Lizard Range and Flathead Avalanche Forecast

Issued: Mar 10th, 2020 4:00PM

Wed Mar 11th Current Conditions
Alpine Considerable Treeline Considerable Below Treeline Moderate
Thu Mar 12th 2 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Moderate
Fri Mar 13th 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate

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

Wind slabs are likely to be encountered at upper elevations and will likely be reactive to human triggering. Choose conservative terrain, especially at upper elevations.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

TUESDAY NIGHT- Mainly cloudy with flurries, 5-15 cm / west wind, 30-60 km/h / alpine low temperature near -6

WEDNESDAY- Cloudy with sunny periods and flurries, 5 cm / west wind, 40-60 km/h / alpine high temperature near -6

THURSDAY- Cloudy with sunny periods / northwest wind, 10-30 km/h / alpine high temperature near -8

FRIDAY- Mainly cloudy with flurries, 5-10 cm / northeast wind, 30-60 km/h / alpine high temperature near -13

Avalanche Summary

With new snow and wind in the forecast, wind slabs will be building at upper elevations and may become more reactive throughout the day on Wednesday. Cornices are also growing large with this weather pattern and a cornice failure could trigger a wind slab avalanche on the slope below.

On Monday, there were several natural, human and explosives triggered storm slab avalanches up to size 2. These were mostly on north through east aspects around 2000 m.

On Sunday, loose dry and soft slab avalanches were sensitive to human triggering and explosives avalanche control work to size 1.5. Avalanches have been 10 to 20 cm in depth, running fast and far. 

Snowpack Summary

10-15 cm of new snow from Tuesday night with moderate to strong west winds will continue to promote slab development.

A total of 30 to 50 cm of recent storm snow sits on buried wind slabs in exposed areas and a sun crust on solar aspects (south through west facing slopes). Melt-freeze crusts extend up to 1900 m on other aspects. 

A thick crust that has facets associated with it sits 30-60 cm below the surface. There has been only one avalanche reported on this layer since February 17th. The middle of the snowpack is generally strong, but the base of the snowpack contains weak basal facets that are most prominent in shallow rocky start zones.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2.5

30 to 50 cm of total recent storm snow and strong west winds have formed wind slabs in many areas. Wind slabs will be most reactive in lee terrain features. 

Aspects:

North, North East, East, South East, North West.

Elevations:

All elevations.

Valid until: Mar 11th, 2020 5:00PM