Bollettino valanghe

Mt Hood

Jan 12 – 13, 2019
Vedi sulla mappa
Archiviato · scaduto 8 years ago

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Apri la mappa completa

In sintesi

The bottom line: As the sun comes out and temperatures warm on Saturday, steep, sunny slopes may produce natural loose avalanches at all elevations that could be large. Isolated wind slabs may linger on any aspect at upper elevations and should influence the way you travel for another day or two while they heal.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2
    It has been a few days since the wind has actively loaded the slopes, and the slabs that were built the past few days may be quite thick, but are isolated and becoming more stubborn to initiate.  Mt. Hood Meadows Pro Patrol reported that wind slabs were difficult to find in their terrain on Friday. Wind-drifted snow had been capped by a thin melt-freeze crust, limiting the extent of this problem here. Keep in mind that conditions at Mt. Hood Meadows may be different from your area as variable and shifting winds have been experienced around Mt. Hood in the last week. Approach any steep slopes with caution, and be especially careful of steep, unsupported slopes. Use your eyes and sense of touch to locate areas of wind slab as you travel. Does it feel more firm in one location than another? Does it seem hollow? You can stay safe by traveling on ridges, scoured areas, and low angle slopes.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2
    Sun breaks or strong filtered sunshine will be increasingly likely on Saturday and if you experience them, expect loose wet avalanches from steep, rocky, or sunny slopes. A thin melt-freeze crust observed on Friday will break down quickly when the sun comes out allowing the sun to warm and destabilize the thick layer of dry snow below it. These avalanches may trigger naturally and could be large and dangerous if they entrain significant snow. Don’t let this easier to predict avalanche problem catch you off guard. If you see direct sun on a slope, boot penetration greater than 6” or saturated snow near the surface, Loose Wet avalanches may release. Don’t linger in confining locations like gullies and near creeks, where even small loose avalanche can bury you deeply.

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.

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 Forecast

Weather Synopsis for Saturday night through Monday

A ridge of high pressure anchored over the Intermountain West will lead to a dry weekend. A weak and splitting frontal system offshore has spread some high clouds over the area today. 

There is some nuance to the freezing level forecast with offshore easterly flow continuing to draw colder air and low clouds through the Cascade Passes while much milder air can be found at higher elevations and along the west slopes of the Cascades and Olympics.

The cold pool along the east slopes of the Cascades will slowly erode and moderate through Monday with freezing levels on the rise, but low clouds and cooler temperatures will persist along the lower slopes.

Light to moderate easterly flow through the Cascade Passes and at ridge-crest for places like Crystal Mountain will also persist into Monday despite the overall warming trend.

Regioni coperte