Avalanche Forecast

While Deep Persistent Slabs are very difficult to trigger, the resulting avalanche could leave little chance of survival. Persistent weak layers have been the cause of avalanche fatalities or serious injuries for the past month. Recent test results and avalanches show that these layers are still present, though getting harder to trigger. The best way to stay safe is to limit your exposure to large avalanche paths. Stay out of large start zones and complex avalanche paths.

You may see roller balls and small Loose Wet avalanches running on polar aspects if light rain falls. Recent melt-freeze cycles have left some snow surfaces hard and slick. It may be difficult to stop a fall on these slopes while they are still firm. Avoid traveling near or under areas with glide cracks and stay away from large cornices.

Expect mild temperatures and increasing high cloud cover for Wednesday with very light rain/snow possible and a snow line near the top of the below treeline band. Loose Wet avalanches should not pose significant hazard as the areas potentially impacted by rain hold very shallow dry snow in most areas. 

Two days of warm, spring-like weather produced minimal Loose Wet avalanche activity and a supportable crust in many sun-affected locations. This followed a dusting of light snow on Saturday and Sunday on the tails of another warm, sunny stretch at the end of the work-week. Many sunny slopes have very hard stout crusts in the top foot of the snowpack. Northerly, shaded slopes around 4,000 ft and above are staying soft and dry and reports indicate the potential for small loose dry avalanches on steeper slopes at elevation.

Immediately below this most recent crust you may find unfrozen wet grains. Most observations indicate strong layers of dry snow intermixed with various melt freeze crusts throughout the upper snowpack. In isolated locations, thin buried persistent weak layers have been reported. You are most likely to find a buried persistent weak layer in shaded locations (see a recent public observation), at higher elevations, and/or in terrain slightly east of the Cascade Crest. 

A more widespread persistent layer continues to be found 3-6 feet below the snow surface. A thin layer of weak sugary facets have been observed just above a stout crust (2/8). While some Compression Test and Extended Column Tests may show results on this deep weak layer, many will not. Deep Tap tests and Propagation Saw tests will yield the most reliable results. While snowpack tests are good for demonstrating the presence of a weak layer, they are not a decision-making tool to determining whether or not a slope is safe.

Observations

Stevens

NWAC forecaster Josh Hirshberg reported up to 4 inches of new snow in the Stevens backcountry on Monday. On sun-exposed slopes, he observed melt forms in the top 2 feet of the snowpack. The 2/13 layer (about 3 feet below the surface) had received liquid water and transitioned to melt forms, as well.

Snoqualmie

On Tuesday morning, Alpental Pro Patrol reported a firm crust developing on the surface which was still breakable in some locations.

NWAC professional observer Jeremy Allyn traveled in the Alpental Valley Saturday. Jeremy found unsupportive snow on steep sunny slopes by afternoon. He observed many loose wet avalanches up to D2 from the past few days, as well as glide cracks opening on low elevation rocky slopes.  

On Saturday, observers reported a large wet natural avalanche that stepped into older layers on a SW aspect at 4500 ft near Red Mountain and several large loose wet avalanches on E-facing aspects in Gold Creek with numerous small Loose Wet natural avalanches on all aspects.

South

NWAC Forecaster Dallas Glass was in the Paradise area of Mt Rainier on Saturday. Dallas found a very hard, frozen crust about 1 foot thick on sunny slopes. He also reported sudden test on the 2/13 facets about 4 feet below the surface.

NWAC professional observer Jeremy Allyn traveled in the Crystal backcountry Thursday. Jeremy found 6 inches of new dry snow moderately bonded to a newly forming crust. He observed limited new loose surface snow concerns on steep sunny slopes. The 2/8 layer was found down 4 feet.