Avalanche Forecast
Purcells
Wind slabs remain a concern near ridge crest, new snow and wind Thursday will likely add fuel to that problem. Be mindful of the threat posed by large cornices and watch for loose avalanches in the afternoon too.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Sluffs may be easy to trigger in steep terrain that is sheltered from the wind
- Use ridges or ribs to avoid pockets of wind loaded snow.
- Be very careful with wind loaded pockets, especially near ridge crests and roll-overs.
Avalanche Problem 2: Loose Wet
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Warming temperatures and a bit of sun may destabilize the snow surface and initiate loose wet avalanche activity which will likely be most pronounced on steep south facing features. The likelihood of cornice failure also increases in the afternoon.
Travel and Terrain Advice
- Use caution above cliffs and terrain traps where loose avalanches may have severe consequences.
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
- Large cornices become weak with daytime heating, avoid traveling on or underneath them.
Avalanche Summary
On Tuesday a skier intentionally triggered a size 1 wind slab 20 cm in depth on an east facing feature at 2400 m. Explosive control work produced numerous avalanches to size 2.5 in north facing terrain immediately lee of ridge crest, these were likely old wind-stiffened storm slabs.
On Monday intense wind loading produced natural wind slab avalanches to size 2 on north facing terrain around 2400 m. Solar radiation (direct sun) also produced natural storm slab and loose wet avalanches to size 2.5 on on a variety of aspects between 1700 and 2600 m.
We received the following information second hand, and all the details may not be accurate, if you have additional information, we would love to hear from you. On Sunday six riders were involved in an avalanche up Doctor Creek. One was stuck, the second went to help and also got stuck, the third rode up the slope to help and triggered an avalanche that buried the three, "up to their faces." The riders credit airbag packs with saving their lives and although one sled was wrecked, the group was able to extricate themselves. The slope was reportedly north facing and failed as a wet slab.
Snowpack Summary
A thin surface crust is now present on all aspects to at least 2000 m. This crust likely goes even higher on south facing aspects, and there may be a bit of preserved cold snow on high elevation north facing features. In the last few days wind slabs 10 to 50 cm in depth have formed in the alpine that sit on a mix of crusts and possibly surface hoar. Continued new snow and wind should fuel their development through the weekend.
Just under the wind slabs there are now a few different crusts, but they have not been problematic.
There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 40 to 90 cm below the surface. This buried crust/surface hoar interface was widely reactive last week, but has not produced any avalanche activity in the last few days. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it fail.
Deeper persistent weak layers from December and January are dormant at this time.
Weather Forecast
A gulf Alaska "mother low" continues to sling smaller lows at the province keeping temperatures cool and offering small amounts of precipitation to the Purcells. There is potential for a stronger system to move into the region this weekend, stay tuned for more details.
THURSDAY: Broken cloud cover, freezing level beginning around 1000 m rising to about 1700 m, light east/northeast wind, 3 to 12 mm of precipitation possible.
FRIDAY: Clear skies in the morning building to scattered cloud cover in the afternoon, freezing level beginning around 500 m rising to about 1700 m, light to moderate west/southwest wind, trace of precipitation possible.
SATURDAY: Broken cloud cover, freezing level holding around 1600 m, moderate to strong southwest wind, 1 to 2 mm of precipitation possible.
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Ongoing winds at ridgetop have formed wind slabs up to 50 cm in depth that are most problematic immediately lee of ridge crest. Up to 12 cm of new snow and northerly wind is expected to add to this problem on Thursday.