Avalanche Forecast

Issued: Feb 12th, 2017 4:00PM

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

jonas hoke, Parks Canada

Waterton Lakes.

The upper elevations may get there first dose of above freezing temperatures in a long time this week. Be extra cautious during the heat of the day.

Summary

Weather Forecast

A strong ridge of upper level high pressure will dominate the weather pattern for the next few days.Monday: Clear, Light SW ridge top winds, freezing level to 2500m (inversion possible)Tuesday: Clear, Light-Moderate SW ridge top winds, freezing level 3100m (inversion possible)Wednesday: Clear, Strong SW ridge top winds, freezing level to the moon.

Snowpack Summary

Strong to Extreme SW winds have built wind slabs low in lee areas. Prior to this wind, we received up to 150cm of fresh snow over the week (with freezing levels reaching 2000m near the end of the storm). This sits on a sun crust, wind crust or facets. Basal facets in shallow snowpack areas have been the cause of some large avalanches recently.

Avalanche Summary

No recent avalanche activity has been observed or reported. Thursday/Fridays warming and snow/rain event triggered a widespread natural avalanche cycle, 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.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Strong-Extreme Westerly winds are depositing snow further down slope than one might expect. Be cautious as you transition into wind affected snow.

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

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

While deep Storm Slabs from last weeks heavy snowfall have gained some strength over the past few days, this weeks warm temperatures may increase the likelyhood of triggering them.

Travel early before the heat of the day, and avoid big slopes.Avoid paths that have not avalanched recently.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - 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.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Feb 15th, 2017 4:00PM