Mt Hood

The bottom line: Strong east winds near crest line have transported available snow where you might find new wind slabs on lee slopes, mainly above treeline Tuesday. You can avoid triggering avalanches by staying off thickly-pillowed, wind loaded slopes and steering well-around wind-sculpted features on slopes 35 degrees and steeper.

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 Tuesday night through Thursday

Tuesday has quickly transitioned from blue bird high pressure to a mostly cloudy afternoon as high pressure departs to the east and the region begins seeing the effects of the west coast trough. Moisture has spread northward through the day from a trough that extends to southern California. Most of the energy associated with the trough has been spent in California and the PNW will only see occasional light showers in bands rotating northward through Wednesday afternoon.

Freezing levels have lowered substantially by Tuesday with many NWAC sites 10-20 degrees cooler than yesterday at the same time!

Strong easterly winds persist across the Cascades and through the passes keeping sub-freezing air in the lower elevations.

Some light precipitation will spread northward Wednesday but amounts will be very light as the main energy moves inland well south of the area.

A stronger low-pressure system will approach the offshore waters late Wednesday and move NE offshore Thursday. More significant precipitation should rotate across the area Wednesday night with wi little break between bands during the day Thursday.