The Bottom Line: The weather and the snowpack will be transitioning Friday. Be patient as the snowpack adjust after this recent period of active weather. Strong winds formed wind slabs in a variety of locations. You will need to look for fresh cornices and snow drifts to identify and avoid wind loaded slopes greater than 35 degrees. If the sun comes out, don’t get surprised by loose wet avalanches coming from steep southerly slopes.
Regional Synopsis
January 10, 2019
We’re about a month into our avalanche forecasting season, and what a wild month it has been. We’ve seen the snowpack grow from near non-existent to over a 100 inches deep at Mt Baker. We’ve seen avalanche warnings blanket our coverage area, had several widespread large natural avalanche cycles, and seen persistent weak layers plague nearly every zone. While the active weather pattern has been a welcomed sight, it’s hard to catch your breath.
It looks like this weekend, and extending into next week, we are entering a calm period in the weather. High pressure over Idaho and Montana will keep Pacific storms at bay for at least the short term. As we enter this period of nice weather, there are a few things on our mind here at the avalanche center.
Old Persistent Weak Layers A high elevation rain event on January 3rd did us a favor in many locations. Besides heavily stressing old weaklayers, the rain created a very strong met-freeze crust, making it extremely difficult to trigger deep avalanches.
There are a few exceptions, and they can be found mainly in the eastern forecast zones. The East-North zone around the Methow Valley and WA Pass did not experience significant rain above 5500 ft, potentially leaving some older weak layers in tact. Areas further east including, but not limited to, Icicle Creek and the Wenatchee Mountains did not receive enough rain to form a strong thick crust. In all of these area, older persistent weak layers are still suspect.
An avalanche on a persistent weak layer in the East-Central zone. Photo: Matt Primomo
Higher Elevations and Remote Trailheads Stormy weather over the last month has been keeping most of us closer to common trailheads and recreating at near and below treeline. With nice weather on tap, some of you may be thinking about heading into higher elevation terrain and exploring around more remote trailheads. If you are heading out, take time to consider a few key pieces of information.
At higher elevations the snowpack is very deep and wintery. This stands in stark contrast to the lack of snow at lower elevations. The snowpack you’ve seen on previous outings this winter, doesn’t represent what you will encounter at higher elevations.
We have not received much information about the above treeline nor remote location snowpacks. That means we have a high degree of uncertainty in these areas.
You will need to make observations as you travel to confirm if the avalanche forecast is applicable the the area where you are traveling. When observations lineup with the information in a forecast, its valid. If you see observations that don’t lineup, it’s time to take a step-back.
If you are heading into our regions highest alpine terrain, remember, NWAC forecast apply to areas below the main Cascade crest, or about 8000 ft. So, if you plan to travel to higher elevations on Mt Baker, Mt Shuksan, Mt Rainier, Mt Hood, or similar areas, you will need the skills and information to evaluate the terrain and snowpack.
If you’re heading into higher elevation terrain, remember we don’t have much information about these snowpacks, and therefore have a higher degree of uncertainty. Photo: SimonTrautman
If you’re heading into higher elevation terrain, remember we don’t have much information about these snowpacks, and therefore have a higher degree of uncertainty. Photo: Simon Trautman
We’d like to thank our NWAC Community for all the wonderful public observation this year. If you are heading out into the mountains, we appreciate you taking the time to let us know what you saw. This is a great way to contribute to the creation of your avalanche forecast. You can submit observations here.
Enjoy the sunshine!
Avalanche Problems
Wind Slabs
Recent winds formed slabs in some unusual locations like well below ridgelines, on the sides of gullies, and in places that are normally scoured. Though you may not see the wind actively loading slopes anymore, the slabs that were built the past few days may take a bit longer than normal to heal. These slabs are resting on lower density snow and sitting over a stout crust, a perfect recipe for avalanches. You will need to use your eyes and sense of touch to locate these dangerous areas as you travel. Feel the snow under you as you travel. Does it feel more firm in one location than another? Does it seem hollow? If you see or feel any of these observations, slabs may be nearby. You can stay safe by traveling on ridges, scoured areas, and any slope less than 35 degrees.
Aspects:
All aspects.
Elevations:
Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 2
Loose Wet
When the sun breaks out, expect loose wet avalanches to become common. Steep slopes that face the sun are the most likely places these will happen. When the surface snow becomes moist, or if you see roller balls or small fan shaped slides that begin to entrain snow, get off of steep slopes. These may pack a punch tomorrow.
