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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

Snoqualmie Pass.

The snowpack in the Snoqualmie Pass area is struggling to adjust to these warm temperatures. Be patient and let the mountains make this transition. Stay away from steep open slopes and a don’t linger in locations where avalanches can run and stop.

Discussion

Snow and Avalanche Discussion

This week’s warm weather is a tough transition for the mountain snowpack. We spent nearly six weeks with below average temperatures. Now, on Monday, temperatures in the lowlands are hitting record highs. That’s a big change. When it comes to the snowpack, big changes often mean big problems. On Tuesday we’ll be heading into our 3rd straight day of above freezing temperatures at Snoqualmie Pass. While a cool easterly wind may delay thawing of the snow surface, it won’t take much time for the sun and warm temperatures to create wet snow.

On Monday morning, NWAC staff observed several avalanches that occurred over the weekend. The presence of numerous overlapping debris pile should be all the reminder you need, that this avalanche cycle is ongoing. Of note were a few isolated wet slab avalanches these were all relatively small and were triggered by loose wet avalanches from above.

During spring periods like this, plan for changing conditions. Slopes you travel on in the morning can be very different by mid-day. On Monday, slopes went from frozen to wet in the matter of 30 minutes on sun-exposed slopes. Be leery of traveling near or under cornices. They are experiencing the stress of this heat too, and may fail without warning.

Snowpack Discussion

New Regional Synopsis 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.