Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

The storm will have moved on by Saturday morning, but large quantities of snow remain. Stick to conservative, lower-angled terrain if you find more than a foot of new snow. Sunbreaks could set the stage for loose snow avalanches initiating from cliffs and other steep terrain features.

Problemi valanghivi

  • Wind Slabs

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

    Large quantities of snow fell in the Southern Cascades over the past 48 hours, with the East South forecast zone seeing more precipitation and snowfall than from the typical storm. It’s not guaranteed that the new snow will stay unstable enough for widespread natural or human-triggered avalanches on Saturday, but the quantities of new snow are too much to ignore.

    The biggest issue on Saturday will likely be an increase in wind speeds that starts drifting snow and forms fresh slabs. Drifting snow will be the main sign of active transport. Monitor snow depth and stiffness as you gain elevation and change aspects. You are much more likely to trigger an avalanche on slopes with recent wind loading. With this much snow to blow around, avalanches could end up being larger than you might expect.

    Fresh slab layers are still a concern in wind-sheltered terrain. The best policy is to give the new snow a day or two to settle before venturing into aggressive terrain.

    (3/13/2024)

    Visual  clues help highlight where wind slabs may occur.

    Photo: Dallas Glass

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Temperatures are forecast to stay cool, but the March sun is strong enough provide plenty of warmth and get loose snow moving on steep, sunny slopes. Loose snow avalanches usually initiate in steep and rocky terrain or treed areas. You can also get the snow moving yourself if traveling across or down steep slopes. Look for the initial signs of warming like rollerballs and very small loose snow avalanches. Keep track of what’s going on overhead as the day warms.

    (1/27/2023)

    An example of rollers and small loose wet on a slope seeing direct sun.

    Photo: Julz Holder

Avalanche Discussion

The southern Cascades have seen much-needed snowfall from the latest storm. The Bumping Ridge SNOTEL picked up over two feet of new snow and three inches of precipitation over the last few days, adding significantly to the snow cover. Green Lake had roughly 2 inches of precipitation in the same time period. Unfortunately, temperatures also moved upward on Friday with a high of 35°F at Green Lake. Expect to find some rain- or warming-affected snow at low and mid elevations. As usual, more snow can be found as you move west toward the Cascade Crest.

Persistent weak layers that were active in the Cascades in late February and early March are gaining strength and considered to be less active, but this latest load of new snow will put that hypothesis to the test . We've been tracking the 2/13 buried surface hoar and facets around the 2/7 crust. An NWAC forecaster traveled to the Pinegrass Ridge area last week and identified these layers about 2 feet below the surface. On west aspects, they produced propagating test results, while on southerly aspects, the layers were gaining strength. The last (and only) known persistent slab avalanches that failed in the East South occurred on February 28th around Darland Mountain. In the nearby East Central zone, snow professionals have reported no notable snowpack test results associated with these layers for the last 3 days. 

NWAC Forecasters produce more accurate avalanche forecasts when the community chips in. Please let us know what you're seeing out there.

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