Avalanche Forecast
North Columbia
Prolonged reactivity of storm slabs has earned them a persistent slab label, but the avoidance strategy hasn't changed. Keep it in mind as you navigate around the more obvious wind effect.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Be especially careful with wind loaded pockets near ridge crests and roll-overs.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Our mid-March weak layer of crust and surface hoar has been buried by up to 90 cm of storm snow and has shown prolonged reactivity since the last storm. Manage the uncertainty around triggering this layer by sticking to lower angle, supported slopes.
Travel and Terrain Advice
- Choose well supported terrain without convexities.
- Minimize exposure to steep planar south-facing slopes - especially if they see sunshine.
- Use caution around sheltered steep or convex slopes where buried surface hoar may be preserved.
Avalanche Summary
Reports from Sunday included several more storm slab and wind slab avalanches from size 1-2. These were both skier-triggered and ski cut on north to east aspects at around 2000 metres and above. Shallower slab depths have begun to highlight the mid-storm interface indicated in our snowpack discussion, but at least one larger storm slab failed at the deeper late-March layer, now labeled a 'persistent slab'.
Saturday's reports included numerous observations of storm slabs releasing naturally as well as with remote (from a distance) triggering, skier traffic and explosives control. Sizes ranged from 2-3, with crown fracture depths varying from 30-100 cm. This activity occurred on all aspects but was focused at alpine elevations.
Friday's storm caused another natural avalanche cycle with numerous size 1-2 avalanches in the top 20-30 cm of new snow.
Storm slab avalanches have been reported on a regular basis since Tuesday's storm, with natural avalanches up to size 3 initially reported on all aspects from 1900-2800 m. South and west aspects have been most reactive with slabs running on the recently buried late-March crust.
Snowpack Summary
A variable 5-20 cm of new snow over Sunday night has brought storm snow totals from the past week to a wide-ranging 40-90 cm. The snowfall was initially accompanied by strong west wind and formed reactive slabs at higher elevations. More recent north winds reached extreme, so a mix of stubborn old and newer, more reactive wind slabs can now likely be found on a range of aspects.
Below the wind effect at the surface, a break between storm pulses allowed for the formation of yet another layer of sun crust (south aspects) and surface hoar (shaded aspects) that is now buried by 20-30 cm of new snow. The full depth of recent storm snow sits on a persistent weak layer buried in late-March that consist of crusts below 1900 m and on south aspects, and surface hoar on shaded aspects at higher elevations.
A deeper layer buried mid-March is now 60 to 90 cm below the surface, and is similar to the late-March interface.
Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.
Weather Forecast
Tuesday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1100 metres with alpine high temperatures around -8.
Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1000 metres with alpine high temperatures around -9.
Thursday: Cloudy with flurries bringing about 5 cm of new snow, continuing overnight. Light east winds. Freezing level to 900 metres with alpine high temperatures around -10.
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Strong and shifting winds have been blowing loose snow into wind slabs on a wide range of aspects in wind-affected areas. North winds were the most recent, so be especially cautious around freshly loaded south aspects.