Avalanche Forecast

Archived

Mar 18th, 2019–Mar 19th, 2019

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Stevens Pass.

The snowpack is undergoing a major thaw. Large and dangerous natural wet avalanches are possible. This is a good time to step back, and allow the mountains to make the transition.

Discussion

Snow and Avalanche Discussion:

After a prolonged period of snow and below average temperatures, we are experiencing a heat wave with record high temperatures. The snowpack is making a transition from cold and dry, to a spring-like pack. Meltwater is beginning to make its way through the upper snowpack. Along with this, there is a high degree of uncertainty regarding avalanche size over aspects and elevations. The only dry snow left is on direct north facing slopes, elsewhere wet snow is commonplace. Cornices are beginning to sag and break off. The most active period for wet avalanches will likely be late in the afternoon.

From the 13th-18th, observers reported numerous natural wet loose avalanches on the southeast face of Lichtenberg Mtn and southwest aspects near the Skyline area and Windy Mtn. A couple of these avalanches were big enough to bury or kill a person. Significant wet avalanche activity has occurred at low elevations in the neighboring East Central zone with road closures due to avalanches in Tumwater Canyon. There have been several reports of wet slab avalanches on southerly slopes in the past three days. Most notably, a large slide into Tunnel creek likely occurring on the 17th in the afternoon. Also, a handful on Snoqualmie Pass, one at Crystal Mtn, Excelsior Ridge near Mt Baker, and one on lower Mt. St. Helens.

The heat wave is on. Temperature graph from early March through current.

Snowpack Discussion

Coming soon.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.