Avalanche Forecast Northwest Coastal

Date Issued: Valid Until:

Avalanche Canada ghelgeson, Avalanche Canada

Avalanche Forecast

Fri Mar. 15th ยท 5:52PM

Alpine

Danger Ratings High

Treeline

Danger Ratings High

Below Treeline

Danger Ratings Considerable

Problems

Storm Slabs Storm Slabs
Persistent Slabs Persistent Slabs

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Considerable

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Considerable
Strong to extreme wind and new snowfall are expected to drive a natural avalanche cycle. We cannot trust the weak layers formed during the drought with this kind of loading, so rein the terrain choices way in and steer clear of overhead hazard.

Confidence

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

Weather Forecast

A severe wind event is expected to impact the region Saturday before a significant warm up begins on Sunday. Next week looks to be very warm with the freezing level approaching 3000 m by Tuesday. Unfortunately, very little overnight re-freeze is expected during the warm spell.FRIDAY NIGHT: Freezing level around 600 m, moderate to strong southwest wind, 2 to 8 cm of snow.SATURDAY: Overcast, freezing level rising to 1000 m in the afternoon, strong to extreme southwest wind, 5 to 15 cm of snow. SUNDAY: Broken cloud cover, moderate to strong south/southwest wind, freezing level approaching 2000 m, a few mm of precipitation possible.MONDAY: Scattered cloud cover, moderate to strong south/southwest wind, freezing level approaching 2500 m, no significant precipitation expected.

Avalanche Summary

Recent avalanches can be divided into two classes -- light triggers and large triggers. For light triggers there are reports of wind and storm slabs up to size 2.5 on northerly aspects in northern areas . Throughout the region there were reports of a solar triggered cycle up to size 2 on solar aspects. Closer to Terrace there was a report of small soft slab triggered by a skier, a wind slab cycle up to size 1.5 (due to some strong southerly winds), and some loose dry avalanches, possibly as large as size 2. Most recent avalanche activity was a result of larger triggers, namely explosives. Explosive tests and control resulted in mostly size 2 avalanches but in some inland areas in the east side of the region avalanches up to size 3.5 were triggered. Strong to extreme southwest wind Saturday combined with new storm snow is likely to initiate a natural avalanche cycle.

Snowpack Summary

Continued snowfall is adding to the 40-60 cm of previous storm snow. The recent snow is settling but is covering a wide variety of old snow surfaces: crusts on solar aspects, facets up high, and surface hoar in sheltered locations. Not much further below this storm snow interface is a second weak layer buried on February 19 made up of weak facets and surface hoar crystals. Recent avalanche activity was more or less equally split between these two layers.The lower snowpack is generally strong.

Problems

Storm Slabs

Storm Slabs

5 to 15 cm of new storm snow combined with strong to extreme southwest wind Saturday is likely to initiate a natural avalanche cycle that will be most pronounced in wind exposed features at and above treeline.

Avoid all avalanche terrain during periods of heavy loading from new snow and wind.Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.Continue to make conservative terrain choices and avoid overhead avalanche hazard.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

Persistent Slabs

Previous weaknesses in the upper snowpack (30 - 40 cm of sugary facets) may re-activate during Saturday's storm. A weak layer buried around 60 cm below the surface likely remains sensitive to triggering too.

Remote triggering is a concern, watch out for adjacent slopes.Storm or wind slabs may step down to deeper layers resulting in large avalanches.Avalanche hazard is expected to increase throughout the day, think carefully about your egress.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Unlikely

Expected Size

2 - 3