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Avalanche Forecast

Archived

Apr 8th, 2023–Apr 9th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Below Threshold.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Below Threshold.

Regions

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Avalanche danger conditions will deteriorate through the day as snowfall accumulates. Conservative decision making is key. Minimize exposure to avalanche terrain, especially during heavy snowfall and wind. If you see greater than 30 cm of new snow, treat avalanche danger as HIGH.

Confidence

Moderate

Avalanche Summary

Warmer temperatures and some sun effect on Thursday produced wet loose avalanches. Wind slabs were last reported earlier in the week, in north-facing terrain features.

In the White Pass area on Saturday, a rider triggered a cornice fall from a distance, which produced a size 3 persistent slab avalanche on a northeast aspect at 1750 m. The avalanche was 200 cm deep and was suspected of having failed on a layer of facets above a crust buried in January.

Observations are also limited at this point in the season, please post any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

By 4 pm on Sunday, 20-40 cm of new snow may have fallen over another 20 cm of settling snow. Strong southerly winds will redistribute this storm snow into deeper deposits over previously wind-affected snow on north and east-facing slopes. South-facing terrain remains stripped back to a crust by these winds

A weak layer of surface hoar/crust/facets buried in early January is now buried over 1 m deep in most areas. This layer has produced recent avalanche activity in the White Pass region and remains a concern in terrain where the snowpack is thin. The lower snowpack consists of basal facets, particularly in shallow areas.

Weather Summary

Saturday Night

Mostly cloudy with 10-20 cm of snow with strong southerly winds. Freezing levels drop to valley bottom.

Sunday

Cloudy with another 15-30 cm possible and strong southerly winds. Freezing levels around 1000 m.

Monday

A mix of sun and cloud with moderate southwest winds. Freezing levels remain low around 500 m. Flurries are possible in isolated areas.

Tuesday

Mostly sunny with light southwest winds. Freezing levels around 500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Be careful to keep storm day fever from luring you out into bigger terrain features.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.