Avalanche Forecast

Issued: Jan 14th, 2014 8:19AM

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 Friday

Weather Forecast

Synopsis: The interior of BC will come under the influence of a strong ridge of high pressure and warm temperatures for the next few days.Overnight: Light precipitation, winds changing to mod to strong W, freezing levels at valley bottom.Wednesday: Some sunny periods, winds moderate to strong from the west, freezing levels to 1400 M in parts of the forecast area.Thursday: No precipitation in the forecast, sunny periods,. light winds at ridge tops freezing level rises to 1800m.Friday: No Precipitation , sunny periods, winds light to moderate from the W-NW at ridge tops, freezing levels may rise to 2300m in some 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. Reports indicate that the storm snow has not yet bonded to the older layers and wind and storm slabs are easily triggered and may propagate quite far. 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 10 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. Give the snow pack a chance to bond-up before riding on big lines.

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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Jan 15th, 2014 2:00PM