Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

You can trigger avalanches where new snow and wind build fresh slabs at upper elevations. Watch for blowing snow and cracks shooting through the snow as indicators to stick to wind-sheltered terrain or slopes less than 35 degrees.  As you may still be able to trigger large avalanches on older buried weak layers, put extra space between where you travel and large, consequential pieces of terrain where avalanches could start.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    New snow and wind will form fresh wind slabs near and below ridgelines on Sunday.  Steer around steep lee slopes where you find smooth pillow-like drifts and the base of cliffs where wind-blown snow collects.  Blowing snow and building cornices will give you clues as to which aspects are being loaded.  You can choose lower-angled entrances off of ridgelines to avoid triggering a wind slab in the new snow.  If you see red flag signs like shooting cracks or new avalanches, choose lower-angled and more sheltered terrain.

    (1/5/2023)

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

    Photo: Frank Clements

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2.5

    Depending on where you traveling in the zone, you'll need to adjust your travel practices. Digging snow pits and looking for propagating test results can help you identify these weak layers in the top 2-3 feet of the snowpack in western portions.  In the mountains further east, you need to have a more conservative mindset.  Put plenty of space between where you travel and large unsupported start zones and shallow areas near rocks and cliffs.  Watch for long shooting cracks and audible collapses as you travel.  Persistent slab avalanches often surprise travelers, breaking further across the slope and around terrain features and/or from lower-angled terrain.

    Near Washington Pass, the January 5th buried surface hoar layer is  ~2' below the snow surface. It hasn't been involved in any human-triggered avalanches since 1/12.  Further east, observers on 1/19 in the Tiffany Mt area saw recent avalanches on this layer, shooting cracks and felt collapses, indicating that triggering an avalanche is far more likely in this portion of the zone.  An outlier natural avalanche involved the Christmas crust and lat-November facets.

    (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 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 some whumps and indicated propagation was likely in snowpack tests (check out the video below).  Small wind slabs could be easily triggered below ridgelines on test slopes. 

Wednesday, NWAC observers went to take a look at the very large slide that occurred in Liberty Bowl/Blue L 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.  This avalanche is unusual and highlights the variability in the snowpack and how deeper weak layers can be activated during large storms. On Monday, observers at 6,200ft, NW in the Hairpin valley reported sudden and propagating test results on the Jan 5th buried surface hoar, 2 feet (70cm) below the surface.

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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