Avalanche Forecast

Issued: Mar 19th, 2015 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs, Loose Wet and Deep Persistent Slabs.

jon stuart-smith, Parks Canada

Waterton Lakes.

Winds and solar heating have continued to produce avalanche activity with the snow from last weekend. Avalanche danger will stay elevated until this snow stabilizes and temperatures cool.

Summary

Weather Forecast

Friday should be a mix of sun and cloud but with strong westerly winds and freezing level climbing to ridgetop. Saturday could see up to 5mm of precipitation, starting late in the day, with freezing level dropping down to valley bottom as the snow tapers off Sunday morning. Sunday will clear off and temperatures will start rising again.

Snowpack Summary

Surface temperature and solar crusts now exist to ridge top on S and E slopes and only to 2000m on N and W slopes. Below the storm slab from the weekend there is a new crust which will support a boot only once you reach 1900m. The strong southwesterly winds have picked up and with the snow from the W slopes are contributing to the slab development.

Avalanche Summary

Good visibility today showed evidence of previous widespread loose dry avalanches and storm slab avalanches from treeline and above which resulted in substantial moist debris piles as they reached lower elevations. Loose wet activity has been focused on mainly E and S slopes but will become more widespread as heating continues into the weekend.

Confidence

Freezing levels are uncertain

Problems

Storm Slabs

The slabs are continuing to build on N and E aspects with snow transport from strong SW winds. These will become more reactive with daytime heating. Large cornices could provide a trigger for avalanche activity and could be weakened by the heat.

Be alert to conditions that change with elevation.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Wet

As temperatures increase watch for moist snow to develop at lower elevations and climb in elevation as the day heats up. When the sun comes out this will happen quickly on solar slopes. Expect this moist snow to move easily over the buried crust.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Deep Persistent Slabs

These layers from early season are still a concern on N aspects in the alpine, especially in shallow snowpack areas. Warm temperatures penetrating the snowpack could wake up these deep instabilities.

Avoid shallow snowpack areas where triggering is more likely.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Mar 22nd, 2015 4:00PM