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Avalanche Forecast

Archived

Apr 25th, 2015–Apr 26th, 2015

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

Regions

Stevens Pass.

Don't underestimate the effects of the strong April sun, which can make avalanches touchy Sunday, especially in areas of heavier storm snowfall.

Detailed Forecast

High pressure should begin building into the Pacific Northwest Sunday, causing clearing and slow warming. Temperatures should be cool early Sunday with only a moderate rise in freezing levels by afternoon. This should allow for recent snow over the past few days to settle. 

The main avalanche problems Sunday should shift from any recent storm or wind slab to mainly loose wet avalanches on slopes receiving sunshine and during the afternoon in areas with sufficient snowcover for avalanches. 

Watch for wet surface snow that gets deeper than a few inches, pinwheels or initial small natural avalanches from rocks or cliffs that are signs to shift to lower angle slopes.

Cornices won't be listed as an avalanche problem, but avoid slopes below cornices and areas on the ridge where it may be difficult to know if a cornice is present.

Remember that this forecast applies to elevations up to the Cascade crest and does not apply to higher elevations on the volcanoes where conditions at this time of year are often more dangerous.

The mid and lower snowpack is most areas should consist of stable rounded grains and crust from warm periods this winter. Many areas at low elevations especially in the Olympics and east of the crest do not have enough snow to cause an avalanche danger.

The work of the 3 NWAC forecasters is transitioning to other essential parts of the program before the NWAC closes for the summer.

 

Snowpack Discussion

After a cool, snowy start in early April, mid April provided about a week of warm dry weather. This caused loose wet snow avalanches and consolidation. Layers from early April have stabilized, making any avalanche activity confined to new snow received over the past few days.

A cold front moved across the Northwest on Thursday. The front was followed by a low pressure system, south to southwest winds and a cool unstable air mass that caused snow showers at low freezing levels Friday and Saturday. Storm snow amounts have been highly variable under the showery recent weather pattern. The greatest new snow since Thursday has been at Mt Baker, about 18 inches, and the Mt Rainier, Chinook Pass and Crystal Mountain areas where about 8-14 inches fell. Most other areas along the west slopes have picked up about 2-6 inches of new snow as of Saturday. New snow has already begun to settle Saturday afternoon under daytime warming.

 

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.