Forecast snowfall amounts for Sunday night are highly variable across the region. Pay close attention to how much snow falls in your area, and be prepared to stick to conservative terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Sunday
Weather Forecast
SUNDAY NIGHT: 15-30cm of new snow with highest accumulations falling in the southwest of the region / Strong southwest ridgetop winds / Freezing level at about 1500mMONDAY: Mix of sun and cloud / Moderate southwest ridgetop winds / Freezing level at about 1500mTUESDAY: 10-20cm of new snow falling mostly in the early morning - easing by mid day / Strong southwest ridgetop winds / Freezing level at about 1400mWEDNESDAY: Mix of sun and cloud with isolated flurries / Light southwest ridgetop winds / Freezing level at about 1200m
Avalanche Summary
At the time of publishing on Sunday, we had a few new reports of natural wind slab avalanches up to size 2.5 in steep alpine terrain. Some of these occurrences are thought to have been cornice-triggered. At treeline where there was considerably less wind, naturally triggered wind slabs were observed in the size 1-1.5 range. Increasing southwest winds and moderate amounts of new snow on Sunday night will spark a new round of wind slab activity in higher elevation lee terrain. Periods of sun on Monday may also promote loose wet avalanche activity on steep sun-exposed slopes, especially in spots where new snow is exposed to solar radiation for the first time.
Snowpack Summary
On Sunday night, moderate amounts of new snow are expected to fall, and strong southwest winds are expected to form deep new wind slabs in lee features at treeline and in the alpine. The new snow will overlie wind slabs and settling storm snow which fell throughout the weekend. About 40-70 cm below the surface, you'll likely find a melt freeze crust which exists in most places except for in high elevation shaded terrain. Although there seems to be a reasonable bond between the crust and the overlying snow, it could be a potential failure plane, especially if temperatures are warm or solar radiation is strong. Surface hoar buried in early January now lies up to 200cm below the surface, and has become unlikely to trigger.
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.