North Columbia Avalanche Forecast

Mar 24th, 2020 4:00PM

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

Small wind slabs below ridgetops are currently the primary concern.

Summary

Confidence

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

Weather Forecast

TUESDAY NIGHT: Mostly cloudy, light west winds, alpine low -11 C, freezing level valley bottom.

WEDNESDAY: Mix of sun and cloud, light west winds, alpine high -5 C, freezing level 900 m.

THURSDAY: Cloudy, moderate west winds, alpine high -3 C, freezing level 1200 m.

FRIDAY: Cloudy with possible flurries; 3-5 cm, moderate southwest winds, alpine high 0 C, freezing level 1500 m.

Avalanche Summary

Over the past week, avalanche activity was reported as natural loose dry or loose wet avalanches size 1-2 running in steep, sun-exposed terrain. One large (size 2) slab avalanche released naturally as a result of strong solar radiation on a south aspect at 2500 m. There were also several large cornice failures on northerly aspects (up to size 2.5).

Snowpack Summary

1 to 5 cm fell across the region Sunday with light variable wind, but moderate gusts at ridge-top may be forming shallow wind slabs.

The new snow is falling on a variety of snow surfaces, consisting of sun crusts, hard wind-affected snow, and soft faceted snow. There have also been reports of surface hoar forming on sheltered, shady slopes. See this MIN for a helpful illustration from nearby Glacier National Park. It will be important to track the depth, cohesiveness, and bond of the new snow to these various old snow surfaces across aspects and elevations where you're travelling.

Cornices are large and looming. Two layers of buried surface hoar may be found buried 20-40 cm deep (March 10) and 60-120 cm deep (February 22). Though there is a low likelihood of triggering an avalanche on these layers, the consequences of doing so would be high. Avalanche activity on the Feb 22 layer was last reported on March 8th.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Make observations and assess conditions continually as you travel.
  • Be alert to conditions that change with aspect and elevation.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 1.5

Recent winds may have formed reactive slabs on lee features below ridgetops.

Aspects:

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

Elevations:

Alpine.

Valid until: Mar 25th, 2020 5:00PM