Wind slabs are expected to be the primary concern on Monday. The wind is expected to switch directions so wind slabs should be expected on all aspects in exposed terrain.
New wind slab formation is expected on Monday as the wind switches direction and blows from the northeast. Reactive wind slabs should be expected on all aspects in exposed terrain.
An early season crust at the base of the snowpack has shown reactivity in the southeast corner of the forecast region. While this layer likely needs a heavy trigger like a cornice collapse or smaller avalanche stepping down, human triggering may still be possible on thin rocky slopes in this part of the region.
On Saturday, a report on social media suggests there was an human triggered avalanche in the old Azu area outside Powder King but details on the avalanche are very limited. On Friday, the North Rockies field team reported shooting cracks and were triggering small slabs with ski cuts near treeline in the Pine Pass area.
On Monday, wind slabs are expected to remain reactive to human triggering and natural wind slab avalanches are possible. The wind is expected to switch directions so wind slabs should be expected on all aspects. A lingering deep persistent problem still exists in the south of the region but appears to be gaining strength. This deep weakness is likely creating a low probability/high consequence scenario.
An Arctic ridge of high pressure brings cold and dry conditions to the region for the next few days.
Sunday Overnight: Partly cloudy with a chance of isolated flurries, light to moderate S winds, treeline temperature around -15 °C.
Monday: A mix of sun and cloud with a chance of isolated flurries, moderate to strong NE winds, treeline high around -15 °C.
Tuesday: Mainly sunny, light to moderate NE winds, treeline high around -20 °C.
Wednesday: Mainly sunny, light to moderate SW winds, treeline high around -16 °C.
On Friday and Saturday, up to 20 cm of new snow was reported bringing the weekly storm snow accumulation to 40-70 cm. This new snow came in with strong winds from the southwest which formed highly reactive slabs in wind exposed terrain. On Monday, the wind is expected to switch directions and wind slabs should be expected on all aspects. Below the past week's storm snow, some surface hoar had been observed in sheltered areas at and below treeline but this appears to be isolated and has not been reactive in recent days.
The lower snowpack consists of a series of early season crusts. Cold temperatures will have promoted faceting around these crusts. Shallow alpine slopes along the eastern side of the Rockies towards Jasper may have weaker, faceted snow near the ground.
Snowpack depths at treeline range from 60cm-200cm, with the shallower value mainly on the eastern side of the range. The alpine snowpack ranges from 150cm-200cm.
