Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Wind-affected snow will remain the most likely location for you to trigger an avalanche on Thursday. Slabs may be larger in areas that receive more significant snow totals, but any avalanche can have an undesirable outcome in consequential terrain. If you suspect a slope is wind-loaded or see red flag signs of instability such as whumpfing collapses or shooting cracks, head for lower angled slopes under 35 degrees.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Additional snow and wind should help to thicken any pre-existing slabs or build fresh slabs throughout the West South zone. Although the largest and potentially more sensitive slabs could be found on leeward slopes at upper elevations, don’t overlook smaller features well below ridgecrest that are prone to wind-loading. Be leery of areas such as convex rollovers, confined chutes and gullies, or the base of cliffs. Uncoincidently, these are the same areas where avalanches often like to initiate. Take a look for textured surfaces or smooth pillow-like piles of snow to help you identify wind-loaded slopes to avoid. Using uptrack tests or small test slopes as you travel is a quick way to look for potential weak layers or slabs. If you suspect that a slope is wind loaded or find that blocks of snow are failing easily in your tests, head for slopes under 35 degrees.

    A poor snowpack structure has been identified in some areas of the zone. More details surrounding this layer are in the discussion below, but you should be aware of the possibility of isolated avalanches breaking in surprising ways.

    (1/31/2022)

    This small wind slab was intentionally triggered by a skier on a NE aspect around 6300'. The avalanche failed at the new-old snow interface. HS-ASc-R1-D1-I. 

    Photo: Shane Robinson

Avalanche Discussion

Observations have been a bit limited around the zone since we returned to winter on Sunday night, but reports from both the Crystal and Rainier areas indicate that the wind has been a major player. Textured surfaces, sensitive slabs, scoured windward slopes, and freshly building cornices have all been observed. Snow totals were varied across the zone with the volcanoes receiving more water than areas closer to the crest. Expect this trend to continue as another wave of precipitation impacts the zone Wednesday night and Thursday. This could result in smaller and more manageable avalanche problems in areas closer to the crest, but don’t underestimate the ability of the wind to take small snow totals and turn them into larger avalanches. The recent snow has been reported to be moderately bonded to the underlying Late January Crust (1/30) and in some cases, a poor bond has been identified. 

At Crystal Mountain, NWAC forecasters on Tuesday identified a weak snowpack structure around this Late January Crust. A facet-crust combo was found on most aspects that do not contain a southerly component. This layer has not been positively identified by NWAC in other areas of the zone as of yet, but NPS Rangers reported some whumpfing collapses on Tuesday. As we incrementally increase the load atop this layer, it’s a bit of a waiting game to see if it starts to produce avalanches. Our sense is that the new wind and snow on Wednesday night and Thursday will not be enough to tip us over the edge, but you should be sure to do your homework before stepping into consequential terrain, particularly in areas with larger snow totals. Avalanches that fail on persistent grain types can act in surprising ways and span farther distances than you’re used to, connecting terrain features or breaking above you. Due to this layer’s uneven distribution, you could find that different areas of the zone or even adjacent slopes are behaving very differently. If you’re out and about and notice this layer in your pits or whumpfing collapses as you travel, please let us know by submitting a public observation.

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