Avalanche Forecast

Issued: Nov 27th, 2014 8:40AM

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

Avalanche Canada rbuhler, Avalanche Canada

A Special Avalanche Warning has been issued for this weekend. A persistent slab sitting on a touchy weak layer will continue to produce large avalanches for several days after the storm ends.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

The warm, moist storm system will continue to produce precipitation on Thursday night and early Friday morning. An Arctic high pressure system will move into the region sometime during the day on Friday. Temperatures are expected to drop substantially on Saturday and persist for a few days.Thurs. night/Fri. morning: Precipitation 10-15mm, freezing level around 2000m, strong SW alpine wind. Friday afternoon: Precipitation tapering off, freezing level falling to valley bottom, alpine winds easing. Saturday: A mix of sun and cloud, snow flurries possible, treeline temperature around -15C, light N alpine wind.Sunday: Mostly sunny, treeline temperature around -20C, light N alpine wind.

Avalanche Summary

A report from the Invermere area suggests widespread natural activity up to size 2 on all aspects above 1800m.  Observations from other parts of the region are limited.  If you are out in the mountains and observe activity, please send your 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 40-60 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

An icon showing Storm Slabs
The storm slab sits on a touchy weak layer and has the potential to produce large natural avalanches. Strong alpine winds have loaded leeward features in exposed terrain creating touchy wind slabs.
Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Avoid freshly wind loaded features.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 4

Valid until: Nov 28th, 2014 2:00PM

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