Avalanche Forecast

Issued: Mar 17th, 2017 3:57PM

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

shorton, Avalanche Canada

Kootenay Boundary.

Saturday's storm has all of the the ingredients for large avalanches. Travel in avalanche terrain is not recommended.

Summary

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Storm begins with 10-20 cm, strong southwest winds, and freezing level around 1500 m.SATURDAY: Storm continues with another 15-30 cm (and possibly more around Kootenay Pass), strong to extreme southwest winds, freezing level climbing up to 2000 m.SUNDAY: Clearing skies following the storm as alpine temperatures drop to around -8 C, light west winds.MONDAY: Sunny with cloudy periods, alpine temperatures around -5 C, light winds.

Avalanche Summary

Reports continue to come in about a widespread natural avalanche cycle that occurred during last week's rain event. Avalanches were reported on all aspects and elevations, many up to size 3 and over 100 cm deep. A few large cornice failures occurred as well. Several avalanches in the Bonningtons were reported to step down to the late-February interface, and similar step downs likely occurred in other areas as well. Avalanches at lower elevations entrained significant amounts of wet snow. Activity tapered off on Thursday, but the snowpack has not yet had to time to adjust to the heavy loading and warming.On Saturday, heavy precipitation and warming will result in another round of large natural avalanches with the potential to step down to deep weak layers.

Snowpack Summary

A juicy storm will start as snow on Friday night and switch to rain in the morning to form very touchy storm slabs at high elevations and unstable wet snow at lower elevations. Extreme southwest winds will have a dramatic effect on all exposed terrain and likely form touchy cornices. The storm is burying a rain crust that exists up to about 2200 m. Several deeper weak layers were tested during last week's storm including the late-February facet / surface hoar interface (70-120 cm deep), the mid-February crust (90-130 cm deep), and basal facets in shallow snowpack areas. These layers may remain reactive with additional loading and warming.

Problems

Storm Slabs

Heavy amounts of new snow and warming will form very touchy storms slabs and widespread natural activity. Extreme winds and cornices will add to the danger.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.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 - 3

Persistent Slabs

The storm will also create the potential for very large avalanches on buried persistent weak layers. Smaller avalanches or cornices are likely triggers.

If triggered, smaller avalanches may step down to deeper layers resulting in very large avalanches.Maintain constant awareness of overhead hazards.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Loose Wet

Rain at lower elevations will likely produce wet snow avalanches in steep terrain, including forested areas.

If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 18th, 2017 2:00PM