Lizard Range and Flathead Avalanche Forecast

Issued: Mar 15th, 2020 4:00PM

Mon Mar 16th Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Low
Tue Mar 17th 2 Day Outlook
Alpine Moderate Treeline Low Below Treeline Low
Wed Mar 18th 3 Day Outlook
Alpine Low Treeline Low Below Treeline Low

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

Strong northeast winds have formed wind slabs on atypical slopes. Sunny skies and a warming trend could start to weaken sun-exposed slopes and cornices.

Summary

Confidence

Moderate - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

Sunday night: Mostly clear, light northeast winds, alpine temperature -18 C. 

Monday: Clear, light variable winds, alpine high temperature -3 C, freezing level 1500 m.

Tuesday: Increasing cloud, light northeast winds, alpine high temperature near 0 C, freezing level 1500 m.

Wednesday: Mix of sun and cloud, overnight isolated flurries with trace accumulations, light northeast winds, alpine high temperature -6 C, freezing level 1000 m.  

Avalanche Summary

Several large (size 2) wind slabs were reported on Saturday releasing naturally on lee slopes above 1700 m. Numerous small (size 1) wind slabs were also reported as a result of ski cuts. Cornices have grown large with the recent weather, and a cornice failure could trigger a wind slab avalanche on the slope below. On Friday, there were reports of cornice falls triggering small wind slab avalanches. 

Cornices and loose wet avalanches may become more reactive with strong solar radiation and rising temperatures forecast for the coming days.

Snowpack Summary

Strong easterly winds have drifted recent snow into wind slabs on lee terrain features in a reverse-loading pattern. A warming trend is forecast over the next several days, which could weaken surface snow and cornices.

A total of 30 to 60 cm of snow from the previous storm has been redistributed by wind or is well-settled. This snow sits over another layer of 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/facet layer currently 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

  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Strong easterly winds have drifted the 10-20 cm of new snow into wind slabs on lee terrain features in a reverse loading pattern. These wind slabs may be possible to human trigger. Cornices may also be reaching their breaking point.

Aspects:

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

Elevations:

Alpine, Treeline.

Loose Wet

An icon showing Loose Wet

Likelihood

Possible-Likely

Expected Size

1 - 1.5

Rapidly rising temperatures and intense solar radiation may initiate wet loose avalanches and weaken cornices. This activity is likely to be most prominent on steep slopes that receive direct day-time solar radiation (slopes that face south through west). Minimize exposure to steep, sun-exposed slopes and cornices.

Aspects:

South East, South, South West, West.

Elevations:

All elevations.

Valid until: Mar 16th, 2020 5:00PM