Avalanche Forecast

Issued: Dec 20th, 2013 8:33AM

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

ghelgeson, Avalanche Canada

Northwest Coastal.

Rain falling on snow will rapidly increase the avalanche hazard. Saturday's ratings will quickly jump to Sunday's ratings if/when rain begins to fall on Saturday.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Synopsis: Saturday offers a short break in the action before another frontal wave crashes into the mountains of the North Coast Saturday evening. Precip continues through the day Sunday as freezing levels rise, possibly as high as 1500 2000m Sunday evening. All bets are off for Sunday night. The bulk of the precip has the potential to fall as rain. Stay tuned for more info!Saturday: Freezing Level: Valley Bottom Precip: 1/5mm - 2/10 cm Wind: Lht W/NWSunday: Freezing Level: 1800m Precip: 35-40mm snow/rain mixed Wind: Mod gusting Extreme, SWMonday: Freezing Level: 1100m Precip: 3/6mm 5/10cm Wind: Lht gusting Mod, W

Avalanche Summary

There wasn't much avalanche activity reported from Thursday, likely due to the cooler temperatures. I'm guessing that we'll see a fair amount of avalanche observations from Friday with all of the new storm snow. During the first half of the week numerous size 2-3 avalanches were running naturally and with explosive assistance throughout the region on all aspects with the bulk of the activity occurring on N - SE facing aspects.

Snowpack Summary

Total snowpack depth in the region ranges between 150 - 250cm. On December 20th the region picked up almost 50 cm of new snow that rests on a variety of old surface layers: old wind slabs, a crust that formed on Dec. 14 in some locations and even small grained surface hoar. This brings the total load of snow on the December 12 layer to 75 - 130 cm. December 12th is a surface hoar/facet combo formed during the early December cold snap which rests on old wind slabs and melt freeze crusts. Strong winds out of the South & West have been working overtime to redistribute storm snow from the past week into what is now a widespread wind slab problem at and above treeline.The mid pack is composed of various faceted layers and crusts. A significant crust/facet combo lingers near the base of the snowpack.

Problems

Storm Slabs

Friday's storm snow rests on a mixed bag of old surfaces and should remain quite sensitive to human triggering Saturday. Be advised that any rain will likely result in a radical spike in avalanche activity.

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.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Deep Persistent Slabs

As the mid & lower snowpack adjusts to it's new snow load, large destructive avalanches may be susceptible to triggering by both humans and smaller avalanches. This problem will be further exacerbated by rapidly warming temps and rainfall on Sunday.

Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid shallow snowpack areas where triggering is more likely.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 6

Valid until: Dec 21st, 2013 2:00PM