Avalanche Forecast

Issued: Nov 25th, 2014 8:50AM

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

South Columbia.

Stormy weather will drive avalanche danger up this week. It's a good time for riding low angle slopes and avoiding overhead exposure.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A warm front will move over the southern part of the province midday Wednesday resulting in mild temperatures and moderate to heavy precipitation. This will persist through Thursday before an Arctic front pushes down from the north on Friday. The boundary of the warm air on Wednesday and Thursday currently sits in the middle of the S Columbia region so there is a lot of uncertainty regarding freezing levels. Southern parts of the region may see a mix of rain and snow whereas the north may be primarily snow.Tues. Night/Wednesday: Precipitation 10-20mm, freezing levels starting around 500m rising to around 2000m late-Wednesday, ridgetop wind moderate SW-WWeds. Night: Precipitation 10-20mm, ridgetop wind moderate SW-WThursday: Precipitation 10-15mm, freezing levels around 2000m in the south, possibly lower in the north, ridgetop wind strong SWFriday: A mix of sun and cloud, snow flurries possible, freezing level valley bottom, ridgetop wind light variable

Avalanche Summary

Natural avalanche activity up to size 2 was reported in Glacier National Park on the weekend. On Monday, explosive control at a ski area produced widespread size 2 storm slabs. On Tuesday, Glacier National Park reported numerous natural avalanches up to size 3. Observations are still very limited but it is expected that avalanche activity is occurring throughout the region. As new snow continues to accumulate, natural avalanche activity is expected to continue and the size of these avalanches will continue to increase.

Snowpack Summary

This is an estimate of what the snowpack may look like based of a few observations and previous weather. If you plan on riding in avalanche terrain be sure to supplement this with your own observations and please pass along any data you collect (forecaster@avalanche.ca). Around 70-100cm of recent storm snow sits on the mid-November drought layer (facets, surface hoar, and/or a sun crust on steep southerly slopes). Below this is 20-30 cm of old snow, which is probably quite weak and facetted (sugary). A thick rain crust which formed a few weeks ago is now down 90cm or more. The average snowpack depth at treeline is now around 1-1.5m. Recent strong and variable winds have probably created dense wind slabs in exposed terrain and resulted in variable snow distribution. 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 developing storm slab sits on a touchy weak layer and is expected to become very reactive with additional storm loading. Recent wind loading has created wind slabs in leeward features which are expected to be very touchy.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be alert to conditions that change with elevation.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

3 - 6

Loose Dry

Be cautious of loose sluffing from steep terrain as new snowfall continues. Forecast rain at lower elevations may result in loose wet activity.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Nov 26th, 2014 2:00PM