Avalanche Forecast
Issued: Mar 8th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
MBender,
Avalanche Canada
If you are heading to White Pass now that the highway has reopened, adopt a cautious mindset while you figure out conditions. If you are headed to the Wheaton Valley, be alert to its weaker snowpack structure.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
MONDAY Night: Mainly clear skies, light to moderate northeast wind, alpine temperature around -15 C.
TUESDAY: Sunny, light northerly wind, alpine temperature -7 C.Â
WEDNESDAY: Mix of sun and cloud, light southwest wind, alpine temperature -10 C.
THURSDAY: Mainly cloudy with flurries, moderate southwest wind, alpine temperature -9 C.
Avalanche Summary
There was an widespread avalanche cycle mid last week in White Pass that coincided with the road closure. We have no current information on avalanche activity.
With recreational traffic diverted to places like the Wheaton, our field team did similar last week and into the weekend. They observed up to size 2.5 avalanches, especially on south facing slopes, starting high on ridges and rolling well into and through the trees. See a couple of MIN posts here and here.
The term 'Wheatonesque whumpfs' is worth holding onto. Remember that a whumpf is an avalanche that tried, with one key ingredient is missing -- slope angle. Whumpf the right terrain and you've converted it into the real thing, hopefully it's not rolling down ontop of you.
Snowpack Summary
A heavy dose of snow early to mid last week closed the highway due to avalanches hitting the road. We have since not been able to get updates on conditions. Avalanche activity during the storm suggests there were largely storm and wind slab problems during and immediately after the stormy period. Once the road is open again and we can get our field team up there we will update snowpack conditions.
If White Pass is still closed and you are heading to the Wheaton Valley, there is likely a crust that has formed on the surface on steeper sunny aspects with recent sunshine. The Wheaton's continental snowpack is the kind of thing you'd find around Jasper or Kananaskis Country in the Rockies. It's a weak snowpack dominated by sugary facets and depth hoar, the icing is either layers or a fat cap of harder cohesive slab. It's an untrustworthy structure that requires really good terrain selection and travel habits, or a healthy dose of luck.
Terrain and Travel
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- Make observations and assess conditions continually as you travel.
- Start on smaller terrain features and gather information before committing to bigger terrain.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Problems
Wind Slabs
Assuming there's still snow available for transport, the wind should be building new wind slabs to the lee of the wind and in cross-loaded features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This problem is relevant to the colder drier areas, like the Wheaton, where the entire snowpack could be in play because the weakness extends to the ground. Recent avalanches were reported to have run far through the trees. Read the snowpack section of this forecast. As you approach avalanche terrain, whumpfs are a critical sign that the snowpack is unstable & primed.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 10th, 2021 4:00PM
