Avalanche Forecast

Issued: Feb 2nd, 2019 4:33PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Persistent Slabs, Wind Slabs and Deep Persistent Slabs.

mconlan, Avalanche Canada

South Rockies.

All the recent snow is of concern because 1) it may not bond well to underlying layers and 2) it is loading buried weak layers. Conservative decision-making is essential!

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

SATURDAY NIGHT: Cloudy with light snowfall, accumulation 5 to 10 cm, cooling overnight.SUNDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light southwest winds, alpine temperature -27 C.MONDAY: Cloudy with light snowfall, accumulation 5 cm, light north winds, alpine temperature -29 C.TUESDAY: Mostly clear skies, light north winds, alpine temperature -18 C.

Avalanche Summary

Many small to large avalanches were triggered within the recent storm snow by skiers, naturally, and explosives on Saturday. The fact that we have numerous weak layers within our snowpack indicates that conservative decisions should be made at this time.

Snowpack Summary

Above 1700 m, 30 to 40 cm of recent snow overlies a variety of surfaces, including feathery surface hoar crystals in shaded and sheltered areas, wind-affected snow in exposed terrain, and a melt-freeze crust on southerly aspects. Below 1700 m, expect to find around 5 to 10 cm of low-density snow on a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 40 to 60 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2100 m. The melt-freeze crust is found on south aspects at all elevations.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains.

Problems

Persistent Slabs

40 to 60 cm of snow is loading a weak layer of feathery surface hoar crystals, which is best preserved in shaded and sheltered areas between 1600 m and 1900 m. On southerly aspects, the snow sits on a hard melt-freeze crust. This layer may be touchy.

Use added caution in open terrain features, such as cutblocks, gullies, and cutbanks.Be aware of the potential for wide propagation.Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 2.5

Wind Slabs

Recent snow may have been redeposited with southwest winds in exposed terrain. The touchiest pockets will likely be in lee terrain features adjacent to ridges.

Be careful with wind-loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Good day to make conservative terrain choices.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

The bottom of the snowpack consists of weak and sugary faceted snow. The consequences of triggering this layer remains high, as avalanches will be large and destructive.

Avoid steep, rocky terrain and shallow snowpack areas where triggering deep layers is more likely.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Use conservative route selection, such as moderate-angled and smooth terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Feb 3rd, 2019 2:00PM