Any appearance of the strong April sun can initiate a loose wet avalanche cycle. The likelihood of loose wet avalanches increases as temperatures warm through the day and/or if the sun comes out for a prolonged period of time.
Weather Forecast
THURSDAY NIGHT: Mostly cloudy / Light, northwesterly winds / Alpine low -4 C / Freezing level 1000 m.FRIDAY: Mix of sun and cloud / Light, southwesterly winds / Alpine high -3 C / Freezing level 1800 m.SATURDAY: Mostly cloudy with isolated flurries / Moderate, southwesterly winds / Alpine high -3 C / Freezing level 1800 m.SUNDAY: Cloudy with isolated flurries; 0-3 cm. / Light, southwesterly winds / Alpine high -5 C / Freezing level 1500 m.
Avalanche Summary
No new avalanches were reported in this region on Wednesday.On Tuesday, skiers were able to trigger slabs up to size 1.5 in steep, gully features as low as 2200m. Explosives produced avalanches to size 2 and a helicopter remotely triggered a size 1.5 avalanche from 200 m away, these avalanches all started in steep, alpine terrain above 2400 m, mostly on northerly aspects.On Sunday, small (size 1-1.5) wind slabs were reactive to skiers, generally around ridge crests and steep, convex terrain above 2200 m. The most reactive deposits were in immediate lee features, including a size 2 wind slab avalanche remotely triggered from a rocky saddle 10 m away. Overnight Sunday and into Monday, a natural avalanche cycle to size 2 occurred on the western side of the Purcells Forecast region. Storm slab avalanches to size 2, with crowns 20-50 cm deep were observed in alpine terrain on all aspects.
Snowpack Summary
5-25 cm of recent storm snow sits on a melt-freeze in most locations, except for northerly aspects above 2100 m. where the old snow surface remained dry and the recent snow sits on small surface hoar (weak, feathery crystals) in isolated locations. Southwest winds formed wind slabs in lee features below ridgetops. The depth of the snowpack deteriorates rapidly below 1200 m.Weak facets (sugary grains) remain at the bottom of the snowpack in the alpine creating a low likelihood, high consequence scenario that would likely require a large trigger to initiate an avalanche. Steep, rocky areas with a shallow or highly variable snowpack are the most likely places to trigger a very large avalanche on this layer.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.