Watch for reactive new wind slabs formed (and forming) in leeward terrain features at treeline and above. Be aware of a trickier hazard scenario involving buried weak layers in the northern tip of the region.
Another, weaker frontal system will add a bit to new wind slabs on north and east aspects. Older, more stubborn buried slabs may exist on all aspects in steep high elevation terrain.
Persistent slab avalanches remain possible in the northern tip of the Purcells where there has been recent avalanche activity on a 40-80 cm deep layer of surface hoar, facets, and/or crusts (see Avalanche Summary).
SATURDAY NIGHT: Cloudy with isolated flurries. Light southwest winds.
SUNDAY: Cloudy with scattered flurries bringing about 5 cm of new snow, continuing overnight. Light to moderate southwest winds, becoming strong in the alpine. Alpine high temperatures around -6 with freezing levels to 1400 metres.
MONDAY: Mainly sunny. Light variable winds. Alpine high temperatures around -6 with freezing levels to 1500 metres.
TUESDAY: A mix of sun and cloud. Light variable winds shifting west. Alpine high temperatures around -6 with freezing levels to 1500 metres.
Warm sunny weather between Wednesday and Friday resulted in a widespread cycle of wet loose avalanches on sun-exposed slopes. Photos from this flight over the southwestern Purcells shows so some very large wet avalanches that ran to valley bottom. Cooling temperatures have since worked to stabilize this problem.
Over the past week there have been several notable reports of large human triggered persistent slab avalanches in the Dogtooth Range and Quartz Creek area, including:
While in most parts of the Purcells the main concern over the weekend is wind slabs (both old and new), backcountry travelers in the northern tip of the region should be extra cautious about the lingering persistent slab problem in this area.
5-15 cm of new snow over Friday night accumulated above moist and crusty interfaces that formed during the recent warm up. Some deeper accumulations can be expected in lee terrain features. High shaded terrain will have a mix of soft snow and some old buried wind slabs.
Persistent weak layers have been most active in the northern end of the Purcells where a buried layer of surface hoar that formed in late January is 40-80 cm deep and an older surface hoar layer is 60-120 cm deep at treeline. These layers may exist as a combination of facets and crusts at other elevations. Recent observations suggest these layers have been less problematic as you move further south.
Steep rocky areas where the snowpack is thin likely have additional weak layers near the base of the snowpack.
