Avalanche Forecast
Issued: Mar 5th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
istorm,
Avalanche Canada
When the highway to White Pass reopens start cautiously and use an "Initial Assessment" mindset to figure out conditions. If you're diverted to a place like the Wheaton Valley be mindful of its weaker snowpack structure and choose terrain accordingly.
Summary
Confidence
Moderate - The snowpack structure is generally well understood. Uncertainty is due to the limited number of field observations.
Weather Forecast
FRIDAY NIGHT: A few flurries. Alpine temperatures -10 C. Moderate south to southwest wind (25 to 45 km/hr).
SATURDAY: A few flurries. Alpine temperatures -10 C. Moderate southwest wind (25 to 40 km/hr).
SUNDAY: Wind shift to light north to northeast. The shifting wind allows for a brief clearing and slightly drier, with a few flurries. Alpine temperatures a few degrees cooler around -12 C.Â
MONDAY: Ridge continues to build and the drying trend continues, with some sun likely, light to moderate northwest wind, alpine temperatures around -15 C.
Avalanche Summary
With the South Klondike Highway closed, for White Pass avalanche summary, read Wed March 03 forecast.
With recreational traffic diverted to places like the Wheaton, our field team did similar this week. 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.
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
For White Pass snowpack structure read Wed March 03 forecast.
With the South Klondike Highway closed allow me to say a few words about the Wheaton Valley snowpack. The Wheaton's continental snowpack is the kind of thing you'd find around Jasper or K-Country. 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, in the old days, was compared to the crazy mother-in-law who lives in your basement and you never know when the relationship is going to go sideways. Let me repeat, 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.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
Problems
Persistent Slabs
In colder drier areas -- like the Wheaton -- the entire snowpack could be in play because the weakness extends to the ground. Recent avalanche 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
Wind Slabs
Assuming there's still snow available for transport, the windshould be building new wind slabs to the lee of the wind (north through east slopes) and in crossloaded features.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 6th, 2021 4:00PM
