Avalanche Forecast

Issued: Mar 24th, 2018 3:48PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Loose Wet.

swerner, Avalanche Canada

Northwest Coastal.

Watch for whumphing and cracking below your feet and continue to make observations while gaining elevation towards alpine terrain. If the sun pokes out it may initiate a natural avalanche cycle in the recent storm snow.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Sunday: Mix of sun and cloud with snow amounts 2-5 cm. Ridgetop wind strong from the southwest. Alpine temperatures near -3 and freezing levels 800 m. Monday: Heavy snow expected 20-35 cm. Ridegtop winds strong from the southwest. Alpine temperatures near -1 and freezing levels 800 m. Tuesday: A mix of sun and cloud. Ridgetop wind light from the West. Freezing levels 800 m.

Avalanche Summary

On Saturday, the strong westerly winds were responsible for triggering a couple of wind slabs up to size 1.5 from north-easterly aspects in the alpine. On Friday and MIN reported a rider triggered wind slab avalanche size 1.5 from a southwesterly aspect. The person rode out of the avalanche and the crown was reportedly 35 cm deep. Friday also saw a natural cycle up to size 2.5 in the recent storm snow.

Snowpack Summary

Up to 30 cm of new snow overlies a plethora of old snow surfaces including the March 9th and 19th surface hoar existing on high northerly aspects and a melt-freeze crust basically on all aspects at treeline and below. The new storm snow will initially have a poor bond to these buried interfaces and lower elevation snow will likely become moist on Sunday. Strong easterly winds have redistributed the new snow onto leeward aspects forming thicker and likely more reactive slabs. Forecast weekend winds from the southwest will likely build new wind slabs on easterly aspects. Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north. These buried layers are currently dormant.

Problems

Wind Slabs

The new snow will likely have a poor bond to the plethora of old snow surfaces, especially where it sits on a melt-freeze crust or surface hoar on high northerly aspects. Changing winds from East to West will build wind slabs on most aspects.

Avoid large, unsupported terrain and slopes.Use ridges or ribs to avoid pockets of wind loaded snow.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Loose Wet

Loose wet avalanches may occur at treeline and below due to rising freezing levels.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Use extra caution on solar and or low elevation slopes or if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 25th, 2018 2:00PM