Avalanche Forecast

Issued: Feb 7th, 2016 8:18AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Rain and rising freezing levels over the next few days will weaken the snowpack and increase the Avalanche Danger.

Summary

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

On Monday, expect 10-15mm of precipitation with freezing levels climbing from 1600m to 1900m throughout the day. On Tuesday the region will see a mix of sun and cloud with freezing levels shooting to 2800m. Light snowfall is forecast for Wednesday. Ridgetop winds are forecast to remain strong from the southwest for the entire forecast period.

Avalanche Summary

On Saturday explosives control in the Stewart and Ningunsaw areas produced deep persistent and storm slab avalanches in the size 2.5-3 range. While most avalanches observed failed within recent storm layers, a few failed on basal facets in shallow snowpack parts of the region. There was also a recent size 3 natural persistent slab avalanche north of Stewart. This avalanche failed on the January 9th surface hoar.Closer to Terrace, a few recent storm slab avalanches to size 3 were observed between 1200 and 1700m. A skier also triggered a size 1.5 wind slab avalanche on a southwest aspect at 1450m. The skier was not injured.I'm sure there was a decent round of storm slab activity on Sunday in response to new snow and wind.

Snowpack Summary

On Monday continued warm, wet and windy conditions will add mass to recently formed storm slabs. Freezing levels are expected to rise dramatically 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, 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, forecast rain and warm temperatures will increase the likelihood of triggering these layers where they still exist. A conservative approach to mountain travel is still required.

Problems

Storm Slabs

Ongoing storm accumulations will likely remain sensitive to human triggering on Monday. Watch for increased reactivity in high elevation lee terrain.

Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Loading from new snow and rain will increase the likelihood of waking up destructive persistent weak layers at all elevation bands.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Loose Wet

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Feb 8th, 2016 2:00PM