Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

A quick-hitting storm should peak overnight on Saturday, leaving behind dangerous avalanche conditions for you to manage on Sunday. Look for the depth and reactivity of wind-drifted piles of snow to increase as you ascend in elevation or on the volcanoes where more snow is expected. You should avoid any slope over 35 degrees if you notice signs of unstable snow or suspect it to be wind-loaded.

Problemi valanghivi

  • Wind Slabs

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

    Although you may be able to trigger an avalanche on any steep slope over 35 degrees on Sunday, we’re most concerned about wind-loaded areas where thicker and possibly more reactive slabs could exist. You can look for textured surfaces, fresh drifts behind objects, or smooth pillow-like piles of snow to help you identify wind-loaded slopes. Larger slabs could be hanging below freshly built cornices near ridgelines or on convex features. Using small test slopes as you travel can help you get an idea of how the new snow is reacting to your weight, and small hand pits can give you an indication of how well it has bonded to the existing surface. If you have any doubt, default to slopes less than 35 degrees.

    (1/20/2023)

    A recent Wind Slab avalanche that was observed on Mt. Adams on 1/20. Note its location below a ridgeline and originating at the base of rocks.

    Photo: Paris Gore

Avalanche Discussion

The storm rolled into the West South a little later than anticipated on Saturday, but when it did, it showed up in force. Temperatures quickly dropped as wind and snow began to impact the zone, with NWAC’s weather station at Camp Muir recording several hours in a row of gusts over 100 mph. Closer to the crest, stations at White Pass and Crystal Mountain were recording gusts into the 50s and 60s. The storm is expected to continue during the overnight hours and into the morning on Sunday with higher snow accumulations expected on the volcanoes. This is helping to drive the hazard rating around the zone. There’s a chance you could find some smaller slabs and potentially locally lower hazard in areas that receive less snow. Regardless of your location, you could find that the most dangerous avalanche conditions are in the morning as the snowpack adjusts to the recent load.

The new snow has been falling on a variety of surfaces and further increasing the depth over the prominent MLK crust. On sun-exposed slopes, a sun crust formed on Friday, while shadier slopes contained some weaker surfaces. We do not have any information from Saturday indicating whether these weak surfaces survived the onset of the storm. If they did, you could see isolated avalanches breaking in some surprising ways such as spanning far distances or wrapping around terrain features. Make sure you take a minute to check the bonding of the new snow to the old surface to see if it is failing easily wherever you’re recreating.  On slopes that contained the sun crust, a bed surface may now exist for avalanches to run far and fast, whether that’s in loose form or as a slab. Any avalanche should be confined to the snow above the MLK crust (about 1.5-2 feet below the surface) and the majority should revolve around the new storm snow.

Regioni coperte