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Avalanche Forecast

Archived

Apr 12th, 2018–Apr 13th, 2018

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

South Columbia.

Wind slabs can be found in leeward areas near ridge crests, while moist or wet snow is a concern on sunny and lower elevation slopes. Also be wary of large cornices that can become weak with warming.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

TONIGHT: Flurries, clearing. Accumulation 2-5 cm. Ridge wind light to moderate, northwest. Alpine temperature near -6. Freezing level 500 m.FRIDAY: Increasing cloud and flurries. Accumulation trace. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1700 m. Flurries or snow overnight.SATURDAY: Mostly cloudy, flurries. Accumulation 5-15 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1600 m.SUNDAY: Mostly cloudy, flurries ending. Accumulation 2-4 cm. Ridge wind light to moderate, southeast. Alpine temperature near -4. Freezing level 1600 m.

Avalanche Summary

Thursday there were reports from Glacier National Park of a loose wet size 2 on a south aspect at 2100 m,  and a size 4 wind slab that occurred overnight and is thought to have been cornice triggered on a north aspect at 2800 m.On Wednesday there were reports of wind slab activity on northerly aspects limited to the recent storm snow as well as loose wet activity on south-facing slopes.Tuesday there was a report of a natural size 2 wind slab avalanche that was observed on a north facing feature at 2800 m.On Monday natural loose wet avalanches to size 2 were reported on all aspects with the exception of north between 1500 and 2500 m. A skier triggered size 1.5 storm slab was reported from a west/northwest facing feature between 1800 and 2200, failing on a crust. And riders near Blue Lake also triggered a size 2 slab avalanche on buried surface hoar on a north aspect at 2000 m. Read MIN report here.

Snowpack Summary

A thin surface crust is now present on all aspects to at least 2300 m. This crust likely goes even higher on south facing aspects, while 5-15 cm of cold snow can be found on high elevation north facing aspects. There are now a few different crusts in the upper 50 cm of the snowpack, with only the most recently crust posing a concern in wind-loaded areas. There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 60 to 110 cm below the surface. This buried crust/surface hoar interface was widely reactive last week, but has not produced any avalanche activity in the last few days. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think larger triggers such as; sleds, step-down from a surface avalanche or, a cornice collapse).Deeper persistent weak layers from December and January are dormant at this time.

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.

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.