Avalanche forecast

North Columbia

Mar 20 – 21, 2021Avalanche Canada
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Avalanche danger

Mon
Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Expect to find an increasingly reactive slab as snowfall accumulates and anywhere fresh snow is influenced by the wind. Be mindful that the best riding conditions may overlap with the deepest deposits and touchiest slabs.

Avalanche problems

  • Wind Slabs

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

    As southwesterly winds redistribute loose snow, the best riding conditions will overlap with the highest avalanche hazard. High elevation north, northeast and east facing slopes may have a thin layer of surface hoar in place and continued southwest winds are expected to build fresh slabs above this surface hoar. Carefully assess your line for touchy wind slabs before committing. This problem is expected to increase in sensitivity as new snow and wind continue to build the slab. Steep, convex slopes below alpine ridge tops are the most likely places to trigger these slabs.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Where cornices exist they pose a threat both from the potential for them to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. They are most likely to fail during periods of solar radiation or loading from snow/wind.

Confidence

Low - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

SATURDAY NIGHT: Flurries, up to 5 cm. Light to moderate southwest wind, alpine temperature low -8C, and freezing level dropping to valley bottom.

Weather models are showing a band of moisture moving from the Shuswap to the Purcells through the Nakusp area to the TCH corridor late Saturday evening and overnight, and may produce enhanced precipitation in localized areas of up to 25cm.

SUNDAY: Flurries and snow, 10-20 cm accumulating by the end of the day. Moderate southwest wind, alpine high -3C, and freezing level beginning near valley bottom rising to about 1400 m.

MONDAY: Flurries continuing into Monday, 5-10 cm of snow possible. Light northwest wind, alpine high -6C, and freezing level beginning near valley bottom rising to about 1300 m.

TUESDAY: Mostly cloudy. Light to moderate southwest wind, alpine high -1C, and freezing level beginning near valley bottom rising to about 1400 m.

Avalanche Summary

On Friday, several glide slab avalanches (size 2-3) were observed on south and east aspects around the TCH highway corridor. Loose wet avalanches to size 2.5 were reported around the region; a natural loose-wet cycle was reported around Rogers Pass initiating with evening rainfall.

Avalanche activity on Thursday was limited to two glide slabs to size 2.5 releasing around 1750 m on steep south facing slopes.

On Tuesday, a size 3.5 deep slab avalanche was reported from the Northern Monashees. It was triggered by cornice fall on an east-southeast aspect above 2200 m. Additionally, a natural glide slab size 2.5 was reported from a West aspect at 1500 m and numerous loose wet to size 2 in steep southerly terrain. 

On Monday, numerous natural loose wet avalanches were reported from southerly aspects above 1900 m.

Snowpack Summary

15-30 cm snow accumulated around the region through Saturday. Flurries and wind formed fresh slabs in immediate lees. New snow covers dry settled snow and surface hoar (up to 10 cm) on northerly aspects above 2000m, and crusts on solar aspects and lower elevations. Large cornices loom over alpine ridgetops.

Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have recently been unreactive and no recent avalanches have been reported on these layers. 

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Wind slabs are most reactive during their formation.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Dial back your terrain choices if you are seeing more than 25cm of new snow.

Regions covered