Avalanche Forecast

Issued: Apr 9th, 2019 4:12PM

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

swerner, Avalanche Canada

Northwest Coastal.

Wind slabs will likely be more reactive on North facing, high alpine slopes. Especially where they sit above a buried crust. Loose wet avalanches are more likely to occur when the sun comes out.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

As the current low pressure system tracks South the region will see a fairly unsettled weather pattern through the forecast period. TUESDAY NIGHT: Light snow amounts 5-15 cm at upper elevations and freezing levels 700 m. Ridgetop winds light with strong consistent gusts from the southwest.WEDNESDAY: Cloudy with some sunny periods and light snow 3-5 cm. Alpine temperatures near -1 and freezing levels 1000 m. Ridgetop winds 10-30 km/h from the southwest.THURSDAY: A mix of sun and cloud. Alpine temperatures near 0 degrees and freezing levels 1400 m. Ridgetop winds light from the southwest.FRIDAY: Cloudy with some sunny periods. Alpine temperatures near 0 to 3 degrees and freezing levels 1400 m. Ridgetop winds light with strong SW gusts.

Avalanche Summary

Reports on Tuesday indicated no recent avalanche activity. We received a great MIN report from the Shames backcountry that describes an active wet loose avalanche cycle to size 1.5, more details here. A combination of new snow and wind may increase the reactivity of the existing wind slabs. The sun can really pack a punch this time of year and trigger loose wet avalanches.

Snowpack Summary

New storm snow expected overnight on Tuesday will add to the 10 to 40 cm of storm snow from last weekend that now rests on a weak layer buried April 4th which consists of crust, surface hoar and facets. The crust is widespread and up to 4 cm thick. Spotty surface hoar and facets have been reported on top of the crust on high elevation north facing slopes. Moderate to strong wind generally out of the south over the weekend likely formed fresh slabs which may remain sensitive to human triggering. North facing alpine terrain also has a layer of facets down 40 to 100 cm below the surface, but this layer has not been recently active and is likely trending towards dormancy.Below treeline the snowpack is isothermal throughout much of the forecast region.

Problems

Wind Slabs

10 to 40 cm of storm snow rests on a widespread crust. Strong southerly winds have likely formed fresh slabs in high elevation north facing features. Human triggering is most likely immediately lee of ridgecrest.

Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Periods of sunshine may initiate a loose wet avalanche cycle in the new snow. The likelihood of loose avalanches increases as temperatures warm through the day and/or if the sun comes out for a prolonged period of time.

Loose avalanches may start small but they can grow and push you into dangerous terrain traps.A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Apr 10th, 2019 2:00PM