Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Apr 8th, 2018–Apr 9th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

The avalanche danger will rise Monday as sunshine and warm temperatures will quickly make recent snow unstable. You can encounter a variety of avalanche dangers, including Wind Slabs, Loose Wet avalanches, Cornices and Glide avalanches. Use visual clues such as fresh cornices, wind drifted pillows and cracks in the snow all indicating that you could trigger a Wind Slab avalanche. Give fresh Cornices a wide margin of safety and limit exposure on steep sun exposed slopes or where the surface snow is becoming wet.  

Detailed Forecast

Rapid clearing and warming is expected Monday. This should create dangerous avalanche conditions following the weekend's strong winter-like storm cycle. 

Fresh wind slabs will be easy to trigger on steep lee slopes below ridges and features where wind drifted snow exists.

Recent storm snow will become wet, making Loose Wet avalanches likely, especially on steep sun exposed slopes during the late morning and afternoon. Watch for signs of wet snow conditions such as sluffing, roller-balling and any natural Loose Wet avalanches.

Fresh large cornices will become fragile with the sun and warming. Give cornices a large margin of safety and avoid travel on slopes below, as cornice failures may trigger large avalanches on slopes below.

Snowpack Discussion

A strong storm over the weekend caused rain Saturday to high elevations followed by cooling and new storm snow of a foot or more by Sunday afternoon. The new snow was transported by periods strong winds that built fresh Wind Slabs on a variety of aspects, especially below ridges.

The recent storm grew fresh cornices along exposed ridges. 

Older weak snow has been observed on N-E aspects near and above treeline above a crust over the last 2 weeks. This layer is generally 1 to 1.5 feet (30-45 cm) below the snow surface. Rainfall and continued above freezing temperatures Friday night and Saturday may allow Wet Slabs to fail at this interface.

There are no other significant layers of concern in the snowpack at this time.

Observations

Park rangers reported about 1 ft of new snow as of Sunday morning.

On Friday 4/6, NWAC professional observer Matt Schonwald found the facets above a crust on NE aspects between 5200-5400 ft healing.  While this interface may come into play with Wet Slabs Saturday, the Persistent Slab problem has ended. Matt also found glide cracks opening on the 20th of June path. Weak snow at the ground could allow the 85 cm of firmer snow above to fail as a Glide avalanche if thoroughly wetted. While he found other areas with glide cracks, they were not widespread. The snowpack on solar aspects is becoming patchy, especially below treeline. 

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.