Avalanche Forecast

Issued: Feb 3rd, 2019 3:35PM

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

mconlan, Avalanche Canada

South Rockies.

The recent snow is of concern because it may still be reactive to human traffic and it is loading buried weak layers. Best to apply conservative route selection.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Cloudy with light snowfall, accumulation trace to 5 cm, alpine temperature -26 C.MONDAY: Cloudy with light snowfall and afternoon clearing, accumulation trace to 5 cm, light north wind, alpine temperature -24 C.TUESDAY: Mix of sun and clouds with intermittent snowfall in the south, light northeast wind, alpine temperature -21 C.WEDNESDAY: Partly cloudy, light northwest wind, alpine temperature -16 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 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Wind Slabs

Recent snow may have been redeposited with southwest winds that switched to northeast winds. The touchiest pockets will likely be 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: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Feb 4th, 2019 2:00PM