Avalanche Forecast

Issued: Apr 3rd, 2018 5:00PM

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

Avalanche Canada mgrist, Avalanche Canada

Be alert for the new snow going from loose and dry to forming slabs as temperatures warm. Keep a close eye on how the new snow is bonding to the old surface below, especially on sunny aspects.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

Only small amounts of snow on Thursday-Friday. Temperatures stay cool for this time of year.WEDNESDAY: Mainly cloudy with occasional flurries (up to 5 cm) / Moderate south west wind / Alpine temperature -4 / Freezing level 500m rising to 1400m in the afternoon THURSDAY: (Wet) flurries (5-10 cm) or rain at lower elevations / Light to moderate south-west wind / Alpine temperature -3 / Freezing level 1400mFRIDAY: Isolated flurries (5 cm possible) or rain at lower elevations / Moderate south west wind / Alpine temperature -4 / Freezing level 1300m.

Avalanche Summary

On Tuesday, natural avalanche activity was tapering, but human triggered avalanches to size 1.5 were still reported, failing on melt-freeze crusts on sunny aspects, or buried surface hoar on northerly aspects. On Monday we received reports of widespread natural storm slab avalanches to size 1.5 on all aspects in Kootenay Pass. Crowns averaged 10-25cm thickness. On Friday, cornice control work resulted in triggering a size 2 wind slab below, on an east aspect near 2200m. Slab depth averaged 20cm.

Snowpack Summary

Well that was quite a storm, wasn't it Nelson? The region saw wildly variable amounts of new snow on Monday morning, ranging from 2cm to 48cm near Nelson!!! Since then, only 2-4 cm of new snow has fallen, and temperatures stayed cool. The new snow sits on firm crusts on sunny aspects, and all aspects below 1900m. On higher, shady aspects, the new snow may sit on some old wind slabs from last week, or a mix of large surface hoar and surface facets. Another weak layer buried mid March is down 50 to 120cm and is a crust on solar aspects and surface hoar (to 6mm) on high elevation north. A few other persistent weak layers are buried in the mid and lower snowpack, but they have gone dormant and are unlikely to resurface until we move into a period with consecutive above-freezing nights.

Problems

Storm Slabs

An icon showing Storm Slabs
Extra caution is advised where heavy snowfall sits on a firm melt-freeze crust... a perfect sliding layer for slab avalanches.
Check for how the new snow is bonding to the old surface below.Watch for areas with heavy snow fall accumulations... and be prepared to dial back terrain use.Be alert for dry loose sluffs: Pull over from time to time and let it go by on steeper pitches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Apr 4th, 2018 2:00PM

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