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 and synoptic systems into the southern part of the province, bringing remnants of those systems to the northern regions. The bulk of the precipitation will arrive Thursday-Friday, with continued bands of fast moving clouds, light precipitation and sunny breaks later into Saturday. Thursday: Snow amounts near 5 cm. Ridgetop winds strong from the South. Alpine temperatures -4, freezing levels near 1200 m during the day then dropping to valley bottom at night. Friday: Snow amounts 5-10 cm. Ridgetop winds moderate from the South. Freezing levels valley bottom. Saturday: Occasional light flurries and cloud cover. Sunny breaks expected with intense solar radiation during those times. Freezing levels are expected to be near 600 m.
Avalanche Summary
Reports from Tuesday indicated small loose, solar induced sluffing. A natural cornice fall triggered a size 2 slab avalanche on the slope below. This occurred on a NE aspect. Other operations have reported no new avalanche activity through their tenures.
Snowpack Summary
Wind slabs will continue to build. 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 below treeline on all aspects. Below this sits a well consolidated, settled mid pack. 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.
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.
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.