Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

A persistent weak layer of decomposing surface hoar and near-surface facets is becoming stubborn, but still has the potential to create large avalanches. The weight of a snowmachine will be more likely to impact this buried weak layer than the weight of a person. 3-5 inches of snowfall overnight with south and west winds will create shallow wind slabs at elevations above 7000 feet.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2

    A persistent weak layer (PWL) of decomposing surface hoar and near-surface facets lies 45-55 cm (18-24") beneath the snow surface. This PWL was responsible for several human-triggered avalanches since last Tuesday (01/10). You are most likely to find this PWL on aspects that face the northern half of the compass and at elevations above 7000'. In the southern portion of our advisory area (West Mountain), the buried surface hoar was much more preserved and therefore very sensitive. Snowmobile-triggered avalanches were reported as recently as Sunday (01/15) (Public Observation here). In the northern part of our advisory area, the surface hoar is decomposing and small-grained facets are more of the culprit in these areas.

    This is the third PWL that has been buried this season. Each one has created avalanches and then slowly becomes stubborn (more difficult to trigger). Snowmobilers and snowbikers will be more likely to trigger these avalanches than skiers and snowboarders. As these persistent slab avalanches become more difficult to trigger, folks should still be thinking about the impacts of a large (D2) avalanche. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    3-5 inches of snowfall overnight coupled with southernly and westerly winds will likely create sensitive, albeit shallow wind slabs today. You're most likely to encounter wind-deposited snow at elevations above 7000'. Winds were all over the place last night so north and east-facing slopes will be most suspect this morning. Winds are predicted to shift out of the north today. South-facing slopes could see wind-deposited snow forming shallow slabs later this afternoon.

    Although shallow, wind slab avalanches could create problems for two reasons:

    1. The areas you're most likely to encounter wind slabs this morning are the same areas you could encounter a persistent slab avalanche (see problem above). Two avalanche problems are more difficult to manage than one (or none).
    2. Small avalanches have the ability to knock us off our feet and send us into consequential terrain we didn't intend to enter. 

    (1/18/2023)

    Shallow cracking in wind-affected areas

    Photo: Studley

Avalanche Discussion

Today's avalanche forecast is sponsored by Brundage Mountain Resort. Thanks for supporting the Payette Avalanche Center.

The song remains the same today. Two avalanche problems we should all be familiar with by now: persistent slab and wind slab. We have been graced (or plagued) with these two problems for the majority of the season thus far. Since the post-Christmas rain event, we've seen consistent, light snowfall interspersed with a few dry periods here and there. Those dry periods created weak layers on the snow surface, which were subsequently buried. Our current persistent slab problem peaked at the end of last week and we have not had reports of human-triggered avalanches on this PWL since Sunday (01/15). As the name implies, persistent weak layers "persist" longer than we want and sometimes expect. Although folks may be getting tired of hearing the same tune, it's not time to let your guard down. Your travel plans in the mountains should involve a discussion with your partners about each of these avalanche problems today and how to avoid them.

As snow continues to accumulate at lower elevations with colder temperatures, we could expect to see dry loose snow (or sluffs) moving at middle and lower elevations today (particularly in steep terrain).