Continually assess for wind slabs as you move through the terrain. Small pockets of wind slab have been reactive to skier traffic and natural triggers.
Variable winds over the past few days mean that wind slabs can be found on all aspects. Most recently natural wind slab avalanche activity has been reported on westerly aspects. Periods of strong winds on the weekend may have formed wind slabs further down the slope than usual.
There are two layers of concern in the upper and mid pack. These layers are generally made up of facets and surface hoar but on south aspects a crust can be found. These layers are most likely to be triggered on sparsely treed slopes at treeline and below. These layers were reactive to skier triggering in the Norns and Rossland region last week.
On Tuesday, natural and skier triggered dry loose avalanches were reported to size 1 in steep terrain.
On Sunday and Monday, several natural wind slab avalanches were observed to size 2.5 on westerly aspects between 1800 and 1400 m. These avalanches may have been triggered by cornice fall or strong easterly winds on Saturday night. A skier accidental, size 1.5, wind slab avalanche was reported on a northeast aspect at 1900 m. Check out this MIN from Saturday showcasing the current wind slab problem.
Last week, several skier triggered persistent slab avalanches, up to size 2.5, were reported in the Norns and Rossland region. Many of these avalanches failed on weak layers from February and January and occurred at treeline. Though activity has tapered off on this layer it could still be reactive to large triggers.
40-60 cm of storm snow has been redistributed by shifting winds into wind slabs on all aspects at treeline and above. This storm snow sits over a wind affected layer at all elevations. On open solar aspects, a melt-freeze crust covers the surface.
A layer of surface hoar can be found on shaded slopes, and a sun crust on sun affected slopes buried 40 to 70 cm deep. Another layer from January is buried up to 50 cm below this. These layers were reactive in the Rossland region this week.
The lower snowpack includes a layer of weak sugary crystals near the ground. These facets are slowly gaining strength and have not produced recent avalanche activity. We continue to track the layer and watch for any signs that it could wake up and produce very large avalanches.
Wednesday Night
Mainly clear with cloudy periods. Southeasterly winds 15-25 km/h. Treeline temperatures, low of -9. Freezing levels drop to valley bottom.
Thursday
Mainly cloudy with sunny periods. Southeasterly winds 10-25 km/h. Treeline temperatures, high of -8. Freezing levels 800 m.
Friday
Cloudy and scattered flurries, 5-7 cm accumulation. Southeast winds 25-40 km/h. Treeline temperatures, high of -7. Freezing levels remain at valley bottom.
Overnight flurries continue 2-5 cm accumulation. Winds switch to the southwest 40-60 km/h.
Saturday
A mix of sun and cloud with isolated flurries, trace accumulation. Southwesterly winds 10-25 km/h. Treeline temperatures, high of -5. Freezing levels 1300 m.
More details can be found in the Mountain Weather Forecast.
