Avalanche Forecast

North Columbia

Date issued

Mar 26, 2018 - 4:07 PM

Valid until

Mar 27, 2018 - 2:00 PM

Prepared by

mgrist

Strong winds and new snow will be driving the avalanche danger to HIGH. If you see more than 30cm of new snow, avoid all avalanche terrain, free from overhead hazard.

Regular season
Monday - March 26, 2018
Alpine

4 - High

Very dangerous avalanche conditions.Travel in avalanche terrain not recommended.

Natural avalanches likely;human-triggered avalanches very likely.

Large avalanches in many areas;or very large avalanches in specific areas.

Treeline

4 - High

Very dangerous avalanche conditions.Travel in avalanche terrain not recommended.

Natural avalanches likely;human-triggered avalanches very likely.

Large avalanches in many areas;or very large avalanches in specific areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Tuesday - March 27, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Wednesday - March 28, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Avalanche Problem 1: Storm Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Strong winds and new snow will make for very touchy avalanche conditions. High north aspects are a particular concern due to extra loading on buried surface hoar that could lead to easier triggering and deeper releases.

Travel and Terrain Advice
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Use conservative route selection, choose moderate angled and supported terrain with no consequence.

Avalanche Summary

On Monday, backcountry skiers triggered a size 2 wind slab on a northeast aspect near 2050m. The slab's thickness varied from 40-60cm.

On Saturday we received reports of several wind slabs and storm slabs to size 2.5, mostly on northerly aspects above 2200m. Also on Saturday, a wet loose size 1.5 avalanche injured a skier in Glacier National Park on a west aspect near 2000m.

Snowpack Summary

New snow fall amounts into Monday range from 5-11 cm. Winds have been moderate south/east, creating fresh wind slabs on down wind (lee) slopes.

Wind slabs from late last week (thanks to south / east winds) remained reactive throughout the weekend on immediate lee features.

Isolated pockets of surface hoar (buried March 18th) have been reported between old storm snow layers on shaded aspects at higher elevations and may be found approximately 25-40 cm below the surface.

New snow amounts taper with elevation and below 1800 m, reduced accumulations have buried a supportive crust on all aspects.

Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, large cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.

Weather Forecast

Snow and strong winds on Tuesday; clearing up Wednesday into Thursday.

TUESDAY: Snow (20-30cm). Moderate to strong south / west winds 30-70 Km/hr. Freezing level rising to 1600 metres with alpine high temperatures around -5.

WEDNESDAY: Sunny with cloudy breaks and isolated convective flurries. Moderate northwest winds 20-45 Km/hr. Freezing level to 1400 metres with alpine high temperatures around -7.

THURSDAY: Cloudy with flurries bringing up to 5-10 cm of new snow, increasing overnight. Moderate southwest winds 20-40 Km/hr. Freezing level 1400 metres with alpine high temperatures of -5.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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