Lizard Range and Flathead Avalanche Forecast

Issued: Apr 17th, 2021 4:00PM

Sun Apr 18th Current Conditions
Alpine Considerable Treeline Moderate Below Treeline Low
Mon Apr 19th 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Low
Tue Apr 20th 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate

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

New snow and northeast wind are expected to form wind slabs in lee features at upper elevations that will likely be reactive to triggering. Stay alert to changing conditions on Sunday.

Summary

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

An upslope storm will bring varying snow totals to the region, favoring the eastern slopes.

Saturday night: Mostly clear, light west wind, alpine temperature near 0 C, freezing level 2900 m.

Sunday: Cloudy, 5-15 cm of snow, winds becoming northeast and increasing to moderate, alpine high temperature +1 C, freezing level dropping through the day to 1300 m.

Monday: Mostly cloudy, light northerly winds, alpine high temperature -2 C, freezing level 1700 m.

Tuesday: Mainly sunny, light northerly winds, alpine high temperature -2 C, freezing level 2300 m. 

Avalanche Summary

Natural wet loose avalanches, ranging from size 1-2.5, were reported over the past few days.

Snowpack Summary

An upslope storm is expected to bring enhanced snowfall to favored eastern slopes in the region throughout the day on Sunday. Amounts will generally range from 5-10 cm with pockets of up to 15 cm possible in favored areas. Precipitation will likely start as rain, further complicating the amount of snow forecast. Moderate northeast winds with strong ridgetop gusts will likely build a new reactive wind slab problem throughout the day. Cornices are large and fragile. Cornice falls could trigger avalanches on the slopes below.

The snowpack is overall strong and settled in most areas. However, steep and rocky alpine slopes with a shallow or thin to thick snowpack may still harbor deeply buried weak layers. Glide cracks releasing as full depth glide slab avalanches become more common in the spring and are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

The snow line is slowly creeping up the mountains, making some access areas snow-free. 

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Wind slabs are most reactive during their formation.
  • Extra caution is needed around cornices under the current conditions.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2

Snow totals are expected to vary across the region, but areas that see upslope enhancement may receive up to 15 cm accumulate by late afternoon on Sunday. The new snow combined with moderate northeast winds will likely form a reactive wind slab problem in lee terrain features. 

Aspects:

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

Elevations:

Alpine, Treeline.

Cornices

An icon showing Cornices

Likelihood

Possible-Likely

Expected Size

2 - 3

 Cornices are large and fragile. Cornice falls could trigger avalanches on the slopes below. 

Aspects:

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

Elevations:

Alpine.

Valid until: Apr 18th, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.