Bollettino valanghe

Olympics

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind slabs will be large at upper elevations and you can trigger them on a steep or poorly supported slope. At middle elevations, steer around smaller lens-shaped where drifts thicker than 6" pile up above a firm crust. Make sure you have the ability to arrest a fall if you encounter exposed ice in wind-stripped terrain.

Problemi valanghivi

  • Wind Slabs

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

    At upper elevations, you are likely to find that winds formed large drifts within a layer of upside down snow that fell Wednesday night. You may not find the 3/11 rain crust at these elevations, so at these elevations, you might find an average of 1.5 ft of snow above the crust. Slabs could be 3 ft or deeper in more heavily loaded locations and further down on the slope than you expect, creating avalanches that would be difficult to escape. Less wind affected new snow may obscure these slabs.  At upper elevations, avoid wind loaded aspects steeper than 35 degrees.

    The situation becomes far easier to manage at middle elevations where you are likely to easily identify the recent snow depth above the 3/11 crust. In the Hurricane Ridge area, you can expect 4-8" of lower density snow above a firm crust. In areas where this snow drifts more deeply and becomes cohesive, you could trigger an avalanche up to size 1.5. Steer around areas below freshly formed sharp wind drifts or where you encounter stiffer, punchy layers - even if they are not on the snow surface.

    Example: These are the types of avalanches you might trigger at middle elevations. They will be larger, more widely propagating, and further down on the slope at upper elevations.

    Photo: Sam Luthy ONP

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Dry snow falling since Thursday is low density and may continue to bond poorly to an underlying crust or old snow interface. With cold temperatures in continuing in the forecast, you could destabilize this snow on slopes approaching 40 degrees. Evaluate small test slopes before engaging with committing terrain where snow running with you could knock you off your feet at an inopportune moment. Terrain traps can amplify the impact of this loose snow where snow accumulates in a depression or fold on a slope.

    Example: Dry loose running above a rain crust.

    Photo: Payton Schiff

Avalanche Discussion

ONP Rangers dug around on a N aspect at 5230 ft just below Victoria Overlook on Thursday. They found 2-3" of low-density snow above a variably breakable 1/4" knife-hard 3/11 crust with 4" of wet, junky snow below it. Snowpack tests relealed the potential for wet slabs around 5.5" thick, releasing easily on column isolation and propagating across an extended column in snowpack tests. We think that continued cold temperatures should make the 3/11 crust thicken and become a "new ground" in the terrain, but if conditions don't align with that forecast, dial back your terrain selection.

We're expecting about 3-6" of new snow over the next 24 hours, mostly falling Thursday night, adding to an estimated 4" of snow that fell on Thursday. Middle elevations should have 5-10" of snow above the 3/11 crust. Just like higher elevations, which may not have seen rain since 3/8 and therefore have much thicker snow depths above the most recent crust, the southern Olympics will receive more moisture and may develop a storm slab. If you find more than 8" of snow above the crust, assess the bond with the underlying crust and the cohesion of the overlying slab. Small test slopes can help you make this assessment before you engage with consequential terrain.

On the windward sides of ridges, the crust may be exposed and shiny. Be prepared with sharps and know how to use them to arrest a fall if you choose to travel on dangerously slick steep slopes.

Most slopes above 3800 ft now have some snow on the ground, but you don't get continuous coverage greater than 6" deep until you reach around 4500 ft.  Even above that elevation, coverage remains poor in the trees, on windward aspects, and near ridges. Travel cautiously as rocks or barely submerged obstacles may exist just beneath the snow furface.

Regioni coperte