Avalanche Forecast

Kootenay Boundary

Date issued

Mar 16, 2018 - 4:49 PM

Valid until

Mar 17, 2018 - 2:00 PM

Prepared by

cgarritty

Low danger doesn't mean you get to turn off your brain. Normal cautions will help you to manage lingering wind slabs, looming cornices, and the daily cycle of loose wet avalanche conditions.

Regular season
Friday - March 16, 2018
Alpine

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.

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.

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.

Saturday - March 17, 2018
Alpine

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.

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.

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.

Sunday - March 18, 2018
Alpine

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.

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.

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: Wind Slabs

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

Isolated wind slabs on high north aspects may overlie weak layers of surface hoar. Loose wet avalanche conditions increase with daytime warming at lower elevations and on south aspects.

Travel and Terrain Advice
  • Use extra caution on solar slopes, or if the snow is moist or wet.
  • Extra caution needed around cornices with current conditions.
  • Be careful around wind loaded pockets near ridge crests and roll-overs.

Avalanche Summary

Several more loose wet avalanches were reported on Tuesday. Explosives control in the Kootenay Pass area produced eight results from size 2-2.5. Another natural size 2 was noted for releasing two hours after the sun had left the slope.

Avalanche activity through the end of last weekend into Monday focused on a natural solar induced loose wet avalanche cycle on south and west aspects in the alpine an treeline to size 2. On Friday reports indicate numerous size 2-2.5 natural and explosive controlled storm snow avalanches running on all aspects in the alpine and at tree line. There were also several skier triggered storm slab avalanche size 1.5-2 both Friday and Saturday on north aspects in the alpine and tree line.

Snowpack Summary

A mix of light rain and wet flurries brought about 7 cm of new snow to the region on Wednesday. Where it arrived as snow, this precipitation buried a moist crust on solar aspects and a new layer of surface hoar on sheltered north aspects.

Last week's snow was redistributed by predominantly west and southwest wind, forming wind slabs at high elevations. On north aspects these older slabs may be sitting on a layer of surface hoar about 25-40 cm below the surface.

A mix of weak layers exists 50-100 cm below the surface, including small surface hoar on shady aspects and a crust on solar aspects. These layers are expected to have gained strength from recent cycles of warming and cooling. Like other deeper weak layers that formed in January and December, they are considered dormant at this time. These deeper layers include several surface hoar and facet layers 1 to 2 m below the surface and a crust/ facet interface near the base of the snowpack.

Weather Forecast

Saturday: Sunny. Light northeast winds. Freezing level to 1800 metres with alpine high temperatures around 0.

Sunday: Cloudy with isolated flurries bringing a trace to 4 cm of new snow. Light southwest winds. Freezing level to 1400 metres with alpine high temperatures around -2.

Monday: Cloudy with continuing light flurries bringing 2-4 cm of new snow. Light southwest winds. Freezing level to 1400 metres with alpine high temperatures around -3.

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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