Avalanche Forecast

Issued: Nov 26th, 2014 9:07AM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Loose Dry.

rbuhler, Avalanche Canada

Purcells.

Winter storm conditions have produced a storm slab which sits on a touchy weak layer. Now is a good time to avoid avalanche terrain and stick to low angle slopes.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A warm, moist Pacific storm will continue to bring heavy precipitation to the southern interior on Thursday. The southern Purcells can expect to see a substantial rise in the freezing level on Thursday whereas the north of the region may stay cool. An Arctic high pressure is expected to arrive on Friday morning bringing cold, sunny conditions for the weekend. Weds. Night/Thursday: Precipitation 10-20mm, freezing level around 2000m, lower in the north, ridgetop wind strong SW Thurs. Night: Precipitation 5-10mm, ridgetop wind strong SWFriday: A mix of sun and cloud, light flurries possible, freezing level valley bottom, ridgetop wind easing during the daySaturday: A mix of sun and cloud, treeline temperature around -15C, ridgetop wind light N

Avalanche Summary

There are no new field reports from the Purcells. Recent reports from Rogers Pass include widespread natural activity up to size 3. The storm snow in Purcells may not yet be enough for widespread natural activity but the warming on Thursday should produce some natural activity, especially in wind loaded areas. Please help us improve this forecast and send observations to forecaster@avalanche.ca.

Snowpack Summary

This is an estimate of what the snowpack may look like based on a few old observations and previous weather. If you plan on heading into the mountains be sure to supplement this with your own observations and please pass along any data you collect (forecaster@avalanche.ca).Around 30-50 cm of recent storm snow has fallen in the past few days. This new snow may be sitting on a layer of surface hoar, facets, and/or a sun crust (similar to the South Columbia). Below this you will likely find a 15-25cm thick layer of sugary facets, which is sitting on a solid rain crust from early November. Recent strong and variable winds have probably created dense wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. At lower elevations, expect travel to be difficult and potentially hazardous as many early season hazards are exposed or lightly buried (stumps, logs, rocks, open creeks, etc).

Problems

Storm Slabs

The storm slab sits on a touchy weak layer and is expected to become reactive with additional storm loading and warming. Recent wind loading has created wind slabs in leeward features which are expected to be very touchy.

Choose conservative lines and watch for clues of instability.>Avoid freshly wind loaded features.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 4

Loose Dry

Be cautious of loose sluffing from steep terrain as new snowfall continues. Rain at lower elevations may cause loose wet activity.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Nov 27th, 2014 2:00PM