Avalanche Forecast

Issued: Jan 13th, 2014 8:30AM

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

bcorrigan, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Freezing levels are uncertain on Thursday

Weather Forecast

Overnight : Flurries with trace amounts of precipitation, winds from the west at ridge top 30 to 60 km/h, freezing level rising to 700m.Monday: Flurries with trace amounts of precipitation, strong winds from the W-NW at ridge top gusting to 100 km/h, freezing level rising to 1200 M.Tuesday: No Precipitation in the forecast, moderate to strong winds from the west, freezing levels may rise to 1500m in parts of the forecast area.Wednesday: No Precipitation in the forecast, moderate winds from the west, freezing level should come down to 1200m in parts of the forecast area.

Avalanche Summary

There have been a number close calls with large avalanches in the north of this region in the last three weeks. Check out the incident database for more details. Recent reports of numerous skier controlled size 1 to 2's days indicate the severity of the new snow and wind loaded snow instability. There is a very real possibility that a small avalanche could "step down" to the weak facetted layer at the base of the snowpack and produce a large destructive avalanche.

Snowpack Summary

Amounts of new snow are highly variable over the length of the forecast area, with the western parts of the range getting as much as 40 cm in the past 24 hrs, The eastern and southern parts have received 15 to 20. The new snow sits on a variety of snow surfaces including older wind slabs and a soft layer of facetted snow and/or surface hoar from earlier in January. All of this is sitting on top of older wind slabs and a couple of persistent weak layers in the upper meter of the relatively thin snowpack. A mid December surface hoar is buried around 30-90 cm. The early December facet/crust combo is buried down 50-150 cm. Both interfaces give variable results with snowpack tests, but professional operators are treating them with caution.A big concern, especially in the northern part of the region is a layer of weak sugary depth hoar crystals at the base of the snowpack that lie above a crust from early October. Several large avalanches in the last weeks have been attributed to failures at this layer. Wide propagations on relatively gentle terrain have been noted, and an alarming tendency for seemingly disconnected slopes to propagate over a wide area and produce large avalanche.

Problems

Storm Slabs

Recent snowfall accompanied by strong winds and warm temperatures have created the high hazard in the mountains. Use caution when venturing into or near avalanche terrain.

Stick to simple terrain and be aware of what is above you at all times.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid all avalanche terrain.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 5

Persistent Slabs

Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.Choose well supported terrain without convexities.Be aware of thin areas that may propagate to deeper instabilities.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Deep Persistent Slabs

Large human triggered avalanches have occurred after riders found stable results from snowpack testing. Large features, especially in the north of the region, should be avoided at this time.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Jan 14th, 2014 2:00PM