Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Stay atuned to what the winds are doing, and look for older wind affected snow as you travel. Wind slabs could still be reactive and large enough to hurt you at upper elevations. Steer around consequential or unsupported steep slopes if they appear drifted or textured. 

Problemi valanghivi

  • Wind Slabs

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

    You could travel on many slopes and not trigger avalanches, but you could still find some areas where triggering a large wind slab is possible. In the alpine, slopes are more exposed to wind drifting and are more likely to be affected by winds. The snow is beginning to settle, but it settles slower at higher elevations. Small wind slabs could also form during the day with southeasterly winds at ridgetop.

    Pay attention to how the snow changes as you travel. Look for textured surfaces, and active transport, and cornice formations. Look for cracking with wind stiffened snow. Very steep, convex, and/or unsupported slopes near rock features may be most likely place to trigger a slab. Steer around areas that you think could hold this problem. Stay back from cornices as they may be growing and could break off.

    (12/9/2022)

    Wind loaded slopes will often exist directly under freshly formed cornices like this. 

    Photo: Mitchell Barton

Avalanche Discussion

Sunday was a beautiful day to start the year 2023. Sun was out above some low valley fog, and steep south facing slopes likely formed a sun crust. Observers reported firm travel on the ice crust at low elevations, and soft, weakening surfaces on the crust higher up.  Ridgelines showed drifting from both east and westerly winds, and Andy found a double cornced ridge near Sasse Mtn. On Saturday, avalanche workers at Mission Ridge triggered cornices and small avalanches in recent snow with explosives. 

On average, you could expect about 6-12 inches of new snow resting on the Christmas Crust at mid and upper elevations. At lower elevations and on the eastern edge there may be less. Expect to hit this 'bottom', and travel could be very slick and slippery. The crust takes the form of an impenetrable ice lens from many hours of freezing rain in many areas. At higher elevations and near the crest, the crust is more opaque and breakable, and may be covered with more snow. It'll be worth keeping an eye on this stratigraphy moving forward into the year.

Last week observers found significant dry snow below the crust and a well-preserved faceted layers in the mid and base of the snowpack. These persistent weak layers showed the potential for initiation and propagation in snowpack tests. Triggering a deeper avalanhe on one of these layers is unlikely because it is below the thick crust. However, the thickness of this crust may wane as you travel further north and east in the zone. There could still be isolated pockets of terrain where a large trigger, such as a snowmobile, could initiate an avalanche on deeper layers. Therefore, it could be worth digging down to look for weak, faceted layers.

If you make it out to enjoy the mountains, consider submitting an observation!

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