Avalanche Forecast

Issued: Dec 30th, 2015 9:01AM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs, Persistent Slabs and Loose Dry.

rbuhler, Avalanche Canada

Purcells.

Riding conditions are excellent right now but isolated problems still exist. Soft wind slabs may still be lingering around ridge crests in the alpine. Sluffing can be expected on steep sun-exposed slopes during the heat of the afternoon.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

High pressure is the dominant feature for the foreseeable future. In the alpine, sunny conditions are expected for the next few days but most of the valleys will likely to be under valley fog. On Thursday, treeline temperatures will be around -5C with colder temperatures in the valleys. Alpine winds may be moderate from NE in the morning but should ease during the day. On Friday, a layer of above freezing air is expected to invade the alpine. By Saturday, temperatures could be a few degrees above zero from around 2000m to 3000m elevation. On both Friday and Saturday, alpine winds should be light and above the valley fog the conditions should be clear and sunny.

Avalanche Summary

Over the last few days, several small loose dry avalanches and one size 1.5 wind slab have been observed. Persistent slabs were last triggered about a week ago. Unfortunately these types of problems don't heal quickly, so they remain on our radar. This problem may wake up with the upcoming warm temperatures in the alpine.Â Progressive warming in the alpine with ongoing sunny conditions should result in ongoing loose natural avalanches from south-facing slopes and by the weekend may create slab properties within the recent storm snow.

Snowpack Summary

20-30 cm of low-density snow typically overlies a well-settled mid and lower snowpack. Surface hoar and near-surface facets may be mingled within the upper few cm. Storm slab properties may change and become more cohesive as the alpine gets some sun and warmer temperatures. Wind slabs, found in the lee of ridges and ribs, are still reactive in some spots and healing in others.Â A weak layer which was buried in early December is down about 40-100 cm. At and below treeline, it mainly consists of large surface hoar. At higher elevations, it consists of a sun crust, facets, and/or small surface hoar. This layer is still reactive in some snowpack tests and has produced at least one human-triggered avalanche in the last week. The persistent slab is a low probability, high consequence problem. Below this layer, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

Wind slabs may still be lurking behind ridges and ribs. Winds have recently changed directions so the problem could exist on either side of a ridge.

Use ridges or ribs to avoid pockets of wind loaded snow. >Be cautious as you transition into wind affected terrain. >

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

A weak layer buried about 40-100 cm down remains reactive in snowpack tests in some areas. It has produced avalanches within the last week and could wake-up with the upcoming warm temperatures in the alpine.

Conditions are greatly improved, but be mindful that persistent weak layers are still present. >Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

2 - 4

Loose Dry

As the temperatures in the alpine continue to rise, the sun will pack more punch. Loose avalanche activity is expected to continue from steep, rocky, sun-exposed slopes. The volume of dry snow could push you around.

Minimize exposure to steep sun exposed slopes when the solar radiation is strong. >Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >Be aware of party members below you that may be exposed to your sluffs. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 31st, 2015 2:00PM