Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

You may encounter small loose avalanches on steep, sunny slopes and you may be able to trigger slab avalanches where the wind drifted snow above treeline.  It's now difficult to trigger avalanches on older weak layers near the Cascade crest. With the uncertainty of these dangerous avalanches, it's still a good idea to put an extra buffer of space between your group and big, open slopes above rocks or cliffs.

Problemi valanghivi

  • Wind Slabs

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

    Steer around smooth pillow-like drifts on steep leeward slopes.  You can also choose lower-angled portions of a slope or entrances off of ridgelines to avoid triggering a wind slab avalanche. Blowing snow can point to which aspects are being loaded.  If you see red flag signs like shooting cracks or new avalanches, choose lower-angled or wind-sheltered terrain. The wind was strong enough to transport snow on Sunday and more northwest wind could build slabs at upper elevations on Monday morning. 

    (1/5/2023)

    Cracks shoot through wind-drifted slabs just below a ridge. 

    Photo: Frank Clements

  • Loose Wet

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

    The sun will warm steep, southerly slopes, where you may see some small loose avalanches. Southeast aspects will get warm and weak first and southwest aspects will be more prone to avalanches in the afternoon. Watch for moist snow surfaces and rollerballs as indicators before an avalanche occurs. If you see these or other recent wet avalanches, move to lower-angled or more shaded terrain. Don't linger under steep rocky terrain, as natural avalanches could come down from above.

    (1/20/2023)

    Wet loose avalanches were easy to spot on sunny south aspects Friday. One large wet loose is visible in the right gully. 

    Whistler Mt

    Photo: Katie Warren

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2.5

     While triggering these dangerous avalanches is unlikely in much of the zone, it's a good idea to use caution if you're traveling to the higher mountains east of Mazama.  Put plenty of space between where you travel and large unsupported start zones and shallow areas near rocks and cliffs.  If you experience audible collapses, stick to slopes less than 35 degrees.

    Depending on where you traveling in the zone, you'll need to adjust your travel practices.  In the mountains east of Mazama and above 4,500ft, you need to have a more conservative mindset. Digging snow pits and looking for propagating test results can help you identify weak layers in the top 2-3 feet of the snowpack. You can find the main layer of concern, the January 5th surface hoar, as a stripe about 2 feet below the surface. See the discussion below for more details

    (1/19/2023)

    Crown lines from a recent Avalanche near Clark Peak (Tiffany Mt area). Probably released on buried surface hoar. (N 6900', HS-N-D2-R2-O)

    Photo: Willie Webster

Avalanche Discussion

On Sunday, observers triggered a small avalanche in a pocket of freshly drifted snow at 6,900ft, SE aspect near Snagtooth Ridge. On Thursday, observer Willie Webster traveled to the Tiffany Mt area and found what is likely the Jan 5th surface hoar layer about a foot down.  This layer produced recent avalanches, collapses, and propagating snowpack tests (check out the video below). 

The January 5th buried surface hoar is the main persistent weak layer that we've been tracking in the zone. Near Washington Pass, it's  ~2' below the snow surface and is becoming unreactive.  It hasn't been involved in any human-triggered avalanches since 1/12. Willie's observation, near Tiffany Mt indicated that triggering avalanches on the 1/5 SH is far more likely in this portion of the zone. On Wednesday, Willie went to take a look at the very large slide that occurred in Liberty Bowl/Blue Lake Pk that likely occurred on January 13 or 14th. The avalanche failed on the Christmas Crust and stepped down to the mid-November facets (11/22).  A crown depth of 5-8 feet was measured.  While this avalanche was an anomaly, a look through the depths of our database shows other natural avalanche cycles on these layers.

A significant cycle of avalanches occurred last week (1/13 and 1/14)  with wet avalanches in the lowland hills gouging to the ground and multiple very large natural avalanches running on persistent weak layers. Check out the media reel below and our observation platform to see more media of the impressive slides. 

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