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Avalanche Forecast

Archived

Feb 5th, 2022–Feb 6th, 2022

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

Regions

North Rockies.

Rising temperatures will keep the likelihood for humans to trigger avalanches increased, particularly where recent snow loaded a buried weak layer. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

SATURDAY NIGHT: Mostly cloudy, up to 5 cm new snow, strong southwest wind, alpine temperature -3 C, freezing level 1400 m. 

SUNDAY: Mix of sun and cloud with intermittent snowfall, up to 5 cm new snow, moderate to strong southwest wind, alpine temperature 0 C, freezing level 1800 m.

MONDAY: Cloudy with snowfall, accumulation 20 to 30 cm, strong southwest wind, alpine temperature -1 C, freezing level 1500 m.

TUESDAY: Cloudy, 5 to 10 cm new snow, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1500 m.

Avalanche Summary

On Friday a natural avalanche cycle was reported with small storm slab avalanches up to size 1.5. Most avalanches were observed at and below treeline. A couple large (size 2) slab avalanches were reported at treeline on a southwest and an east aspect. Observations on Friday were limited due to visibility.

Large avalanches are expected in areas where the buried surface hoar described in the Snowpack Summary exists. 

Looking towards Sunday, avoidance of consequential avalanche terrain is your best bet for having a safe day. Storm and wind slabs will be very touchy due to all the recent snow and wind. The snow will need time to stabilize.

Snowpack Summary

The recent storm brought 40 to 60 cm for much of the region, with the most in the southwest of the region and the least to the east of the divide and in the north. The snow has likely formed storm slabs in sheltered areas and wind slabs in lee terrain features from strong southwest wind. These slabs will remain touchy for the remainder of the weekend as the freezing level rises and the air gets warmer.

The snow will be particularly touchy where it sits on a weak layer of surface hoar crystals. Reports suggest that the surface hoar is likely most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.