The first sustained warmup of spring is finally here. Surface instabilities and cornice hazards should be firmly on your radar as you travel. Expect stability to deteriorate over the day.
Summary
Confidence
Moderate -
Weather Forecast
Monday: Sunny. Light south winds. Freezing level to 2400 metres and climbing overnight. Alpine high temperatures around +1.Tuesday: Mainly sunny. Light south winds. Freezing level to 3000 metres with alpine high temperatures around +5. Weak overnight cooling.Wednesday: Sunny. Light northwest winds. Freezing level to 3500 metres with alpine high temperatures around +8. Weak overnight cooling
Avalanche Summary
Decreasing traffic in the mountains has led to limited avalanche observations over the past few days.A few natural storm and wind slab releases were observed on Thursday, ranging from size 1-2.5. One of these was a size 2 slab triggered by a loose wet avalanche while the 2.5 wind slab was triggered by natural ice fall on a north aspect at 2200 metres. It featured a 45 cm crown fracture.Reports from Wednesday included an observation of a natural size 2 cornice release from a north aspect in the north of the region. Numerous natural loose wet avalanches were also observed on sun-exposed aspects in the Monashees.Tuesday's reports showed numerous small (size 1) storm slabs releasing both remotely and with ski cutting. Crown fractures were in the 35-40 cm range and activity was observed at all elevations and on all but west aspects.Observations from just over a week ago showed a pattern of heightened cornice failure activity.Looking forward, a period of increasing warming, full sun, and warm overnight temperatures will be maintaining elevated chances of cornice and loose wet avalanche activity.
Snowpack Summary
About 15-20 cm of new snow has been blown into wind slabs on a variety of aspects due to variable but predominantly southwest strong winds. The wind-affected snow overlies a melt freeze crust found on the previous surface on all but north aspects above about 2200 metres. Below it, About 70-100 cm of mostly settled storm snow overlies another supportive crust with similar distribution to the upper crust.Within the upper snowpack there are now a few different crusts with the shallowest of these (down 30-50 cm) now a limited concern as warm temperatures have promoted settlement in the upper snowpack.With warm daytime temperatures and poor overnight recovery of cold temperatures, there remains some lingering concern around the mid-March persistent weak layer in the alpine where it is found 80 to 120 cm below the surface. This buried crust/surface hoar interface was widely reactive but is likely trending towards dormancy. It should be kept in the back of our minds for its capability to produce large avalanches should it be triggered with a heavy load such as a snowmobile or cornice collapse.Deeper persistent weak layers from December and January are considered dormant at this time.
cgarritty,
Avalanche Canada
