South Columbia

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.

Moderate - Forecast snowfall amounts are uncertain on Sunday

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

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.

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.