aspects at 1400-2200 m. Ski cutting produced two size 1 storm slab avalanches on southeast aspect at 1850 m. Over the weekend, several rider triggered avalanches were reported on the MIN including a size 3 that resulted in a full burial. Click here more details (1). (2), and (3). On Saturday, a natural size 2 storm slab was observed and a size 2 storm slab avalanche was remotely triggered from 60 m away.On Tuesday, storm slabs overlying a weak layer are expected to remain reactive to human triggering. Persistent slab avalanches are possible and smaller avalanches may step down. Extra caution is recommended during the heat of the afternoon, especially on sun exposed slopes. This will become increasingly important through the week as freezing levels remain very high. We have entered the first period of substantial warming following months of sustained cold conditions. Any weaknesses lingering in the snowpack will be tested in the coming days.

Snowpack Summary

The storm snow from Thursday and Friday is settling quickly due to the recent mild temperatures. The snow surface is expected to have undergoing some melting on Monday afternoon on sun exposed slopes. Recent strong winds from the south and west had redistributed the recent storm snow in exposed terrain forming touchy wind slabs. The early February weak layer is typically down 40-70 cm and includes old hard wind slabs and crusts as well as faceted snow and surface hoar on sheltered open slopes. The persistent weakness buried mid-January is now down around 80-100 cm and the surface hoar/facet weakness buried mid-December is down 100-150 cm. These deep persistent weaknesses have the potential to wake up and become reactive with the warmer temperatures.

Problems

Storm Slabs

The recent storm snow overlies a weak layer and remains reactive to human triggering, especially in wind loaded terrain. Natural activity is possible from sun exposed slopes during the heat of the afternoon. Cornices are also expected to become weak.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid recently wind loaded features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Persistent slab problems may be back in play with the new load that has been added to the snowpack and the current warming and sun. Stick to supported terrain and exercise extra caution where the new snow lies over a previously shallow snowpack.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.If triggered the storm slabs may step down to deeper layers resulting in very large avalanches.Use extra caution around steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 4

Loose Wet

Solar triggered sluffing is expected from steep sun exposed slopes during the heat of the afternoon. Sluffs have the potential to trigger slabs on the slopes below.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.Use extra caution on slopes if the snow is moist or wet.

Aspects: North, North East, East, South East.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 14th, 2017 2:00PM