Avalanche Forecast

Issued: Apr 11th, 2018 4:02PM

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

ghelgeson, Avalanche Canada

South Columbia.

It is a good time to be traveling in the mountains, but be careful with fresh shallow wind slabs on all aspects near ridge crest, be mindful of the threat posed by large cornices and watch for small loose avalanches in the afternoon.

Summary

Confidence

High -

Weather Forecast

A gulf Alaska "mother low" continues to sling smaller lows at the province keeping temperatures cool and offering small amounts of precipitation to the Columbias. There is potential for a stronger system to move into the region this weekend, stay tuned for more details. THURSDAY: Broken cloud cover, freezing level beginning around 1000 m rising to about 1600 m, light northerly wind, 3 to 8 mm of precipitation possible.FRIDAY: Clear skies in the morning building to broken cloud cover in the afternoon, freezing level beginning around 1000 m rising to about 1600 m, light west/southwest wind, trace of precipitation possible.SATURDAY: Broken cloud cover, freezing level holding around 1500 m, moderate to strong southwest wind, 1 to 5 mm of precipitation possible.

Avalanche Summary

Reported avalanche activity on Tuesday was limited to a natural size 2 wind slab avalanche that was observed on a north facing feature at 2800 m.On Monday natural loose wet avalanches to size 2 were reported on all aspects with the exception of north between 1500 and 2500 m. A skier triggered size 1.5 storm slab was reported from a west/northwest facing feature between 1800 and 2200, failing on a crust.Loose wet avalanche activity to size 2.5 was widespread Sunday involving all aspects as high as 2500 m. A natural wet slab avalanche was observed on a south facing slope at 2600 m as well.

Snowpack Summary

A thin surface crust is now present on all aspects to at least 2300 m. This crust likely goes even higher on south facing aspects, and there may be a bit of preserved cold snow on high elevation north facing features. There are now a few different crusts in the upper 50 cm of the snowpack, but they have not been problematic. Fresh wind slabs have started to form immediately lee of ridge crest, continued new snow and wind should fuel their development through the weekend.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 60 to 110 cm below the surface. This buried crust/surface hoar interface was widely reactive last week, but has not produced any avalanche activity in the last few days. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it fail. Deeper persistent weak layers from December and January are dormant at this time.

Problems

Wind Slabs

Southerly winds have formed shallow wind slabs immediately lee of ridge crest on north facing terrain. New snow and northerly winds Thursday are expected to form wind slabs on south aspects too.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use ridges or ribs to avoid pockets of wind loaded snow.Sluffs may be easy to trigger in steep terrain that is sheltered from the wind

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

Warming temperatures and a bit of sun may destabilize the snow surface and initiate loose wet avalanche activity which will likely be most pronounced on steep south facing features. The likelihood of cornice failure also increases in the afternoon.

Large cornices become weak with daytime heating, avoid traveling on or underneath them.Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Use caution above cliffs and terrain traps where loose avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 12th, 2018 2:00PM