Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow is slowly accumulating, and you could trigger freshly formed slabs at higher elevations. Check for instabilities at the new snow, old snow interface and in any area exposed to wind drifting. Increasing ridgetop winds may create dangerous conditions towards the end of the day.

Problemi valanghivi

  • Wind Slabs

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

    As new snow adds up, winds are lightly drifting it into more cohesive slabs at higher elevations. You could trigger slabs in areas with heavier drifting, and they could propagate a surprising distance on weak old interfaces. For the most part, these are likely to be fairly shallow. Increasing westerly winds the second half of the day should ratchet up the danger, and some alpine areas may become dangerous later in the day.  

    Look for clues to how wind-drifted snow may react before entering larger features. You can check to see what may happen with hand pits, skin track tests, and small test slopes. Look for shooting cracks and small slabs as indicators that you could trigger an avalanche. Aside from slabs, small loose wet avalanches could become possible at low elevations if temperatures warm up later in the day.

    (12/30/2022)

    Example of long shooting cracks in a fresh wind slab. These long cracks are bullseye information of unstable snow.

    Photo: Rob Pollard

Avalanche Discussion

Light to moderate amounts of snow fell throughout the zone on Saturday, and that should continue through the weekend. The next wave should favor the east slopes with southeastery flow. Once the winds switch back to westerly in the mid afternoon on Sunday, they should increase- That's when we could begin to see the avalanche danger increase notably at higher elevations. The new snow is covering up a wide range of conditions including small near surface facets on sheltered and northerly slopes, slick sun crusts on slopes that receive direct sun, and various degrees of stiff wind packed snow. Some areas held isolated patches of recently buried surface hoar on shaded slopes. Lower elevations generally held firm and icy crusts. 

Katie was in the upper White River drainage on Saturday, and found 4-8" of new snow over older surfaces. Wind slabs were small and stubborn, but she was able to get some fracturing nonetheless. Tilt tests highlighted a weakness at the new/old interface.

The last significant storm (and resulting avalanche cycle) in the East Central was over MLK weekend. This formed a melt-freeze crust in the snowpack, which acts as a landmark in the upper snowpack. You can find this crust 6-18" below the surface in may areas. The cold weather weakened the snow above and below it into near crust facets. As new snow begins to add up, this creates a weak structure that we'll have to watch closely. 

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