North Columbia Avalanche Forecast

Mar 25th, 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.

Expect Danger to be one-step higher in localized areas in the far north of the region that received 25+ cm. of recent convective snowfall.

Small wind slabs below ridgetops are the primary concern for the rest of the region.

Summary

Confidence

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

Weather Forecast

WEDNESDAY NIGHT:Increasing cloudiness, light northwest winds, alpine low -10 C, freezing level valley bottom.

THURSDAY: Mostly cloudy, moderate west winds, alpine high -3 C, freezing level 1300 m.

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

SATURDAY: Snow; 5-10 cm, Moderate to strong west winds, alpine high 1 C, freezing level 1600 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 most of the region Sunday with light variable wind, but moderate gusts at ridge-top may be forming shallow wind slabs. Localized areas in far north of the region (near Valemount) received 25+ cm. of recent convective snowfall. In these areas, I would look out for storm slabs that may become reactive to human triggers as the snow settles.

The recent snow fell 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 26th, 2020 5:00PM