Solar Aspects - High pressure remains parked off the coast of California and continues to deflect the storms to the north of the forecast region. This pattern is responsible for ushering in exceptionally warm air mass with daytime temperatures (10 to 20 degrees above average) and overnight lows struggling to fall below freezing in many locations. With the April-like weather, as the snowpack thaws during the day, the free water breaks down the bonds between snow grains and layers within the snowpack, loosing internal strength and cohesion. If the mass of the snow exceeds the snow strength, a Loose Wet or Wet Slab avalanche can occur. The threat of wet instabilities on solar aspects (SE-S-W) will be with us for the foreseeable future as long as the high-pressure ridge remains locked in place off the California coast. With the limited snow coverage, the exposed rocky terrain features can introduce tremendous amounts of heat into the snowpack and cause rapid localized thawing in cirques and gullies. Timing your travels to be out of steep sunny terrain before the snow thaws from the heat of the day is key to avoiding wet instabilities.
Northerly aspects - Patchy persistent weakness continue to lurk within the snowpack with weak faceted sugar layers down about ~30 to ~60cm (12” to 24”) from the surface. Distribution is primarily confined to NE-N-NW aspects from ~9500’ to as high as ~11,500’. Recent test results are somewhat mixed and relatively non-reactive. Despite this persistent weakness, there haven’t been any recent reports of this layer failing but a triggered release is possible, though unlikely. The snowpack on the northerly aspects remains relatively cool but is showing signs of warming, at least at the surface with some mid-elevations beginning to warm and form a thin melt/freeze crust. Otherwise the snow is still somewhat soft in sheltered areas near treeline but aspect and shading is key. In steep sheltered terrain, isolated Loose Dry sloughs may be triggered where the snow is disturbed. Near treeline, where the persistent weakness exists, there is also the potential to encounter small isolated Wind Slabs that were deposited over facets, which could fail if a sufficient trigger is applied.
Below ~9,000’, natural and triggered releases are unlikely due to thin and well-anchored snow coverage (below threshold).
* Caution - Firm snow conditions on southerly aspects in the AM can produce slide-for-life conditions. A minor slide into hazardous terrain can have serious consequences.
