Avalanche forecast

Northwest Inland

Feb 17 – 18, 2021Avalanche Canada
View on map
Archived · expired 6 years ago

Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
Open full map

Highlights

Forecast moderate to strong northwest wind overnight and during the day will form fresh wind slabs in lee terrain features in the alpine and at treeline where soft snow is available for transport. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    The forecast calls for moderate to strong northwest wind overnight and during the day which will form fresh wind slabs in alpine and treeline lee terrain features where soft snow is available for transport. Wind slabs will be especially susceptible to human triggering where they sit on top of weak faceted crystals.

    Recent shifting winds have created wind slabs on multiple aspects and all elevations. Older wind slabs may still be triggered by humans and propagate wider than expected, especially where they sit on a weak faceted crystal layer.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

TUESDAY NIGHT: Clear with cloudy periods, moderate to strong northwest wind, temperature low -15 C.

WEDNESDAY: Mix of sun and cloud, moderate northwest wind, temperature high -8 C.

THURSDAY: Mostly cloudy, trace of new snow, moderate to strong southerly wind, temperature high -9 C.

FRIDAY: Mostly cloudy, up to 5 cm of new snow, moderate to strong southwest wind, temperature high -6 C.

Avalanche Summary

Wind slabs have been reactive to human triggering in wind loaded and cross loaded features over the weekend. Most ski cut results have been of size 1 to 1.5, but bigger terrain features could propagate wider and produce larger avalanches! On Saturday hard wind slabs were easy to trigger in the Crater Lake area as evidenced by this MIN.

In the Babine area a field team noted numerous size 1-2 wind slabs in the alpine on Saturday from the past 36 hours. They also posted this MIN from the Onion. This is in line with other avalanche observations from the outflow wind cycle like this size 2 near Miller Creek.

In the southwest of the region, two natural cornice triggered avalanches of size 2.5 and size 3 were reported on Friday and Sunday. They probably released during the outflow wind cycle.

Snowpack Summary

Small amounts of new snow have fallen on hard slabs, scoured slopes and sastrugi where outflow effects have been the strongest. In sheltered areas, the cold temperatures promoted surface faceting. The late January interface is down 30-50 cm consisting of isolated surface hoar in sheltered locations, and previous wind affected layers in exposed areas. On solar aspects, a buried sun crust can be found in places as well.

The lower snowpack has two decomposing crust layers. The upper crust is 70-140 cm deep and continues to show occasional hard, sudden results in snow pits. The deeper crust at the bottom of the snowpack is more prevalent in shallow snowpack ranges. These deep persistent layers seem to be dormant under the current conditions, but shallow rocky slopes should still be carefully assessed and approached with caution. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Regions covered