Avalanche Forecast

Weather Synopsis for Friday night through Sunday

Although the Thursday night system didn't have as much moisture as anticipated, Friday night's storm will deliver. A powerful and deepening storm system tracking NE toward the Queen Charlotte Islands will pack a major punch Friday night. Heavy precipitation is arriving on the coastline late Friday afternoon as strong warm front lifts across the region, beginning late in the day. Overnight, moderate to heavy precipitation will slam the Cascades. Mt. Hood will likely be the winner in terms of precipitation with 2-2.5", while Mt. Rainier and Mt. Baker will be in the 1-1.5" range, with most other NWAC stations receiving 0.5-1" of moisture. The warm front will warm temperatures 15F as it crosses the coastline so many areas will see a changeover to rain, particularly during the late evening and overnight hours, before changing back to snow at some point on Saturday. Easterly flow may insulate the passes from the warming during the evening hours, but eventually, but atmosphere will be so warm aloft that Stevens and Snoqualmie may turn to all rain before the wind shift very early Saturday morning. The easterly flow is helping to bring significant water amounts east of the Cascade crest such as in the Mission Ridge and Leavenworth areas.

On Saturday, light to occasionally moderate snow shower activity will gradually diminish during the day, where narrow bands of precipitation may be locally intense. Saturday night, further diminishing snow showers will end after midnight. On Sunday, the front stalled over southern Oregon will lift some light moisture back into northern Oregon and southern Washington as a mild trough digs off the Oregon coast.

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.

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?

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.