Avalanche Forecast

Issued: Feb 2nd, 2019 4:19PM

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

mconlan, Avalanche Canada

Lizard-Flathead.

Recent storm snow has the potential to form large avalanches and step down to 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 -24 C.MONDAY: Cloudy with light snowfall, accumulation 5 cm, light southwest winds, alpine temperature -24 C.TUESDAY: Partly cloudy skies, light northeast winds, alpine temperature -16 C.

Avalanche Summary

Many large storm slab avalanches were triggered naturally, by skiers, and by explosives on Saturday. On Friday, skiers triggered small slabs around 10 to 40 cm deep, between 1600 m and 1900 m, likely on the weak layer described in the Snowpack Summary.

Snowpack Summary

Somewhere around 60 mm of precipitation fell on Friday with a freezing level around 1600 m. Above 1600 m, expect to find around 30 to 60 cm of new snow. This snow overlies feathery surface hoar crystals in shaded and sheltered areas, previously wind-affected snow in exposed terrain, and a melt-freeze crust on southerly aspects. Below 1600 m, the precipitation fell as rain and froze into a melt-freeze crust. Any new snow that falls on Saturday night into Sunday will accumulate onto these surfaces.The mid-January layer of surface hoar or a crust is buried around 50 to 100 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m. The melt-freeze crust is found on south aspects at all elevations.The remainder of the snowpack is generally well-settled. Thin snowpack areas, such as in the east of the region, may find weak and sugary faceted grains near the base of the snowpack.

Problems

Storm Slabs

Expect to find around 30 to 60 cm of recent snow above 1600 m. This snow may continue to be reactive to human traffic. Westerly winds may have made the touchiest deposits in lee terrain depressions, particularly near ridges.

Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.Avoid open slopes and steep terrain, since storm snow may not bond well to underlying layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

The recent storm snow is loading a weak layer of surface hoar or a crust. The surface hoar is likely best preserved in shaded and sheltered areas between 1600 m and 1900 m. The crust exists on southerly aspects at all elevations.

Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Make observations and assess conditions continually as you travel.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

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