Bollettino valanghe

Stevens Pass

Feb 13 – 14, 2019Northwest Avalanche Center
Vedi sulla mappa
Archiviato · scaduto 8 years ago

Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
Apri la mappa completa

In sintesi

If you venture in the backcountry be certain of your ability to avoid avalanche terrain. Wind and more snow will stress the snow and make it easy to trigger very large and life-threatening avalanches. Continue to avoid steep slopes and put plenty of space between where you travel and large avalanche paths.

Problemi valanghivi

  • Wind Slabs

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

    Easterly wind will drift snow at upper elevations, forming fresh slabs and further stressing an already tenous snowpack. Avoid any slope over 30 degrees with drifts or where you see the wind blowing snow. Avalanches on wind loaded slopes could be up to 6 feet deep. 

    In sheltered areas you can still trigger large storm slab avalanches in the snow that fell in the past week. The upper layers may slide easily. Today, you can't simply avoid or manage the storm instabilities. Any avalanche triggered in the recent snow could result in a larger and more deadly persistent slab avalanche.

  • Persistent Slabs

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

    Today is not the day to travel in avalanche terrain. If you venture into the backcountry, you must be confident in your ability to put enough distance between you and slopes that could produce life-threatening avalanches. Stay far out from under big avalanche paths and make sure not to get too close to start zones. Persistent slabs can break widely across terrain features, come down on top of you, and can be triggered from a long distance away. These avalanches are difficult to predict and break in ways much wider and in more surprising ways than avalanches that we typically see in the Northwest. 

    The snowpack has seen a rapid and major change. Give the snow some time to adjust. Continue to stick to slopes under 30 degrees and smaller terrain features. Observers have consistently reported; 1) Remotely triggered avalanches. 2) Widespread collapsing of the snow underfoot or a "whumphing" sound. 3) A layer of weak, sugary facets and surface hoar resting on a crust 4-5 feet below the snow surface. Watch for these signs indicating that you can trigger a Persistent Slab avalanche.

Discussion

Snow and Avalanche Discussion

Observers have reported a widespread and prolonged cycle of avalanches involving a variety of aspects and elevations. Common characteristics of these avalanches are very widely propagating crowns about 3 feet deep. Local ski patrols, highway workers, and backcountry travelers all reported extensive avalanching on the night of the 11th, into the 12th, with triggered slides and a few naturals continuing into the 13th. While some avalanches ran in storm layers in the upper snowpack, many appear to be running an old weak faceted layer over 3 feet below the surface. Visibility and dangerous conditions have limited our ability to gather more detailed information. 

Stevens Pass has received over 50 inches of snow since February 8th. More cohesive snow on the 11th and a couple wind events are building slabs along the highway 2 corridor. In addition to avalanches, all the deep snow is building concern for Snow Immersion Suffocation, or tree well hazards. Travel in the mountains with partners and keep them in sight.

A natural avalanche in the neighboring Icicle canyon. Grindstone Mtn, SE, 6,600ft. Photo: Matt Primomo

Snowpack Discussion

Regional Synopsis coming soon.

Regioni coperte