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Avalanche Forecast

Archived

Apr 2nd, 2017–Apr 3rd, 2017

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

Regions

Northwest Inland.

Watch for changing snow conditions when the sun comes out. Slab avalanche activity is possible at higher elevations, and will be more likely when the snow is soft and warm.

Confidence

Moderate - Due to the number and quality of field observations

Weather Forecast

MONDAY: Sunny skies, light winds, and freezing level rising to 1200 m after an overnight freeze.TUESDAY: Overcast with light snow in the evening, increasing south wind, and freezing level climbing to 1400 m. WEDNESDAY: Scattered flurries with about 5 cm, strong south wind, and freezing level around 1400 m.

Avalanche Summary

A natural cornice fall released a wind slab or perhaps a persistent slab on a northeast aspect that was size 2.5; this was reported from the Microwave on Thursday but may have occurred on Wednesday (see the full MIN report here). Storm slabs up to size 2.5 were reported from the western extent of the region in the Howson's, where the snowpack is more like the Northwest Coastal region. No new avalanches have been reported from the rest of the region.

Snowpack Summary

Light snow combined with moderate southwest winds has developed wind slabs in the alpine and in some exposed treeline locations. Periods of sun and high daytime freezing levels have developed crusts below treeline and on sun exposed terrain at all elevations. The snow may be moist or wet below treeline during the warmest part of the day. The February crust and facet layer was reported to be down 75-90 cm in the Houston Telkwas sled area on Wednesday. The deep persistent weak layer of facets and/or a crust that were buried early in the winter are still lingering near the bottom of the snowpack. This MIN report found the deep weak layer strengthening in the Telkwas.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.