Avalanche Forecast

A few big stories stand out in the current snowpack: recent avalanche warnings in the northern zones, persistent slabs in the western areas, and a complex and weak snowpack in the eastern zones.

The northern zone experienced the brunt of this latest weather system. This led to two days of avalanche warnings and at least one large natural avalanche cycle. It's tough to say what the snowpack looks like in areas near and above treeline, but we know those areas received substantial new snow.

Earlier in the week we began forecasting a new persistent slab in our west-slope zones. A layer of buried surface hoar produced avalanches last Saturday, Sunday, and Monday. How did that layer fair after this recent round of weather? In locations like Mt Baker and Paradise, it was well tested with heavy precipitation. In other locations, less water may not have adequately stressed the weak layer. As visibility improves and more observation come-in the picture may become more clear.

In the eastern zones a complicated and weak snowpack exists. Several persistent weaklayers have plagued these regions most of the winter. Don’t expect this to change anytime soon. Snow profiles and snowpack test can give you a glimpse into the persistent layer. Remember, snow profiles cannot prove the absence of a weak layer or that a layer has “healed.”

Following a potent windstorm Saturday night, an upper trough will remain over the area Sunday night and Monday morning. Cells of convection are rotating through the trough offshore and some of these have organized into a band of moderate snow that will cross the Cascades during the evening hours and will affect most areas south of Mt. Baker. Another period of enhancement may cross the Cascades during the early morning hours. Decreasing snow showers will generally end by the end of the day on Monday as a shortwave upper-level ridge cuts off the cool, unstable flow. Fair and clearing skies can be expected Monday night. Pass-level winds will shift easterly after midnight and will become moderate with strong gusts by Tuesday morning

A mature low spins some 600 miles off the N. California on Tuesday, spreading light to moderate snow on a southerly flow. The southerly flow will rapidly erode the cooler air previously in place west of the Cascade Crest, but the cold air should remain in place to the east. Light to moderate precipitation will spread into the area, with the heaviest rain and snow along the coast and in the Olympics.

Snow totals Sunday night through the day on Monday are expected in the 10-14" range for Mt. Hood, 8-12" for Paradise, 5-10" for the Central Cascade passes and 2-6" for Crystal, White Pass, and Mt. Baker.