Avalanche Forecast

Archived

Mar 21st, 2022–Mar 22nd, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

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 Inland.

Avalanche danger will increase as new snow and wind form fresh wind slabs at upper elevations. Don't forget about a buried weak layer that remains triggerable around treeline.

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Monday night: Snowfall 5-10 cm. Strong southwest wind. Alpine temperature around -2 °C. Freezing level rising to 1500 m.

Tuesday: Snowfall 5-10 cm. Strong southwest wind. Alpine high around -1 °C. Freezing level 1700 m.

Wednesday: Overnight snowfall 5-10 cm then clearing. Moderate southwest wind. Alpine high around -6 °C. Freezing level 1000 m.

Thursday: A mix of sun and cloud. Moderate south wind. Alpine high around -5 °C. Freezing level 1200 m.

Avalanche Summary

On Sunday, natural cornice-triggered wind slab avalanches were reported up to size 2.

Persistent slab avalanches on a weak layer of surface hoar crystals buried in late February have surprised a few people in the last week with quickly propagating accidental and remote triggers. The layer has been most active on north-northeast aspects between 1200 and 1600 m in areas north of Hazelton.

Snowpack Summary

Strong winds have blown new and recent snow into wind slabs at upper elevations.

A few sun crust and surface hoar layers exist in the upper snowpack. The most concerning of which is a layer of surface hoar crystals found 30-45 cm deep. It has a tendency to surprise riders given it's spotty distribution, most often found on north to east aspects around treeline.

A thick crust formed in mid-February is now buried 50-80 cm deep. It is unlikely to present an avalanche problem under the current conditions and in fact bridges any underlying instabilities in the lower snowpack.

Terrain and Travel

Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
Dial back your terrain choices if you are seeing more than 20 cm of new snow.
Be aware of the potential for large avalanches due to the presence of buried weak layers.
Surface hoar distribution is highly variable. Avoid generalizing your observations.
Caution around convexities or sharp changes in terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.