Avalanche Forecast

Issued: Jan 27th, 2012 8:20AM

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

ghelgeson, Avalanche Canada

Purcells.

The snowpack in the Purcells is quite spacially variable and complex. Carefully evaluate each slope before committing to it.

Summary

Confidence

Fair - Freezing levels are uncertain on Monday

Weather Forecast

A significant storm system enters the region Saturday evening bringing 30 - 40 cm of new snow. This system exits the region Sunday as freezing levels climb to 1400 m. Average seasonal temperatures return Monday while a weak ridge of high pressure builds into the forecast area.

Avalanche Summary

Avalanche obs are also quite spatially variable. Control work in the Dogtooth's produced avalanches to Size 3 running on basal facets with small loads. Just a bit south of Golden control work with large loads produced very little activity. Wind effected terrain in the region went through a natural avalanche cycle to size 2.5 on Thursday.

Snowpack Summary

The Purcell's are one of the more complex & variable snowpacks in the province right now.The region has received 70 - 130 cm of storm snow in the last week. A few shears are persisting in the storm snow, but these are healing. Winds have been predominantly out of the W, SW, but some stations have reported NW winds in the last 24 hours. I`ve received obs of surface snow that is untouched by winds, and other obs where winds have produced a wind slab avalanche cycle. It`s tough to put a pattern on what`s happening out there. I suspect it`s highly drainage dependent at the moment.The mid-December surface hoar/facet combo is down around 70 cm on the E side of the range & 230 cm on the west side. I suspect it's still susceptible to human triggering in the shallow snowpack areas.

Problems

Wind Slabs

Watch for wind slab in exposed areas at all three elevation bands as wind continues to redistribute storm snow into soft slabs.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Storm Slabs

South of Golden, storm snow totals are near 100 cm & a few different shears can be found in the new snow. You're most likely to trigger a storm slab in steep unsupported terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

Two layers to watch: 1. Buried surface hoar, most likely triggered on steep, unsupported slopes amongst the trees. 2. Basal facets, triggerable from thin snowpack areas or by a heavy load (cornice fall, airborne sled).

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

4 - 7

Valid until: Jan 28th, 2012 8:00AM