Avalanche Forecast

Issued: Feb 3rd, 2018 5:33PM

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

mgrist, Avalanche Canada

Kootenay Boundary.

Snowfall amounts are uncertain in the current weather pattern. Danger ratings are based on the higher forecast amounts of snow. If you see more than 30cm of new snow on Sunday it's best to avoid all avalanche terrain, free from overhead hazard.

Summary

Confidence

Low - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Sunday: 5-20cm of new snow / Moderate to strong (south) west winds / Freezing level near 1000mMonday: Isolated flurries (5cm possible) / Light westerly winds / Freezing level around 1400mTuesday: Flurries (5-10 cm possible) / Moderate west winds / Freezing level around 1200mNote: Confidence is low for forecast wind values and precipitation amounts on Sunday.

Avalanche Summary

On Friday, natural and human triggered storm slab avalanches were reported, especially in areas which saw locally intense snowfall amounts in the afternoon. Looking forward, expect newly formed wind slabs and the persistent slabs beneath them to remain reactive to human triggers with the potential for very large and destructive avalanches.

Snowpack Summary

Storm snow totals over the past two days are approximately 15-30cm. Winds were gusting moderate at times and created fresh wind slabs on a wide range of aspects at upper elevations. Critical instabilities are buried well below the surface: See this video for a summary of conditions near Nelson. A mixture of weak surface hoar and/or a crust from mid-January is buried beneath all the storm snow at 80-110cm deep. Numerous recent avalanches to size 2.5 have been reported on this layer and large, destructive avalanches at this interface remain a concern.Below this layer lies a second crust/surface hoar interface buried early-January that is now 110-130 cm deep. Several recent avalanches have stepped down to this layer.The mid-December surface hoar layer is buried 120-150 cm below the surface. This layer has continued to produce step down releases and "sudden" test results. It is most pronounced at tree line, but is also present below tree line .

Problems

Storm Slabs

The current weather pattern is not handled well by forecast models and storm snow totals have large uncertainty associated with them.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Dial back your terrain choices if you are seeing more than 25cm of new snow.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

The snowpack is complex and continues to produce very large avalanches on several weak layers buried 80 to 150 cm below the surface. Moderate-angled, simple terrain selection remains critical to safe mountain travel.

Good day to make conservative terrain choices.Be mindful that deep instabilities are still present and have produced recent large avalanches.Minimize overhead exposure; avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Feb 4th, 2018 2:00PM