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RegisterJan 18th, 2017–Jan 19th, 2017
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The snowpack in the Olympics and Cascades is undergoing a lot of change and there is less than the usual certainty in which avalanche problems and danger levels to indicate. It might be a good plan to wait until Friday when conditions are better known and should be more stable.
Winds and snow showers will decrease Wednesday night and Thursday with cooler temperatures.
Heavier storm snow should be seen above 5000 feet in the north such as at Mt Baker and above 6000 feet in the south such as at Mt Rainier by Thursday with lighter storm snow in the Cascade Passes.
The greatest likelihood of new wind slab should be at higher elevations on the volcanoes where storm snowfall is heaviest. But bed surfaces such as underlying freezing rain crusts may make wind slab sensitive in the Cascade passes.
New storm slab will be most likely in any areas that experience rapidly accumulating snow of more than an inch an hour for several hours. Bed surfaces such as underlying freezing rain crusts may make storm slab sensitive as well in the Cascade passes.
Wet slab or glide avalanches seem possible for another day in the below treeline on Thursday while water from the atmospheric river drains from the snowpack. Wet slab avalanches will be indicated as an avalanche problem in the below treeline since most reports on Wednesday indicated wet slab avalanches. Avoid areas below unsupported steep terrain without trees especially if the slope is known to have a smooth ground surface.
The snowpack in the Olympics and Cascades is undergoing a lot of change and there is less than the usual certainty in which avalanche problems and danger levels to indicate. It might be a good plan to wait until Friday when conditions are better known and should be more stable.
Weather and Snowpack
An Arctic air mass was over the Northwest with fair, cold weather last week. Surface hoar and near surface faceted crystals probably formed in most areas during that period.
A drastic change was seen when an atmospheric river moved to the Northwest Tuesday and Wednesday. This caused heavy rain up to about 5000 feet in the north and up to about 6000 feet in the south with snow at higher elevations. Sleet or freezing rain Tuesday has been followed by a change to snow at higher elevations at Stevens and Snoqualmie on Wednesday. An avalanche cycle is expected to have occurred in some or many areas.
Observations the next couple days should help determine to what extent any of the surface hoar and near surface faceted crystals from the fair cold weather might have survived the atmospheric river event.
Recent Observations
NWAC pro-observer Dallas Glass was at Stevens Pass on Tuesday and reported that the sleet and freezing rain had already formed a 1/4 inch crust over the snowpack by midday.
The Mt Baker pro-patrol and NWAC pro-observer Simon Trautman reported wet slab and glide avalanches from the Mt Baker area on Wednesday. A natural glide avalanche was seen on a NW slope at 3800 feet with a 1-2 foot x 100 foot crown. Explosive control gave a very large wet slab with a 3 foot x 1000 foot crown above the road to the ski area on a NNW slope at about 4000 feet. Another wet slab was seen on a west slope at about 4000 feet. Lastly a wet slab ran starting at about 5000 feet ran on a S slope on Church Mtn to near Highway 542.
The Stevens pro-patrol on Wednesday morning reported only small wind slabs along the ridge tops and small triggered loose dry avalanches. New snow was not bonding well to the freezing rain crust.