Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Cold temperatures and moderate NW winds will continue to move snow at upper elevations through Wednesday.  It's here that you're likely to trigger a large wind slab avalanche in steep wind-loaded terrain.   

Problemi valanghivi

  • Wind Slabs

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

    Winds will continue to move new and recent snow along ridgelines through Tuesday night and especially on Wednesday as a storm approaches the area.  On Tuesday, observers found widespread wind-stiffened snow when they transitioned into the near treeline elevation band with shooting cracks on a few test slopes.  NW winds on Wednesday may cause unusual loading patterns, so it's important to pay attention and not assume the usual suspects will or won't be wind loaded. 

    Besides observing which slopes are being actively loaded with blowing snow,  look for smooth firm pillows, and textured snow to identify which steep slopes to avoid.   Shooting cracks are a red flag that you can trigger a slab avalanche on similar slopes.  Think about what terrain you're connected to at lower elevations;  large avalanche paths that originate above treeline are likely receiving more wind and loading than you may experience at lower elevations or treed terrain. 

    (2/1/2022)

    A small wind loaded test slope failed and cracked easily.

    Photo: Dallas Glass

  • Storm Slabs

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

    Storm slabs may be less likely to trigger on Wednesday, however think about specific terrain features, like steep unsupported slopes above terrain traps where triggering a storm slab avalanche could have outsized consequences.  Continue to use small slopes and hand-pits to test the new snow, looking for reactive layers in the recent storm snow.   As you travel near and above 4000',  the recent snow overlies a worrisome crust/facet (weak snow) layering that we'll need to track as we continue pile more snow up this week.  

    (2/1/2022)

    A very small skier triggered storm slab avalanche. E aspect. 4400', 4-6" deep, SS-ASc-R1-D1-S

    Photo: Dallas Glass

Avalanche Discussion

It was easy to find reactive storm layers 12-15" down with quick hand tests in the Alpental Valley Tuesday.  While the recent snow was largely right-side up and bonding well to the old snow surface,  NWAC forecasters were able to trigger a small storm slab on a test slope.  Alpental Patrol also reported shallow storm slabs during avalanche mitigation, of the 6-8" variety on Tuesday. 

The recent snow helped improve travel conditions after a rough few weeks with a settling 8-10" near Pass level increasing to 15-20" as you climbed into the near treeline band Tuesday.  This new snow overlies a variety of old snow surfaces, including near surface facets and facet/crusts combinations (1/30 interface) depending on aspect and elevation.   Freezing rain below 4000' Sunday helped destroy some of the weaker grain types, so we have less concern at the lowest elevations moving forward.  With incremental storms loading and testing the 1/30 interface this week, we may find ourselves in a touchier situation in a few days. 

The lower/mid snowpack is strong. We are not tracking any weak layers or interfaces of concern with all eyes on the upper snowpack moving forward. 

Regioni coperte