Regions
Northwest Inland.
Confidence
Fair - Due to variable weather conditions
Weather Forecast
A continued low over the Gulf of Alaska will whirl a series of convective systems through the southern part of the province, bringing light precipitation to the North West regions. Friday: Snow amounts 3-10 cm. Ridgetop winds light from the SW. Alpine temperatures near -3. Freezing levels 1200 m then falling to valley bottom at night. Saturday/Sunday: The weekend will continue with quite the mixed bag of unsettled, spring-like convective weather. Expect bands of fast moving clouds, light precipitation, and periods of sun in the afternoons. Freezing levels 800 m during the day, falling to valley bottom at night. Ridgetop winds will be light - moderate from the SE-SW.
Avalanche Summary
Reports from Wednesday indicated loose, solar induced sluffing and pinwheeling below 1500 m. On Tuesday a natural cornice fall triggered a size 2 slab avalanche on the slope below. This occurred on a NE aspect.
Snowpack Summary
Moderate-Strong SE-S winds continue to build wind slabs. They may be found in unusual places, lower on the slope or in open areas below treeline. Windward aspects may become wind pressed, and even scoured. North aspects at higher elevations hold dryer, low density snow in the upper 20 cm. Spring-like conditions exist and crusts have formed on solar aspects at all elevations, becoming moist under sunny skies. Melt-freeze conditions exist @ treeline on all aspects. Below treeline has remained moist, with no recovery below 1500 m. The mid-pack is well consolidated. The mid February persistent weak layer, comprised of spotty surface hoar, facets and crusts, is buried 80-120 cm below the surface. No recent activity has been reported on this interface. It most likely needs a large trigger on a specific spot. If an avalanche occurs on this weak interface it will be very large and destructive. Below this the snowpack is well settled and strong. Cornices in the area are reported to be very large. Cornice failure could trigger an avalanche on the slope below.
Problems
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.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.