Avalanche Forecast

Issued: Apr 15th, 2019 5:20PM

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

Avalanche Canada ghelgeson, Avalanche Canada

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Winter is going out with a bang after producing 10 to 20 cm of storm snow Saturday night. Rising temperatures and the strong April sun could produce a turbo charged loose wet avalanche cycle on Tuesday.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

A rather slack and warm pattern is setting up with the big story being the steadily rising freezing level. It doesn't look like we'll get any significant precipitation this week. MONDAY NIGHT: Freezing level around 500 m, light variable wind, no new snow expected. TUESDAY: Broken cloud cover clearing to just a few clouds in the late afternoon, freezing level rising to around 2100 m, light variable wind, no significant snowfall expected. WEDNESDAY: Broken cloud cover, freezing level rising to around 2200 m, moderate to strong west wind, no significant snowfall expected. THURSDAY: Scattered cloud cover, freezing level rising to around 2800 m, moderate to strong west/southwest wind, no significant precipitation expected.

Avalanche Summary

No new avalanche activity reported from this region, the following is from the Lizard Range:On Sunday storm slabs were quite sensitive to human triggering to size 2 on north through east facing slopes in the alpine and down into treeline. A little further down into treeline the snowpack was well bonded to the old crust, check out this MIN report for more details.A natural avalanche cycle occurred Saturday night, the highlights were storm slabs up to size 2 on northeast facing alpine terrain around 1700 m. A natural cornice failure was observed from a north facing ridgeline which subsequently triggered a size 2.5 storm slab involving the new snow. Control work produced storm slabs to size 2. We received a great MIN report of a small storm slab from Saturday morning, and this was well before the storm really kicked into gear. 

Snowpack Summary

The Saturday Night storm delivered 10 to 20 cm of snow which makes for 20 to 40 cm of new snow in the last week. This snow sits above a widespread supportive crust. Steep, north facing, alpine terrain may still hold a cold, dry, snowpack where fresh storm slabs are thought to be widespread. Steep north facing terrain is also harboring a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible, especially in rocky alpine terrain with a shallow or highly variable depth snowpack. It looks like it is going to warm up this week and all the new snow will likely produce a widespread and powerful loose wet cycle. During the heat of the day, especially under direct sun, the snow surface will become moist or wet almost everywhere (except for high elevation north) and loose wet avalanches could run far.Below treeline the snowpack has melted or is isothermal.

Problems

Loose Wet

An icon showing Loose Wet
Sunny breaks combined with fresh storm will likely turbo charge loose wet avalanche activity. The likelihood of loose avalanches increases as temperatures warm throughout the day and/or if the sun comes out for an extended period of time.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.Loose avalanches may start small but they can grow large and destructive in these conditions.

Aspects: East, South East, South, South West, West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Storm Slabs

An icon showing Storm Slabs
10 to 20 cm of storm snow rests on a widespread crust. The "crust free" exception may be high elevation north facing alpine terrain. Storm slabs likely remain sensitive to human triggering, especially in wind loaded terrain.
Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.Recent new snow may be hiding windslabs that were easily visible before the snow fell.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 16th, 2019 2:00PM

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