Mt Hood

The bottom line: Loose wet avalanches are most likely on steep, rocky and sunny slopes. Avoid lingering in terrain traps where even a small loose wet avalanche could cause injury. You may also find lingering wind slabs on steep unsupported slopes at higher elevations.

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.

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

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!

Weather Synopsis for Sunday night through Tuesday

Strong high pressure will remain anchored over the Inland NW, blocking weather systems from reaching the area through at least Tuesday.

High freezing levels and mostly clear skies will continue through Monday afternoon with a few important caveats. Constant light to moderate easterly flow will cause locally cooler temperatures in and around the Cascade Passes. Temperature inversions like the one seen this afternoon at Washington Pass stations with temperatures near 40 degrees at ridgetop (6700 ft) and a chilly 25 degrees at Pass level (5400 ft) will be common. Temperatures for areas further west of the Cascade crest like Paradise, Mt. Baker and Hurricane Ridge will continue in the 40s to even 50s through Monday. Areas of low clouds should be confined to the lower slopes on the east side of the Cascades. 

The ridge will begin to shift east and be undercut by an open trough entering central California Monday night and Tuesday. This should allow for freezing levels to first begin lowering in the south Washington Cascades and Mt. Hood area late Monday afternoon. High clouds will spread northward Monday night, with a mix of high and mid clouds and steadily decreasing freezing levels for all areas on Tuesday.