More snow Monday night will add to the storm slabs at upper elevations. These may become more reactive as the day warms or if the sun appears on Tuesday. Also watch for loose, wet activity on sunny and lower elevation slopes.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
TONIGHT: Mostly cloudy, flurries. Accumulation 10-15 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1000 m.TUESDAY: Mostly cloudy, light flurries. Accumulation up to 3 cm. Ridge wind moderate to strong, west. Alpine temperature near -6. Freezing level 1700 m.WEDNESDAY: Mix of sun and cloud. Ridge wind light, southeast. Alpine temperature near -4. Freezing level 1800 m.THURSDAY: Increasing cloud. Ridge wind light, southwest. Alpine temperature near -1. Freezing level 2200 m.
Avalanche Summary
Sunday there was a report of a near miss for skiers who triggered a size 2 wind slab on a north aspect at treeline in the northern part of the region. While in the northwestern part of the region saw a warming-induced, natural avalanche cycle up to size 3 on large alpine features in the recent storm snow.Saturday, explosive control work in northern parts of the region produced several storm slab releases size 2-2.5 on predominantly treeline to alpine, west aspects with wide propagations up to 200 m. And ski cuts produced size 1-1.5 results on cross-loaded features.Friday several skier-triggered, size 1.5 wind slab releases were reported on north aspects at 2300 m. As well as a few solar-triggered storm slab releases (size 1.5) on steep, unsupported. west-facing features at 2200 m.Wednesday there was a report of an icefall-triggered size 1.5 wind slab (50 cm deep and 50 m wide) on a north aspect at 2400 m.
Snowpack Summary
About 20 cm on new snow overlies a crust on all aspects to at least 2000 m (and possibly higher on south-facing slopes), while 30-40 cm can be found at higher elevations (and up to 60 cm in some areas in the northwest of the region). Below 2200 m this new snow has thin surface crust, breaking down to moist or wet snow in the afternoons.Within the upper snowpack there a now several buried crusts with only the mostly recently buried posing a concern with the recent storm snow..There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 50 to 90 cm below the surface. This buried crust/surface hoar interface is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think step-down from a surface avalanche or cornice collapse)Deeper persistent weak layers from December and January are considered dormant at this time.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.