Another sunny day is expected Saturday, with freezing levels reaching mountain top. Avalanche hazard will start as Low, but will quickly deteriorate with daytime warming and strong solar imputes —start and finish early.
Click the link for advice on dealing with spring conditions
As the warming trend continues, more incidents of cornice failures may occur. A large cornice failure may trigger the persistent layers in the slopes below. Consider and manage your exposure to terrain overhead.
An 80 cm thick midpack slab sits over a weaker, facetted base. On most slopes, recent sun crusts and a buried March 27 rain crust cap this slab, adding strength as long as it is frozen. We suspect it would take a large trigger, like a cornice or intense solar input, to trigger these deeper layers.
Monitor daytime temperatures and solar input, as the likelihood of avalanches will increase over the day. Start and finish your tour early to avoid this problem.
Solar heating contributed to increased avalanche activity predominantly on South and West aspects Friday. By mid afternoon we were seeing the crust break down which resulted in a loose wet avalanche cycle to size 2. We also received reports of cornice releases.
No avalanches reported on the persistent weak layer since the last warm-up on April 18th, when there were 2-3 size 2.5 avalanches off Pilot Mtn.
Hard surface crusts exist to ridgetops in the AM on solar aspects, and at treeline and below on northerly aspects. The top 10-20cm was moistening at the ski hills in the afternoon.
North alpine slopes hold 5 - 15 cm of dry snow over firm surfaces. The March 27 crust is 30-70 cm deep and extends to about 2500m on North slopes, reaching ridge top on solar aspects.
Below the settled mid-pack, weak facets and depth hoar remain.
A ridge of high pressure will remain in place on Saturday, bringing clear skies and strong solar input. Freezing levels will rise to mountain tops, with valley bottom temperatures reaching up to +15°C. On Sunday, cloud cover will increase, accompanied by light precipitation as a low-pressure system moves into the forecast region.
