Avalanche forecast

Avalanche forecast

Payette Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A persistent weak layer of buried surface hoar looms 2-3 feet beneath the snow surface. A persistent slab avalanche, although becoming less likely, would be large and destructive. Freshly built wind slabs may become reactive today with recent snow and W/SW winds.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    A persistent weak layer of buried surface hoar was responsible for several natural and human-triggered avalanches within the past week (see photo to right). This weak layer is buried anywhere from 60-90 cm (2-3 feet) beneath the snow surface. Most of these natural avalanches ran during or right after this week's heavy, wet storms. We are most concerned with this persistent weak layer at middle and upper elevations, particularly on NW, N, NE, E, and SE aspects. You are most likely to encounter this weak layer at a trigger spot in steep terrain (think thinner areas of snow around rocks or cliffs). Human-triggered avalanches, while becoming less likely, would be large and destructive. The best tool for these uncertain scenarios is avoidance of steep, avalanche-prone terrain.

    (12/29/2022)

    Natural avalanche observed on Thursday (12/29) north of Slab Butte on a NE aspect. This likely ran sometime on Wednesday. Shout out to some local snowmobilers for this great observation.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    10-20 cm (4-8") of snow has fallen within the past 24 hours throughout our advisory area. Winds were calm yesterday and visibility was difficult at best. The density of this new snow was right around 10-12%. In some locations, especially around West Mountain, winds were blowing 10-25 MPH last night out of the W/SW. Today, you may encounter freshly built wind slabs, particularly on N, NE, and E aspects at middle and upper elevations. These wind slabs could be anywhere from 30-45 cm (12-18") deep. Pay attention to clues like shooting cracks, stiff or hollow feeling underneath skis or sleds. These are indicators of dense snow over softer snow and could produce wind slab avalanches in steep terrain. 

    (12/21/2022)

    Observation submitted of a small wind slab avalanche north of Tamarack Resort about 7500' on an east aspect, about 100 wide, depth range 6" to 2'

Avalanche Discussion

Today's avalanche forecast is sponsored by Mile High Powersports of McCall. Thank you for supporting the Payette Avalanche Center.

What a wild week it's been. We saw a series of warm, moist storms slam into our region and drop 30-60 cm (1-2 feet) of snow, rain up to 7500', and strong SW winds. We issued an Avalanche Warning on Tuesday with HIGH danger. The persistent weak layer of buried surface hoar became overloaded in certain areas and was responsible for several natural and human-triggered avalanches. Although the colors on the danger scale are much different than earlier this week, two of the avalanche problems remain the same. The destructive size of a persistent slab avalanche has not changed. What has changed is the likelihood of triggering. Natural avalanches on this persistent weak layer are unlikely. However, human-triggered avalanches, although unlikely, still remain a possibilty in certain terrain. If you want to avoid exposure to avalanches today, terrain selection is key. Avoidance of steep, avalanche-prone slopes above 7000' is the only sure way to avoid triggering a persistent slab avalanche.

The snowpack below 7000' became heavily saturated during Monday/Tuesday's rain event. With several cold days and nights since, the snowpack at lower elevations is strengthening and becoming fairly uniform.