Summary
Confidence
Fair - Freezing levels are uncertain on Monday
Weather Forecast
High cloud moved across the region on Sunday afternoon that limited the extent of solar warming, but trapped warm air beneath the cloud layer that raised the alpine temperatures to near zero. The freezing level is expected to drop down to near valley bottom by Monday morning. Unsettled weather producing cloud and variable southerly winds during the day Monday. The wind is expected to increase Monday evening and become strong from the southwest by Tuesday evening. The freezing level is forecast to rise to about 1400 metres on Monday and only drop down to about 1200 metres Tuesday morning. Precipitation is expected to begin Tuesday afternoon and become heavy overnight into Wednesday morning.
Avalanche Summary
Some snowballing and sluffing on solar aspects in the afternoon on Saturday. One report of a remotely triggered large avalanche on a north aspect of Mt Tupper in Glacier National Park. The group of ski tourers had a large settlement on a ridge, and the adjacent slope failed down about 150 cm. Large remotely triggered avalanches have become less frequent, but they are occurring about every second day.
Snowpack Summary
Wind slabs in the alpine and at treeline are becoming less reactive. A melt-freeze crust exists from valley floor into the alpine on solar aspects. A key concern is a persistent weak layer of buried surface hoar from mid-February that is buried 1-2 m deep. Snowpack tests give sudden "pops" results on this layer in some areas, indicating the ongoing potential for very large avalanches. Because the layer is so deeply buried, it's unlikely to fail without a large trigger (e.g. cornice fall or explosive). However, there's always the chance of someone stumbling across a sweet spot, particularly in shallow snowpack areas. Solar warming could also destabilize the overlying snowpack, with the potential for step-downs or cornice triggering on this layer.
triley,
Avalanche Canada
