Avalanche Forecast

Issued: Feb 17th, 2017 5:08PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Deep Persistent Slabs and Wind Slabs.

shorton, Avalanche Canada

South Rockies.

Danger will remain elevated throughout the weekend. The lingering possibility of deep persistent slab avalanches warrants extra caution around big open slopes.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

SATURDAY: Cloudy with light flurries starting in the afternoon and 5-10 cm of new snow overnight, light to moderate south winds, freezing level around 1300 m.SUNDAY: Cloudy with isolated flurries, moderate southwest winds, freezing level around 1300 m.MONDAY: Storm starting midday with up to 5 cm of new snow by the afternoon, strong southwest winds, freezing level around 1700 m.

Avalanche Summary

Recent avalanche reports in the region include size 1-2 loose wet avalanches in rain soaked snow at lower elevations. On Thursday, a small slab in Waterton stepped down in a shallow snowpack area below a cliff to release a size 2 deep persistent slab avalanche. Earlier in the week, a few size 2 solar-triggered persistent slab avalanches were observed in the Elkford area.For the weekend, watch for reactive wind slabs at higher elevations. Also keep in mind that the deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around and below large open slopes.

Snowpack Summary

5-20 cm of new wind affected snow can be found above 1800 m, while lower elevations will have a combination of moist snow and rain crusts as freezing levels fluctuate. Moderate southwest winds have redistributed the new snow into reactive wind slabs in exposed terrain. Beneath the new snow, you'll find a mix of hard old wind slabs, melt-freeze crusts, and moist snow from the recent warm spell. The midpack consists of 50-100 cm of settled snow from last weeks storm. In deep snowpack areas, the lower snowpack appear to be well settled with only isolated concerns about the mid-December facet layer which comprises the bottom third of the snowpack. In shallow snowpack areas, this layer is weak and faceted. Watch this video from the South Rockies field team for some recent test results on this layer.

Problems

Deep Persistent Slabs

A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction and areas with thin variable snow cover.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Watch for fresh and reactive wind slabs in exposed high elevation terrain.

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.Use caution above cliffs where small avalanches may have severe consequences.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

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