It's a great time to get out! Easy travel on firm surfaces (crampons helpful!) with 5 - 15 cm on high due north aspects. Travel in the early morning hours and watch for sun-triggered wet loose avalanches. Spring Conditions - The hazard is expected to be Low in the cold mornings and rise in accordance with the degree of warming.
Enjoy!
As the days progressively warm with solar input and temperatures, from Thursday to Saturday, there may be more incidents of cornice failures. 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. We suspect it would take a large trigger, like a cornice or a human in a very steep, thin area, to get this going.
Monitor daytime temperatures and solar input as this problem may develop over the day. Start and finish your tour early to avoid this problem.
Tuesday, Sunshine patrol reported observing a distant cornice failure on the Monarch in the Sunshine backcountry. They estimated it was not larger than a size 1.5, and that it was unlikely to have triggered a slab.
Otherwise, no avalanches observed or reported on Tuesday or Wednesday.
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 on steep solar aspects and at treeline and below.
On north alpine aspects, 5 - 20 cm of dry snow over firmer surfaces. Off due north, some alpine slopes may have a new surface thin crust capping the 5-10 cm of snow from a few days ago.
The March 27 crust is 30-70 cm deep and extends to about 2500m and to the ridge top on solar aspects.
Below the settled mid-pack, weak facets and depth hoar at the ground remain.
Progressively warmer over Thursday through Saturday with clear skies and light SW wind. Despite the warming trend for temperatures at 3000 m over the next few days, the freezing levels drop to the valley bottom for Wednesday and Thursday night. Daytime freezing levels rise to 2500 m on Thursday, 2800 m on Friday, and about 3000 m on Saturday.
See the attached weather table for more on temperatures and wind.
