Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind-stiffened snow overlying a potentially poor bond to the underlying crust has extended the lifespan of large slabs. You can trigger them on steep, unsupported slopes and near rocky areas. Make sure you have the skills to identify and steer around cohesive deposits if you engage with exposed, consequential terrain.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    It is reasonable to engage with avalanche terrain if you know how to identify and steer around areas of wind-stiffened snow. These deposits will be stubborn to trigger 3 days out from the storm, but the setup remains concerning: Lower density snow underlying firm wind deposits has created a difficult to manage slab problem on the upper slopes of Mt Hood. Although the reactivity continues to decrease, the consequences have not. Large slabs triggered in mitigation at Mt Hood Meadows both Monday and Tuesday were reactive to very small amounts of dynamite, suggesting that a rider could easily trigger them as well. Recent reports from the upper mountain identified small facets underlying the slabs above the 2/7 crust. Furthermore, a large widely propagating slab trigged by Mt Hood Meadows Pro Patrol in A-zone involved the 2/7 crust.

    Given the prevalance of wind-affected snow and large wind deposits on the eastern half of the compass, you'll have to be strategic if you wish to engage with avalanche terrain. To steer clear of the problem: identify and navigate between areas of wind rippled or stiffened snow, and avoid steep, poorly supported slopes, and shallow rocky areas. Shallower slabs formed on W aspects are more recent, but moslty too small to harm you.

Avalanche Discussion

Wednesday featured sunshine, seasonably cool temperatures, and light winds throughout the zone. A quiet day of weather gave our wind slabs some additional time to gradually gain strength, but the simi-persistent structure keeps us managing slopes more conservatively due to the potential for slab avalanches up to size 2.5 (very large). We don't have any reports of avalanche activity on Wednesday, confirming that wind slabs are stubborn to trigger at this point. 

Several rounds of snow have accumulated 10" of snow (and 2-3" of water equivalent) above the widespread 2/7 crust. In some areas that storm ended with a bit of rime crust near the surface on Monday evening. The combination of hard slabs and several reports of facets above the 2/7 crust, suggest that slabs may be slower to heal at NWAC upper elevations and above. It is a good time to remember that you're likelihood of triggering an avalanche, the size of that avalanche, and even the problem type can diverge above NWAC forecast elevations. You will need to carefully evaluate upper elevation slopes on Thursday, but plan to make your own assessments if you head above NWAC forecast elevation.

Wet loose activity was limited to a few rollerballs, illustrating that the potential for wet loose activity has largely run its course and is not expected to be an issue on Thursday. Observers reported quality riding in less wind-affected dense powder at middle and upper elevations. 

Following the end of precipitaiton on Monday, areas from Timberline westward experienced moderate wind transport forming shallow, stubborn slabs up to size 1. The wind transport in this terrain was eroding larger slabs formed on more typical aspects on Monday. Areas further east around Mt Hood Meadows experienced less of the ESE winds and it appears that Monday's slabs did not experience the same erosion. As a result, you can expect some variation in the rates that slabs are healing as you move around the mountain. 

Coverage remains unusually thin (or non-existent) on wind-stripped W aspects of ridgelines, while easterly aspects hold thicker snowpacks (along with the potential for large wind slabs). Rocks, creeks, trees, and other shallowly buried objects are still prominent through the terrain and could easily exacerbate the consequences of an avalanche. 

We could really use the observations as snow stacks up. Let us know what you see by submitting an observation here or on the AvyApp. 

Regioni coperte