Avalanche Forecast

Issued: Feb 6th, 2016 8:53AM

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.

jlammers, Avalanche Canada

Northwest Coastal.

Stormy conditions are elevating the avalanche danger to HIGH. Strong winds, rising freezing levels and heavy precipitation may trigger very large avalanches.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

On Sunday and Monday another wet, warm and windy storm will impact the region. Expect between 30-50mm of precipitation per 24 hour period with freezing levels climbing from 500m on Sunday morning to 1800m by Monday afternoon. On Tuesday, expect a mix of sun and cloud with the freezing level shooting up to 2500m. Ridgetop winds should remain strong to extreme from the southwest for the forecast period.

Avalanche Summary

Avalanche observations have been quite limited in recent days, mostly due to stormy weather. However, in the mountains near Stewart fairly widespread storm slab activity (mostly size 2 with a few to size 3) was reported on Friday. Looking forward, a juicy storm on Sunday and Monday is forecast to promote widespread storm slab avalanches. New snow will also increase the likelihood of destructive persistent slab avalanches. At elevations where rain falls loose wet and wet slab avalanches are also likely.

Snowpack Summary

A warm, wet and windy storm forecast for Sunday will create deep new storm slabs throughout the day adding to an ongoing storm slab problem. Freezing levels are expected to rise dramatically throughout Sunday leaving surfaces at treeline and below saturated by the afternoon. Recent storm accumulations may be especially touchy as they are sitting on a new surface hoar layer that was buried on February 3rd. The January 9th surface hoar/facet layer is down 70-150 cm in most places, and remains a concern on all aspects and elevations, especially with heavy and/or thin-spot triggers. Around the same depth you may also find a surface hoar/facet interface from around New Years. There continues to be a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem; however, warming and forecast heavy storm loading will increase the likelihood of triggering these layers where they still exist. A conservative approach to mountain travel is still required.

Problems

Storm Slabs

A potent storm forecast for Sunday and Monday will form deep and reactive storm slabs. Storm slabs may be extra touchy due to recently buried surface hoar.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Heavy storm loading from snow or rain may trigger deeply buried persistent weak layers resulting in very large avalanches with wide propagations.

Be careful with low angle slopes that may not normally be a concern.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Loose Wet

Heavy rain forecast for Sunday and Monday will promote loose wet avalanche activity in steep lower elevation terrain. Destructive wet slab avalanches are also possible.

Stick to non-avalanche terrain or small features with limited consequence.>Be cautious of wet sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Feb 7th, 2016 2:00PM