Avalanche Forecast

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

The forecast period is marked by very little new snow and increasing wind through Saturday night.

THURSDAY NIGHT: Freezing level at valley bottom, moderate to strong south/southwest wind, potential for a trace of new snow by Friday morning.

FRIDAY: Broken cloud cover, freezing level near valley bottom, moderate to strong west/northwest wind, 1 to 5 cm of snow possible during the day.

SATURDAY: Scattered cloud cover, freezing level at valley bottom, light variable wind at most elevations, moderate to strong west/northwest wind in high elevation alpine terrain, no significant precipitation expected.

SUNDAY: Scattered cloud cover, freezing level at valley bottom, light variable wind, no significant precipitation expected.

The Purcells continue to produce avalanche activity that is simultaneously impressive and scary. It happened again on Wednesday when a group of skiers remote triggered a size 3 deep persistent slab avalanche in the Golden backcountry. The avalanche occurred on a southwest through northwest facing terrain feature around 2200 m. The crown was up to a 100 cm in depth. The group that remote triggered the avalanche also observed numerous large avalanches that failed naturally and went to ground.

Control work in the central portion of the region Wednesday produced persistent slab avalanches to size 3 on north facing terrain around 2500 m.

It's been like this since last Friday: 

On Tuesday a natural size 2.5 avalanche began on a north facing feature at 2200 m before ending up in a creek. Numerous size 3.5 avalanches were triggered by explosive control work in the central portion of the region on all aspects around 2500 m, crown depths were up to 200 cm.

On Monday control work produced very large (size 2.5 to 3.5) avalanches on a variety of aspects in the alpine. Some of these avalanches ran beyond historical norms and created new trim lines where there were once trees.

Avalanche activity was widespread Friday through Sunday with reports of natural, human and explosive triggered avalanches up to size 4.

The Purcells received 60-120 cm from last weekend's big storm which is settling into a deep persistent slab. There may be two layers of surface hoar buried between 70-180 cm below the surface.

The base of the snowpack is astonishingly weak, far more so than in the average season. The weak interface at the base is widespread across aspects and elevation bands meaning it's almost everywhere. It consists of crust, facets and depth hoar. This weakness has been responsible for some spectacularly large and destructive avalanches recently.

• Conservative terrain selection is critical, choose only well supported, low consequence lines.
• Back off steep and aggressive lines, stick to simple terrain.
• Don't let the desire for deep powder pull you into high consequence terrain.
• Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.