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Avalanche Forecast

Archived

Mar 22nd, 2022–Mar 23rd, 2022

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

Regions

North Rockies.

A cooling trend is expected over the day, but the snowpack may remain unstable until it hardens. Assess for instability before pushing into big terrain.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

TUESDAY NIGHT: Cloudy with rain switching to snow, trace accumulation in the south of region and 10 to 20 cm above the rain-snow line in the north of the region, 60 to 80 km/h southwest wind, alpine temperature 0 C, freezing level 2300 m.

WEDNESDAY: Cloudy with snowfall, trace accumulation in the north of the region and 5 to 10 cm in the south of the region, 40 km/h west wind, alpine temperature -5 C, freezing level dropping to 1300 m.

THURSDAY: Clear skies with no precipitation, 10 km/h west wind, alpine temperature -7 C.

FRIDAY: Mostly cloudy with no precipitation, 10 km/h south wind, alpine temperature -6 C.

Avalanche Summary

Minor avalanche activity was noted on Monday. A small wind slab was observed out of very steep terrain on a northwest aspect and small loose activity occurred below 1300 m. 

Although not yet reported, we expect to receive reports of loose wet activity from the freezing level rise. Similar activity is anticipated Tuesday night into Wednesday morning and perhaps continue at lower elevations until the freezing level drops. Assess for wind slab formation at higher elevations.

Snowpack Summary

Freezing levels reached the lower alpine, warming up the snowpack. With a freezing level drop over Wednesday, rain will switch to snow and the snowpack will begin to stabilize. Above the freezing level, wind slabs may be found due to new snow and strong southwest wind.

A weak layer may be found around 40 to 80 cm deep in the western half of the region. The layer consists of surface hoar crystals in treeline terrain in areas sheltered from the wind and otherwise a hard melt-freeze crust associated with weak faceted grains on sun-exposed slopes. Check out this blog for more information. This layer hasn't shown reactivity since last week but may still linger in portions of the region.

The remainder of the snowpack is well-bonded.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.