Avalanche Forecast

Issued: Mar 18th, 2019 5:04PM

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

swerner, Avalanche Canada

South Coast.

Persistent warm temperatures are penetrating and destabilizing the upper snowpack. Natural avalanche activity is likely. Pay attention to sunny slopes and avoid travel under avalanche paths especially slopes with cornices overhead.

Summary

Confidence

Moderate -

Weather Forecast

Hot and sunny with freezing levels through the roof! Very little temperature driven overnight re-freeze is expected. TUESDAY: Mostly clear skies and freezing levels holding strong above 3100 m. Alpine temperatures near + 16.0 degrees with moderate southeast wind at ridgetop. Alpine temperatures may drop to + 4.0 degrees overnight.WEDNESDAY: Mix of sun and cloud with freezing levels above 3100 m. Alpine temperatures +15.0 degrees with light southeast ridgetop winds. THURSDAY: Cloudy periods.Â Alpine temperatures near + 10.0 degrees and freezing levels 2400 m during the day.

Avalanche Summary

On Sunday, a widespread natural wet loose avalanche cycle occurred and was reported up to size 1.0. As the heat continues to penetrate the snowpack we suspect widespread natural wet avalanches will continue through the forecast period. These will be large and small avalanches on all aspects and elevations.

Snowpack Summary

The heat wave has likely eliminated any trace of cold snow, but you may still find some on high elevation north features. Wind slabs are likely done at this point, zapped of their strength by time and warming. We're very concerned about the upper 20 to 30 cm of snow that sits on crust on steep south slopes and possibly weak surface hoar crystals on sheltered and shaded slopes.The even bigger questions are deeper in the snowpack. A layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. This layer is most prominent in the North Shore Mountains on north aspects. With little overnight re-freeze the warm temperatures will penetrate deeper allowing melt and a lot of water which will lubricate the upper snowpack. It also allows the upper snowpack to start creeping downhill at an accelerated rate. Its hard to say how many hot days and warm nights it will it take to wake up the more deeply buried weak layers. We're not sure, but now is probably a time to let the mountains do their thing from afar and check back in when the freezing levels return to seasonal norms which could happen by next weekend.

Problems

Persistent Slabs

A warm night followed by another day of clear skies and hot temperatures is expected to further destabilize the upper 20 to 30 cm of snow which will likely begin failing naturally. Even deeper avalanches are well within the realm of possibility.

The likelihood of deep persistent slab avalanches will increase with each day of warm weather.Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 2.5

Loose Wet

Loose wet activity is expected to continue on all aspects and elevations. Cornices are going to begin to loosen up and drop on the slopes below. You don't want to be under or near one of these monsters when they fail.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Cornices become weak with daytime heating or solar exposure.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Valid until: Mar 19th, 2019 2:00PM