Archived

Avalanche Forecast

Feb 3rd, 2019–Feb 4th, 2019

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Lizard-Flathead.

Wind slabs may linger with the cold temperature. If triggered, they have the potential to step down to a buried weak layer.

Confidence

High -

Weather Forecast

SUNDAY NIGHT: Cloudy with light snowfall, accumulation trace to 5 cm, alpine temperature -24 C.MONDAY: Cloudy with light snowfall and afternoon clearing, accumulation trace to 5 cm, light northeast wind, alpine temperature -20 C.TUESDAY: Mostly cloudy with intermittent snowfall, light north wind, alpine temperature -20 C.WEDNESDAY: Partly cloudy, light west wind, alpine temperature -18 C.

Avalanche Summary

Many large storm slab avalanches were triggered naturally, by skiers, and by explosives on Saturday. The avalanches likely released at the base of the storm snow as well as within the weak layer of surface hoar buried mid-January described in the Snowpack Summary.

Snowpack Summary

Around 60 mm of precipitation fell on Friday with a freezing level at 1600 m. Above 1600 m, the precipitation fell as snow, which has been redistributed by northwest winds. It may sit on weak and feathery surface hoar crystals in shaded and sheltered areas. Below 1600 m, the precipitation fell as rain and froze into 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. 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.

Avalanche Problems

Wind Slabs

Recent snow above 1600 m has been redeposited with southwest winds that switched to northeast winds. The touchiest deposits will be in lee terrain depressions, particularly near ridges.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3