Avalanche Forecast

Archived

Apr 18th, 2024–Apr 19th, 2024

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Coastal, Boundary, Stewart.

Spring is a tricky time. Heat-related cornice and wet loose problems rise and fall each day, but deeper snowpack weaknesses remain in play. Use conservative terrain to manage uncertainty.

Confidence

Moderate

Avalanche Summary

A large (size 2) loose wet avalanche triggered a slab about 50 cm deep on Tuesday at 1700 m. It is possible that it triggered the weak layer described in the snowpack summary.

Otherwise, the most recent persistent slab activity was a week ago. Although likelihood is decreasing, it remains possible for humans to trigger this buried weak layer.

Also expect sun-exposed slopes to become unstable with daytime warming, possibly triggering wet avalanches or releasing cornices.

Snowpack Summary

Dry, settled snow is found on shaded aspects in the alpine. A hard melt-freeze crust exists on the snow surface on sun-exposed slopes to the mountain tops and on all aspects below treeline. The crust will transition to wet snow with daytime warming and re-freeze at night.

50 to 100 cm of snow overlies a hard melt-freeze crust from early April. The overlying snow is slow to bond to the crust where pockets of weak surface hoar or faceted grains rest on the crust, which is most likely on northerly aspects at treeline and alpine elevations.

Weather Summary

Thursday night

Clear skies. 20 km/h east ridgetop wind. Treeline temperature around +1 °C. Freezing level rising to 1800 m.

Friday

Clear skies. 20 to 30 km/h east ridgetop wind, increasing. Treeline temperature 0 °C. Freezing level to 1500 m.

Saturday

Clear skies with cloud invading late afternoon. 20 to 30 km/h southeast ridgetop wind. Treeline temperature 0 °C. Freezing level to 1500 m.

Sunday

Increasing cloud with isolated flurries in the afternoon. 10 - 15 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level to 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.