Avalanche Forecast
Issued: Jan 16th, 2023 4:00PM
The alpine rating is Persistent Slabs and Storm Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeAvalanche hazard may seem to be improving under foot; however be mindful that deep instabilities remain. Hurley seems to be the bulls-eye for a poor snowpack structure and it's reflected in the danger ratings. Uncertainty is best managed through conservative terrain choices.
Summary
Confidence
Moderate
Avalanche Summary
The snowpack structure, with its mid and basal problems, mean reports remain relevant, even if several days old.
No new avalanche reports from Sunday.
On Saturday Hurley was the bulls-eye for avalanche activity on persistent weak layers in the middle and bottom of the snowpack. Surface hoar on the Christmas crust was releasing naturally, intentially, remotely, and with direct human triggers on gentle slopes near treeline (1800 to 1900 m) with crowns up to 80 cm thick. Some natural avalanches size 3 to 3.5 and ran full path from the alpine to valley bottom.
Additionally Storm Slabs size 2 to 3 were reported releasing at the bottom of the storm snow. One large wind slab (size 2.5) involved the weak facets at the bottom of the snowpack.
On Friday, snowcats remotely triggered numerous size 2.5 persistent slab avalanches on surprisingly low angel terrain from up to 150 m away. Avalanches occurred on a crust covered by surface hoar found up to 1900 on north and easterly aspects. See MIN for good photos and more details.
Thanks for the observations and please continue to post your reports and photos to the Mountain Information Network. It is really helpful for forecasters!
Snowpack Summary
The region's generally weak snowpack structure remains.
Last week's 20-30 cm of snow and southerly winds means wind slabs may linger. Below 1900 m there was a mix of rain and snow which is freezing into a crust.
Mid-pack: 50 to 70 cm down is a crust formed in late December. Between 1900 and 1700 m surface hoar can be found above this crust which was reactive with the new snow load on Friday. This crust varies in thickness throughout the terrain and elevation.
Lower-pack: There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack. Snowpack depths around treeline are about 150-180 cm deep. The snowpack below treeline is very shallow and faceted.
Weather Summary
Monday Night: Cloudy. Dry. Light southwest wind. Treeline temps around -5 C.
Tuesday: Nil to a few cm of new snow. Mainly cloudy. Freezing level near 1200m. Mostly cloudy. Treeline temperatures -2 to -5 C. Light to moderate southwest wind.
WednesdaySouth wind strengthens to moderate, strong at high elevations. 5 to 10 cm of new snow. Freezing level briefly rising to near 1300 m. Mostly cloudy. Treeline temperatures around -5 C.
ThursdayMix sun and cloud. Dry. Cooler with treeline temps around -10 C. Light west wind.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
Problems
Persistent Slabs
A widespread crust formed in late December is found down 50 -70 cm. In many areas, this crust has slowly been healing however in isolated areas preserved surface hoar crystals overlie this layer and have recently resulted in large avalanches. This weak layer has been most reactive in the central and northern parts of the region, particularly around the Hurley and Birkenhead areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
20-30 cm of storm snow and southerly winds have built storm slabs in lees at higher elevations. Watch for wind-affected areas where deeper pockets feel more cohesive and could remain reactive to human triggering.
Be aware that slab avalanches could step down to deeper layers producing larger-than-expected avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 17th, 2023 4:00PM