Avalanche Forecast

Over the last several days a variety of snow surfaces have developed in the Snoqualmie Pass area. Firm crusts, sugary facets, small surface hoar, and rimed surfaces have all been reported from this area. You can pay attention to the surface as new snow falls. Was the snow surface weak? How is the new snow bonding to the old snow? We will want to watch this new interface as the snow begins piles up.

Reports this week from Snoqualmie Pass indicated difficult travel conditions in many areas. You may encounter breakable crust, very firm surfaces, and/or open creeks as you travel.

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.

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 the 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.

A strong closed low slowly weakening and filling off the California coast is beginning to veer northward while it sends a chunk of energy directly into California. Wednesday night, a weakening band of moisture will lift northward and spread moderate snowfall to Mt. Hood and the east slopes of the southern WA Cascades with lighter snowfall for other areas.

On Thursday, expect increasing S then SW flow as the low tracks about 250 miles off our coastline, with continued cool easterly flow through the passes. Periods of light snow are expected with higher snow levels west of the Cascade crest. The main energy with the low will arrive from the SW late Thursday, bringing moderate rain and snow throughout the region into Thursday night. A wind shift late Thursday night is likely to change Snoqualmie pass to rain, but slightly higher elevations will remain snow. 

On Friday, rain and snow showers will decrease as the initial low departs, but a second low tracking to our NW, well offshore, will spread increasing moisture to our coastal regions late in the day as snow levels rise.