The Bottom Line: The avalanche danger has significantly decreased following Friday night's heavy rain event. Expect the previously wet surface snow to refreeze with cooler temperatures forecast.Fresh wind slabs that formed on steep unsupported slopes at higher elevations may extend down into the near treeline band.
Snow and Avalanche Discussion
Friday's night storm was wet and windy but sadly did not leave much snow in its wake. Generally light snow should refresh the Mt. Hood area Saturday night and Sunday morning. New snow and winds are not expected to significantly impact the avalanche danger Sunday. That means you should be looking for recently formed wind slabs on steep unsupported slopes at higher elevations, using visual clues such as snow drifts and blowing snow, which can help you locate where avalanches may be more likely.
Regional Synopsis
January 16, 2019
Since Friday, January 11, we’ve enjoyed a spell of generally nice weather in the mountains. This allowed for some great views, enjoyable outings, and lots of snow observations. A more active weather pattern beginning Thursday, January 17th will bring this nice weather to a close.
During this time period, the snow surfaces around the area have changed dramatically. This forms the foundation for a few current trends we are seeing in the mountains.
New Snow Problems
Reports from around the area indicate a wide variety of snow surface conditions prior to new snow on January 17th. We’ve heard about breakable crust, very icy surfaces, sugar facets, surface hoar, and rime. What snow surface you encounter can depend on aspect, elevations, and general location.
As a series of winter storms impact the area, how will the new snow bond to the old snow surface? This can be tricky to predict. As the snow starts to pile up, make lots of shallow snow observations. Shovel tilt test, hand shears, and small slope test can all help you track how the new snow is bonding to the old snow at different aspects and elevations. Stop and take a look at where the snow is failing. Do you see large grains of snow? Do they look like feathers? Do they act like sugar? How far below the current snow surface are they?
Old Snow Problems
There are still lingering persistent weak layers in the eastern zones of the cascades. You are most likely to find weak older snow in areas further east from the Cascade crest where snowpacks are shallower, more variable, and generally weaker. In some locations, weak snow near the ground can still be found. These basal facets have hung around all season. The only way to gain information about these old persistent weak layers is to get out your shovel and dig. Because of the size of our forecast zones and the variability in the snowpack, it's important to make snow observations as you travel. We’ll keep watching these old layers, but let us know what you see while you are in the mountains.
Avalanche Problems
Wind Slabs
Look for recently formed winds slabs above treeline and potentially near treeline Sunday. Approach steep unsupported slopes with wind-drifted snow cautiously, feeling for firm or hollow sounding snow as a sign that wind slabs may be present. If more than 6 inches of snow accumulates on Sunday, use caution on convex rollovers and open slopes steeper than 35 degrees even in wind sheltered terrain.
