Avalanche Forecast

Archived

Mar 7th, 2024–Mar 8th, 2024

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Coquihalla, Manning, Skagit.

Buried weak layers persist and are capable of triggering significant and destructive avalanches.

Confidence

Moderate

Avalanche Summary

Tuesday's reports included a few skier and machine-triggered size 2 (large) persistent slabs in the Coquihalla corridor. An observation flight also confirmed a widespread natural avalanche cycle took place at the end of last week with avalanches reaching size 3 (very large).

Check out this MIN report from the thick of the action on Saturday in the Coquihalla.

Professionals remain concerned about preserved weak layers and very cautious about entering avalanche terrain

Snowpack Summary

Light new snow amounts and a new melt-freeze crust (on solar aspects) have begun to reshape the surface.

Otherwise, 60-100 cm of recent storm continues to settle above a problematic facet/surface hoar/crust layer buried beneath it. This layer has acted as the failure plane in many recent avalanches in this region and adjacent regions and it continues to produce whumpfs and concerning snowpack test results at treeline.

In some areas a second, thicker crust with weak facets above either replaces or is buried just below the layer described above. It similarly continues to produce concerning snowpack test results and may also have been involved in some of the region's recent avalanche activity.

Weather Summary

Thursday night

Mainly cloudy. 10-20 km/h southwest or west alpine winds. Freezing level to valley bottom.

Friday

Cloudy with 1-5 mm of precipitation. 30-40 km/h southwest alpine winds. Treeline temperature 1 °C with freezing level rising to 2000 m.

Saturday

Mainly cloudy with isolated flurries 1-5 cm. 30-50 km/h southwest alpine winds. Treeline temperature reaching 0 °C with freezing levels around 1700 m.

Sunday

Cloudy with flurries bringing 5-10 cm of new snow. 40-50 km/h south alpine winds. Treeline temperature -2 with freezing level falling to 1300 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
Remote triggering is a concern, watch out for adjacent and overhead slopes.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.

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.