Avalanche Forecast

Issued: Feb 10th, 2017 4:00PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

We are just reaching the tail end of a widespread cycle of large natural avalanches. Begin your weekend with very conservative terrain choices, avoid high-consequence terrain, and watch for indications of instability.

Summary

Weather Forecast

A cooling/drying trend through Saturday, then warming into next week.Saturday: Light snowfall (with Extreme winds) eases early Saturday to Flurries and Strong Westerly winds. High -8Sunday: Mainly clear, Strong Westerlies. Treeline High of -7. Alpine Temperature inversion. Monday: Clear, Moderate Westerlies. Temperature inversion, highs near 0.

Snowpack Summary

On Thursday, rain fell below 1850m, with 10-40cm snowfall above redistributed by Strong SW - W winds, adding more load atop 120cm of recent storm snow from last weekend. This all sits on crust, or facets, Below Treeline; and hard smooth surfaces in all open areas. Facets deep in the snowpack (& a deeper crust) may be reactive under the new load.

Avalanche Summary

On Thursday and Friday, fresh Natural avalanche activity was visible in most paths observed. Many of these were large (Size 2 - 3). This included numerous avalanches from windward and front range locations that are typically wind-scoured scree, but are now holding snow. Natural triggering is expected to taper off over the weekend.

Confidence

Due to the number and quality of field observations

Problems

Wind Slabs

Strong Westerly winds have plenty of snow to move around at Treeline and above. Combined with warm temperatures, wind slabs will be growing in size. This problem will be most reactive on Saturday. These may be hard and stubborn in the alpine.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Storm Slabs

Likelihood of Storm Slabs in previous storm snow will decrease somewhat during the forecast period; however, they may be slow to bond with old surfaces, and can be surprising deep.

The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

Several large avalanches have been observed from previously shallow terrain, where storm snow fell on large facets. Observations have been limited; it is possible that Persistent slabs may be triggered in deeper areas also.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Valid until: Feb 13th, 2017 4:00PM