Avalanche Forecast

THURSDAY NIGHT: Cloudy with isolated flurries and a trace to 5 cm of new snow. Light southwest winds.

FRIDAY: Cloudy with increasing flurries bringing 5-10 cm of new snow, continuing overnight. Moderate to strong southwest winds. Alpine high temperatures around -5 with freezing levels rising to 900 m.

SATURDAY: Cloudy with continuing flurries bringing about 5 cm of new snow and new snow totals to 15-30 cm. Snowfall increasing overnight. Moderate to strong south winds. Alpine high temperatures around -5 with freezing levels rising to 1300 m.

SUNDAY: Cloudy with flurries bringing another 10-15 cm of new snow and new snow totals to 40-60 cm. Moderate southwest winds easing over the day. Alpine high temperatures around -5 with freezing levels to 1500 m.

A few more signs of the storm snow above our Christmas interface reacting as a slab turned up on Wednesday in the Monashees south of Revelstoke. A few ski cuts produced size 1 soft slabs, with one ski cut on a regularly performing feature producing a size 2 avalanche (large).

On Monday, a couple skier triggered storm slab avalanches up to size 1.5 were reported on north and south aspects at treeline in the same part of the region.

There have been numerous recent reports of dry loose avalanches(sluffs) running surprisingly fast and far below treeline.

Watch for avalanche danger to trend upward again on Friday night as new snow accumulates, new slabs form, and a fresh load tests layers deeper in the snowpack.

In some areas a few cm of new snow may overlie small surface hoar or a thin ice crust (noted in the Monashees near Revelstoke and around Galena Pass). Otherwise, the skiff of new snow adds to 30-50 cm of accumulated snow since Christmas day, which overlies a mixture of faceted old surface snow and small surface hoar.  

This predominantly low density snow now forming the upper snowpack is most likely to be reactive in wind affected areas where it has been redistributed and stiffened into a slab. However, the two interfaces discussed above will be important to watch as new snow piles up over the weekend.

Two persistent weak layers buried in early/mid Dec. are now 80 to 150 cm below the surface. The form and distribution of these layers are HIGHLY VARIABLE and have created conditions that can vary significantly from one valley to the next. The first layer down around a metre has been primarily reported as small surface hoar. 

The next layer has been reported as a thin freezing rain crust, surface hoar, or thick rain crust depending on elevation and location. As a result, diligent investigation of the snowpack is required to get a handle on local conditions. Forecast snowfall for the weekend may reignite avalanche activity at these deeply buried interfaces.

• Uncertainty is best managed through conservative terrain choices at this time.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Be especially cautious as you transition into wind affected terrain.
• Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.