Avalanche Forecast
Issued: Mar 16th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Persistent Slabs.
PW,
Avalanche Canada
We're doing avalanche control on Mt. Whymper, Friday March 17. Please avoid recreating in the Mt. Whymper avalanche control area. Click the LINK for location details.
Thank you.
Summary
Confidence
Avalanche Summary
We've had numerous reports of skier triggered avalanches in the last 36h. Ranging in size from 2-3, failing in the basal facets. These avalanches have largely been triggered from thin areas in the snowpack.
There have been multiple reports of natural avalanches, up to size 3, also failing in the basal facets. Mt. Norquay ski hill also reported a size 4 avalanche on Mt. Brewster in the last 48h.
As the afternoons warm up, we are expecting to see continued activity on these persistent weak layers.
Snowpack Summary
15-30 cm's of recent snow has fallen on a freshly buried (March 12) layer of surface hoar, facets and sun crust. Snow profiles are producing sudden results on this layer. Sun crusts at or near the surface have been reported in isolated areas below 1600m. The mid-pack comprises various Jan crust's that are now down 60-100 cm. The weak Nov. 16 basal facet layer is down 50-120 cm producing sudden results in snowpack tests. The basal facets have become more triggerable with the additional load and warmth. Cornices are also quite large and will also be affected by solar inputs.
Weather Summary
The high pressure that we have been experiencing will stick around through Friday and into the weekend, with mainly sunny skies persisting.
Friday's alpine high will be -10 and valley bottoms will be as warm as +5, with freezing levels set at 1800m. Winds will continue to be light in the morning, but will creep up to 40 km/h by the afternoon out of the south/southwest.
Saturdays weather looks to be quite similar, however temperatures could be even warmer.
For a more detailed forecast click here.
Terrain and Travel Advice
- Uncertainty is best managed through conservative terrain choices at this time.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Storm Slabs
Surface snow from the past few days may settle into a slab over a new weak layer buried on March 12. We are currently assessing this interface throughout the region. Avalanches may release from solar inputs Thursday. These avalanches may start small but then trigger a deeper layer and become large.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
We have seen increased activity on this layer. Multiple parties have remote triggered this problem from thin areas in the snow pack. Give careful consideration to the slopes overhead as large avalanches may run well into the runout zone or into lower-angle terrain. Avoid big terrain features and be especially cautious in thin or rocky areas, where triggering is more likely. The weak depth hoar at the bottom of the snowpack inspires little confidence and will continue to wake up with each new storm or warming event.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Three persistent weak layers formed in January are down 60-110 cm. Buried sun crusts on steep solar slopes present the greatest concern for triggering, however, weak facets and isolated surface hoar can be found on the same interfaces on shaded aspects.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 17th, 2023 4:00PM
