Avalanche Forecast
North Columbia
A variety of weak layers continue to produce large human triggered avalanches. We're still managing a mid-winter snowpack at and above treeline that requires thoughtful terrain selection.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use caution around sheltered steep or convex slopes where buried surface hoar may be preserved.
- Minimize exposure to steep planar south-facing slopes - especially if they see sunshine.
- Choose well supported terrain without convexities.
Avalanche Problem 2: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Strong and shifting winds have blown loose snow into wind slabs on a wide range of aspects in wind-affected areas. The most recent strong winds came from the north, so be especially cautious around recently loaded south aspects.
Travel and Terrain Advice
- Be especially careful with wind loaded pockets near ridge crests and roll-overs.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Avalanche Summary
On Wednesday a cornice fell and subsequently triggered a size 2.5 wind slab on a northeast facing slope at 2500 m with a crown 100 cm in depth, suggesting it failed on the mid-March Persistent Weak Layer (PWL). A skier accidentally triggered a small storm slab avalanche on an unsupported pillow feature that faced northeast at 1900 m.
On Tuesday a skier remote triggered a size 2 avalanche on an east facing slope at 1700 m. The avalanche had a crown depth of 50 m running on the March 29th crust. A natural size 2 wind slab from a northwest facing slope at 2500 m was also reported.
On Monday a size 3 persistent slab avalanche was remotely triggered by explosive control work. Numerous small (size 1-1.5) and reportedly hard wind slabs were also triggered on various aspects with both explosives and ski cutting. One large (size 2.5) natural cornice fall was reported as well.
Over the weekend large storm slabs failed naturally and were triggered by both skiers and control work. Sizes ranged from 2-3, with crown depths varying from 30-100 cm. This activity occurred on all aspects but was focused at alpine elevations.
Snowpack Summary
Tuesday night's storm produced 10 cm of cold snow with very little wind.
A variable 5 to 20 cm of snow Sunday night put storm totals from the past week at 40 to 90 cm, with amounts that taper with elevation. The snowfall was initially accompanied by strong south winds followed by strong north winds, so a mix of old/stubborn as well as newer more reactive wind slabs can be found on a range of aspects at higher elevations.
Below the wind-affected surface, a few regionally variable weak layers exist within the upper 40 to 90 cm of snow. Breaks in the storm allowed for the formation of sun crusts on sun exposed slopes as well as surface hoar on shaded aspects.
The mid-March PWL consists of crust/surface hoar and is now buried up to a metre deep. This PWL continues to produce large avalanches daily. The potential for deep 'step down' avalanches can't be dismissed.
Deeper persistent weak layers from January and December are still being monitored by professionals, but are generally considered dormant.
Weather Forecast
The current weather pattern looks more like February than April, but we will take it! Freezing levels are expected to rise just a bit over the next few days and light daily snowfall should continue through the weekend
THURSDAY NIGHT: Freezing level near valley bottom, light southwest wind, 2 to 5 cm of snow possible.
FRIDAY: Overcast, freezing level beginning near valley bottom rising to about 1000 m, light southerly wind, trace of snow possible.
SATURDAY: Overcast, freezing level beginning near valley bottom rising to around 1000 m, light to moderate southerly wind, 3 to 6 cm of snow possible.
SUNDAY: Overcast, freezing level beginning around 500 m rising to about 1500 m, light to moderate west/southwest wind, 1 to 3 cm of snow possible.
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Weak layers of crust and surface hoar from last month are now buried up to 90 cm deep and have shown prolonged reactivity since the last storm. Manage the uncertainty around triggering these layers by sticking to lower angle, supported slopes.