Archived

Avalanche Forecast

Jan 27th, 2019–Jan 28th, 2019

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

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

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Lizard-Flathead.

Recent new snow and winds have formed slabs that sit on a weak layer. These slabs may be reactive to human triggering, especially in lee features at upper elevations.

Confidence

Moderate - The weather pattern is stable

Weather Forecast

SUNDAY NIGHT - Cloudy with clear periods / light northeast winds / alpine low temperature near -11 MONDAY - A mix of sun and cloud / light southwest winds / alpine high temperature near -10TUESDAY - A mix of sun and cloud / light southwest winds/ alpine high temperature near -8 WEDNESDAY - Cloudy with sunny periods / west winds, 10-30 km/h / alpine high temperature near -6

Avalanche Summary

On Saturday, a size 1 human triggered avalanche was reported on a northeast aspect around treeline. On Friday, a human triggered size 1 avalanche was reported on a northeast aspect at 1900 m. This avalanche reportedly occurred on the surface hoar layer that is buried 10-30 cm.

Snowpack Summary

The snow surface is likely a crust below approximately 1500 m, and on sun-exposed slopes at all elevations. Above 1500 m, the top 10-30 cm of snow is likely wind-affected. This 10-30 cm of recent snow is sitting on a weak layer of surface hoar (feathery crystals), which is most prominent around treeline. On sun-exposed slopes, the surface hoar may be sitting on a sun crust, and below treeline it may be sitting on a melt-freeze crust on all aspects.In shallow snowpack areas, the base of the snowpack is composed of facets (sugary snow). In deeper snowpack areas, the middle and lower portions of the snowpack appear to be generally strong.

Avalanche Problems

Persistent Slabs

A weak layer of surface hoar (feathery crystals) and sun crust (on solar aspects) is buried under 10-30 cm recent snow. Deposits are likely deeper and more reactive in wind-loaded areas.

Watch for signs of instability such as whumpfing, or cracking.Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2