Avalanche Forecast

A relative break in the weather and lower precipitation amounts will limit the development of avalanche problems Sunday. If you travel in areas closure to the Cascade crest, expect avalanche conditions that more closely resemble adjacent zones to the west. Avalanche hazard will decrease rapidly as you travel east where less precipitation is expected.

If you see blowing snow, drifts, or fresh cornices, avoid nearby slopes greater than 35 degrees. You are most likely to trigger a wind slab on steep slopes below cornices, near convex rollovers, or on unsupported slopes.

At lower elevations, warm temperatures and rain have created wet surface snow conditions. If you see new rollerballs, fresh fan shaped avalanche debris, or experience periods of rain on snow expect to be able to trigger loose wet avalanches on steep slopes nearby. Don’t underestimate the power of even small loose wet avalanches. They may carry you into or over slopes where even small avalanches can have large consequences.

Other springtime hazards are present in the mountains. Cornices have begun to droop. Glide cracks have formed on steep smooth slopes. Creeks are opening at lower elevations. Use caution if you travel near or below any of these hazards.

The amount of new precipitation is largely dependent on locations. Weather stations in the northern and western parts of the zones have reported around 0.75 inches (2cm) of water in the last 24 hours. While weather stations farther east have reported less than 0.1” (<1cm) of water. At higher elevations, this precipitation fell as heavy wet snow. Above freezing temperatures and very light rain were observed up to 5500’. Winds during the storm likely formed new wind slabs on lee slopes near and above treeline.

In the mid and lower snowpack older persistent weak layers can still be found in some locations. You are most likely to find weak older snow on shaded aspects or higher elevations where recent warm temperatures and rain have had minimal effects. You can use snowpack tests to identify buried persistent weak layers, however they are not a decision making tool. We have very limited information on the distribution of and sensitivity of any buried old weak layer. If you have any observations on these layers, please share them with NWAC on our public observations page.

Two common persistent weak layers seen in these zones are:

• 3/25 and 3/22: Buried surface hoar layers found on shaded aspects near and above treeline.
• 2/13 Facets above a firm and thick melt-freeze crust can be found in many locations near and above treeline. This layer is thought to be dormant at this time but may re-awaken with a substantial weather input.

Lower elevations further east of the crest have melted back for the season and no longer present an avalanche risk. 

Observations

On Wednesday, NWAC professional observer Matt Primomo traveled in Hawkins Mountain area. Below 5500 ft about 1 ft of wet surface snow was making Loose Wet avalanches possible on steep slopes. Above about 6000 ft firmer surface snow was limiting the Loose Wet avalanche potential. There were widespread large wet snow avalanches following the weekends storms. The upper two feet of snowpack has undergone a spring transition to melt-freeze grains.

On Monday, a public observation from the Entiat River drainage reported wet snow in the upper 16 inches (40 cm)  of the snowpack on a NE aspect at 6800 ft. Below this, colder drier snow was found with buried surface hoar 2 feet down (60 cm). This layer was reactive in snowpack tests, suggesting propagation was possible. The 2/8 crust was 3 feet (1 m) below the snow surface and breaking down. S through E aspects had a more springlike and consolidated snowpack.