Avalanche Forecast

Issued: Jan 29th, 2019 5:49PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Persistent Slabs and Loose Dry.

ghelgeson, Avalanche Canada

Cariboos.

Watch for fast and shallow loose dry avalanches Wednesday, especially if storm totals exceed 15 cm. Small persistent slab avalanches continue to be a concern at and below treeline where buried surface hoar remains preserved.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

The ridge that has delivered beautiful cold and clear conditions the last few days begins to collapse on Wednesday. High cloud invades the forecast region Wednesday along with light snowfall. The storm really kicks into gear on Thursday and Friday. The cold nature of the flow should keep the snow very dry and light. This pattern continues with dribs and drabs of snow expected as we move through the weekend.TUESDAY NIGHT: Freezing level at valley bottom, light variable wind at most elevations with moderate to strong northwest wind at ridgetop, 1 to 5 cm of snow possible.WEDNESDAY: Broken cloud cover, freezing level near valley bottom, light variable wind at most elevations with strong west/northwest wind at ridgetop, 1 to 5 cm of snow possible.THURSDAY: Overcast, freezing level at valley bottom, light to moderate west/southwest wind, 10 to 30 cm of snow possible during the day with another 10 to 30 cm Thursday night.FRIDAY: Overcast, freezing level at valley bottom, light to moderate west/southwest wind, 10 to 20 cm of snow possible.

Avalanche Summary

No new avalanche activity reported on Monday. On Sunday cornice failures to size 1.5 were observed on north through east facing terrain around 2000 m. Small natural wind slab avalanches to size 1 were reported on east and northeast facing terrain between 2000 and 2300 m.On Saturday a skier triggered a small persistent slab avalanche on an east facing feature at 2000 m, failing on the mid-January surface hoar.

Snowpack Summary

Saturday delivered warmth and wind to the region, followed by 10 to 15 cm of new snow and a very strong wind event on Sunday. This MIN report provides a good description along with some photos that encompass conditions Sunday. The weekend weather left a crust on steep south facing aspects and redistributed quite a bit of snow into potentially deep wind slabs in lee features at and above treeline.Â These wind slabs are likely growing old and tired, and are probably only susceptible to triggering in extreme terrain. 15 to 45 cm of snow continues to consolidate above the mid-January persistent weak layer (PWL). This PWL is made up of large surface hoar that is most prevalent at and below treeline, with enhanced reactivity noted between 1500 and 1800 m. On steep solar aspects this interface presents as a crust, there may be locations where the surface hoar actually sits on the crust.The middle and lower portions of the snowpack are generally well-settled and strong.

Problems

Persistent Slabs

15 to 45 cm of snow sits above a potentially weak interface of surface hoar and crust. The recent warm to cold temperature transition has allowed a more cohesive slab to form above the surface hoar which is most prevalent at and below treeline.

Surface hoar distribution is highly variable. Avoid generalizing your observations.Avoid convex rolls at and below treeline where buried surface hoar may be preserved.Use extra caution around steep open terrain features, such as cutblocks, gullies and cutbanks.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Dry

Cold, dry storm snow falling Tuesday night into Wednesday likely won't bond well to the old surface. These small avalanches are not expected to be much of a problem for sledders, but they could push skiers around, especially in more extreme terrain.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 1

Valid until: Jan 30th, 2019 2:00PM