Avalanche Forecast

Issued: Apr 15th, 2017 5:35PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Sun will be the main driver of avalanche danger. Be cautious of steep sunny slopes, or of exposure to cornices that may be sneakily catching sun from behind.

Summary

Weather Forecast

Sunday: Mainly Sunny. Westerlies easing to Calm. Freezing Level rising to 2000m. Treeline Low -6.5, High -1.Monday: Mainly cloudy. Light Westerlies/light flurries developing. Freezing Level 2200m. Treeline Low -1, High 0.5Tuesday: Cloudy, light flurries. Moderate Westerly winds. Freezing Level 2200m. Treeline Low -2, High 0.5.

Snowpack Summary

15cm of storm snow has trickled in over three days, creating storm slab pockets on slopes immediate lee to accompanying Strong SW winds. These sit on a widespread crust that formed after warm temperatures one week ago. Beneath is a well settled spring snowpack; however, facets still make up the bottom of the snowpack in some high Alpine areas.

Avalanche Summary

On Saturday, a recent cornice fall avalanche from an Alpine ridge was observed, which had triggered a small storm slab from a steep, unsupported lee slope. (This amounted to a Small avalanche - Size 1.5) On Friday, Numerous Small, Loose Wet avalanches occurred, as rain soaked fresh new snow that sat on a crust.

Confidence

Timing or intensity of solar radiation is uncertain on Monday

Problems

Storm Slabs

Storm Slab pockets exist lee to West and SW winds, especially immediately behind ridge crests, outcrops, and islands of trees ("immediate lees"). It is possible a person or solar radiation could trigger these. This problem will lessen over time.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

Cornices growth has continued. Periods of intense solar radiation will increase the chance of these failing naturally. Of course, they are most likely to break if walked upon.

Give cornices a wide berth when traveling on ridges.Do not travel on slopes that are exposed to cornices overhead.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

Loose Wet avalanches are possible on steep slopes on SUNDAY, as strong April Sun warms recent, soft surface snow. Expect this to be most pronounced were the most new snow lies: Easterly aspects/upper elevations in the Western portions of the park.

Use extra caution on solar slopes or if the snow is moist or wet.Minimize exposure to terrain traps where the consequences of a small avalanche could be serious.

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

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Apr 18th, 2017 4:00PM