Avalanche Forecast

Issued: Feb 15th, 2016 8:23AM

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

jlammers, Avalanche Canada

Purcells.

A recent size 3 persistent slab avalanche near Golden is a clear indication that deeply buried weaknesses cannot be trusted. Extra caution is required in the north of the region near Golden.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

TONIGHT: 5-10cm of snow / Strong southwest winds / Freezing level at 1500m TUESDAY: Mix of sun and cloud / Light to moderate southwest winds / Freezing level at 1800m WEDNESDAY: Light flurries / Light to moderate southwest winds / Freezing level at 1800m THURSDAY: 5-15cm of snow / Moderate southwest winds / Freezing level at 1500m

Avalanche Summary

On Monday naturally triggered wind slabs to size 2 were observed in the Golden area. On the same day, a size 3 naturally triggered persistent slab avalanche was also noted in Canyon Creek (Golden Backcountry). The avalanche is thought to have been triggering by a wind slab in motion stepping down to the early January persistent weak layer. Increasing southwest winds and new snow on Monday night will spark a new round of wind slab activity in higher elevation lee terrain. Periods of sun on Tuesday may also promote loose wet avalanche activity in steep sun-exposed terrain, especially in spots where new snow is exposed to solar radiation for the first time.

Snowpack Summary

On Monday night, generally light amounts of new snow are expected to fall, and strong southwest winds are expected to form new wind slabs in lee features at treeline and in the alpine. The new snow will overlie wind slabs which formed over the past few days. About 15-40 cm below the surface, you'll likely find a melt freeze crust which exists in most places except for in high elevation shaded terrain. In general there seems to be a reasonable bond between the crust and the overlying snow. I'd still keep an eye on this interface as it has become reactive on some features. The early January surface hoar/ facet layer is typically down 70-120 cm. Sporadic yet destructive avalanche activity continues on this persistent weak layer. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Problems

Wind Slabs

New wind slabs are expected to form on Monday night in response to light amounts of new snow and wind. Watch for triggering in the lee of ridgecrests at treeline and in the alpine.

Travel on ridges to avoid freshly wind loaded features. >Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A recent size 3 persistent slab avalanche near Golden is a clear indication that deeply buried weaknesses cannot be trusted. Extra caution is required in the north of the region near Golden.

Be cautious around open slopes and convex rolls at and below treeline where buried surface hoar may be preserved. Big alpine features are also suspect.>Avoid thin, rocky or sparsely-treed slopes.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 5

Loose Wet

Recent storm accumulations may react as a loose wet avalanche in steep, sun-exposed terrain. Warming may also trigger destructive cornice falls. Be extra cautious if the sun makes an appearance on Tuesday.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 16th, 2016 2:00PM