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Avalanche Canada jsmith, Avalanche Canada

North Columbia Avalanche Forecast

Apr 22nd, 2019 4:59PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Loose Wet.

New snow and moderate winds Monday night may create small wind slabs that when in motion, step-down to the recent storm snow, resulting in large avalanches.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Cloudy with alpine flurries; 5-10 mm. / Moderate, southwesterly winds / Alpine low -1 C / Freezing level 1900 m.

TUESDAY: Cloudy with isolated alpine flurries; 2-5 mm / Moderate, southwesterly winds / Alpine high 4 C / Freezing level 2000 m.

WEDNESDAY: Sunny / Moderate, westerly winds / Alpine high 3 C / Freezing level 1800 m.

THURSDAY: Mostly sunny / Light, westerly winds / Alpine high 4 C / Freezing level 2000 m.

Avalanche Summary

No new avalanches were reported in this region on Sunday. However, there are currently very few professional observers submitting daily observations. Please submit your observations to the MIN. Photos of avalanches or current conditions are particularly useful.

On Saturday, numerous, natural loose wet avalanches up to size 1.5 were reported on steep solar aspects at treeline and above in the afternoon.

A widespread storm slab avalanche cycle to size 3.5 on all aspects in the alpine was reported on Friday. Although not in this region, check out these two MIN reports from Saturday in Glacier National Park HERE. and HERE.

Snowpack Summary

30-40 mm of rain has soaked the snowpack at treeline and below. The rain/snow boundary on Friday was around 2100 m. New snow amounts in the alpine will taper rapidly with elevation and likely equate to around 15-25 cm of moist snow at upper elevations adding to the 20-40 cm recent snow which overlies a crust everywhere except high elevation, north facing terrain where preserved surface hoar (weak, feathery crystals) may be present in isolated locations down 30-60 cm. A similar layer buried in early April is down 50-80 cm. Smaller storm slab avalanches may step down to one of these deeper weak layers.

Below treeline, snow is disappearing rapidly.

Problems

Wind Slabs

New snow and moderate winds Monday night may create small wind slabs that when in motion, ‘step-down’ to the recent storm snow, resulting in large avalanches.

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Pay attention to changing conditions with elevation/aspect.
  • Use small slopes without consequence to test the bond of the recent snow.

Aspects:

North, North East, East, South East, North West.

Elevations:

Alpine.

Likelihood

Likely - Possible

Expected Size

1 - 2

Loose Wet

If temperatures remain warm, loose wet avalanches are still possible on cloudy days due to the green-house effect.

  • Avoid terrain traps such as cliffs and gullies that increase the consequence of small avalanches.
  • A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.

Aspects:

All aspects.

Elevations:

Treeline.

Likelihood

Possible - Unlikely

Expected Size

1 - 1.5

Valid until: Apr 23rd, 2019 2:00PM