Purcells

A nasty weak layer is coming into play and it's all about the depth of new snow. If 15 cm or less adds up on the old surface, expect reactive new wind slabs in leeward pockets. If totals are closer to 20 cm or more, treat danger as CONSIDERABLE and dial terrain choices way back.

Thursday night: Cloudy with continuing scattered flurries bringing another 5-10 cm of new snow. Light to moderate south or southwest winds.

Friday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Alpine high temperatures around -9.

Saturday: Cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds, increasing over the day and overnight. Alpine high temperatures around -9.

Sunday: Cloudy with continuing scattered flurries bringing up to 5 cm of new snow, increasing a bit overnight. Light south winds, becoming strong in the alpine. Alpine high temperatures around -6.

On Thursday in the Golden area, about 10 cm of new snow coupled with easterly wind led to the formation of small but reactive new wind slabs and cornice growth. We're still lacking observations from elsewhere in the region, but it's safe to assume similar, if not more dangerous conditions exist in other areas with similar or greater new snow accumulations.

We're continuing to track a layer of surface hoar from early January. Two MIN reports (MIN report 1; MIN report 2) from north of the region in Hope Creek report human-triggered slab activity from January 20. This MIN report from the Quartz zone (from Jan 14) shows a reactive layer of Jan 11th surface hoar on north-facing slopes near treeline. Concern for this layer is increasing in line with loading from new snow and increased avalanche activity in shallower snowpack layers.

A variable 15 to 30 cm of new snow is expected to have accumulated in the region by Friday morning, with heavier amounts limited to the west of the region. The new snow has buried a layer of surface hoar recently reported in sheltered areas of the region. In many areas gusty winds over the weekend damaged these crystals in exposed upper elevations. 

Aside from this weak surface crystal, the new snow has buried a variety of surfaces including scoured and pressed surfaces in exposed terrain as well as more variable wind affected and faceted snow in sheltered terrain. A thin sun crust may be found on steep solar aspects.

A weak of layer of surface hoar from Jan 11th is down 15-70cm. In recent snowpack tests at treeline elevations near Golden this layer produced sudden results. This persistent weak layer is most suspect in sheltered, open slopes at treeline and warrants slope-specific investigation if you're travelling in the north of the region. Concern for this problem is increasing in line with loading from new snow and increased avalanche activity in shallower snowpack layers.

Two deeper layers of surface hoar from December 13th and December 7th may still be found down 100-150 cm. The Dec 7th weak layer consists of a combination of decomposing surface hoar with a crust and faceted snow. Avalanche activity on these persistent weak layers has dwindled for a couple of weeks, with snowpack tests results trending to resistant and unreactive. 

The lower snowpack is characterized by a notable rain crust from early November that is surrounded by a weak layer of sugary facets. It may still be possible to trigger with large loads in steep, shallow, rocky areas with a thin to thick snowpack.

• Make observations and assess conditions continually as you travel.
• Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.