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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Generally, stable snow conditions exist. 3-5" of snowfall along with S/SE winds today will be just enough to increase the avalanche danger throughout the day. Watch for instabilities within the new snow, such as slabs of wind-deposited snow and dry loose snow (sluff). New snow will not bond well to previous surfaces such as melt-freeze crusts.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    3-5" of snowfall throughout the day will provide just enough new snow for S/SE winds to transport into sensitive slabs. You can expect to find slabs of wind-deposited snow 6-10" thick building later in the day. You're most likely to encounter wind slabs on north-facing terrain above 7000', especially below ridgelines. Local terrain features can influence prevailing wind direction and wind slabs may be found on multiple aspects above 7000'. Watch for increasing signs of instability like shooting cracks within the new snow. Look for clues of wind-deposited snow like drifts, pillows, or fresh cornices. As new snow accumulates throughout the day, think about dialing back your terrain choices to steer clear of places where wind slabs are building.

    ADDITIONAL DISCUSSION: The other variety of new snow that may pose a problem today will be dry loose snow (sluff). Whether it be dry loose or wind slabs, this new snow will not bond well to previous snow surfaces such as melt-freeze crusts. You're most likely to find melt-freeze crusts on solar aspects. However, some east and west-facing aspects will be holding a thin crust as well. Anywhere there's a crust, expect new snow to move easily on these slick surfaces.  

Avalanche Discussion

Today's avalanche forecast is sponsored by Franklin Building Supply of McCall. Thanks for supporting the Payette Avalanche Center.

Yet another avalanche forecast that hinges upon the weather forecast. Yesterday, we found generally stable snowpack conditions in the northeast portion of the forecast area. For well over a week now, we've been concerned primarily with new snow problems (dry loose, wet loose, storm slab, or wind slab). Throughout the last several weeks, we've seen only three periods of dry weather. Each time, solar aspects become moist and develop a melt-freeze crust and surface hoar and/or near-surface facets form on the snow surface. Weak snow has been forming adjacent to buried melt-freeze crusts on solar aspects. There has not been enough snow on south-facing slopes to "slab up" and become an avalanche problem. There are certainly pockets of buried weak layers within the upper 1-2 feet of the snowpack. As of yet, we've not witnessed these persistent weak layers posing a significant avalanche problem. Pay attention to changing snow conditions throughout the day and continue to dig into the snow to look for signs of instability.

Spatial Variability

Yesterday, the PAC toured from 6600' up to about 7700'. We dug one pit on a NE-facing slope around 7000'. Here we found a generally stable (or right-side up) snowpack with no signs of propagation potential or buried weak layers. Skiing an E-facing aspect, we observed the upper 1-2 inches of snow becoming moist around mid-day (loose snow beginning to "set up"). We noted this to be a problem on solar aspects harboring a melt-freeze crust where wet snow would move easily on steeper terrain. In the afternoon, we skied a northwest slope and found softer snow with minimal dry loose snow moving (sluffing) on terrain steeper than 35 degrees.

We dug a second pit on the NW aspect around 7500'. This location was steep (35 degrees) and shallow (150-175 cm). This particular terrain feature was harboring a thick layer of facets about 100 cm down. An ECT propagated at 13 taps through the entire column. This poor structure alone was concerning. We know that these particular areas are an anomaly and are not entirely representative of the snowpack throughout the region. But, they do exist and it's worth noting. Terrain features such as this (steep, shallow/rocky areas) can prove to be excellent locations to trigger an avalanche. You can minimize exposure to these spots by eyeing a slope carefully before jumping on it and discussing with your travel partners where you think these shallow spots might be hiding.