Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The start of the day may not feel all that dangerous, but look for avalanche danger to increase during the afternoon and evening hours. New snow and radical wind speeds will create reactive slabs primed for human triggering. Avalanches could grow large and break across terrain features if they fail on weak snow above a crust. Default to more wind-sheltered slopes less than 30 degrees for safer travel alternatives, especially during periods of heavy snowfall. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    New snow and strong winds will combine to create our first batch of wind slabs for this storm cycle. Precipitation and wind speeds will only increase as the day matures, so look for these slabs to grow in size and sensitivity throughout the day.

    These slabs will form on the lee-side of ridges, below cornices, adjacent to rock and cliff bands. Unfortunately, much of the zone has a weak upper snowpack, so expect increased reactivity and surprising avalanches if wind slabs step down to weak snow above the early February crust. This setup will make for a heads-up day to be traveling in wind-exposed terrain. Pay attention to blowing snow, wind-textured surfaces, or sharp drifts to help you identify where unstable slabs could exist. 

    (2/22/2024) Photo: Julz Holder

    You could trigger similar avalanches on Sunday. 

    The crown ranged from ~4" thick to 1.5'. The persistent slab in this location was associated with old wind slab from east winds; counter to the more recent loading patterns.

Avalanche Discussion

Sunday will mark the first day of a stormy period. It should take some time for precipitation to initially reach the East South, but once it does, we expect rates to intensify and winds to increase into the strong range. The forecast team expects dangerous avalanche conditions to develop during the late afternoon/evening hours. 

Just to the north in the East Central zone,a group traveling in the Teanaway drainage triggered a slab avalanche on a layer of facets just above the early February crust. The large (D2) avalanche occurred near Longs Pass, 6,200ft, W was triggered from a lower-angle, 30-degree slope near a cluster of trees. A crack propagated uphill and across in both directions. The avalanche ran to either side of the lower-angle feature and didn't involve the party that triggered it.  You can check out their full observation here. This close call may be a sight of things to come.

Since February 14th, storms have brought 14-16 inches of snow to the East South zone. In much of the region, this new snow now sits over persistent weak layers of faceted snow over the slick Early February Crust (EFC). Observers in many areas of the Cascades, including in an NWAC forecaster in the Darland Mt area last week, have found weak, faceted snow just above the stout EFC crust and also over a thin, breakable crust buried on 2/14 on southerly aspects. This persistent weak layer has produced avalanches in neighboring zones (observation here). Since February 15th, 13 unintentionally human-triggered avalanches have failed on or just above the EFC throughout the Washington Cascades. We have reports of avalanches on all aspects between 5000ft and 8000ft. It has been a number of days since the last reported avalanche, but these problems can be tricky and linger in certain spots like steep, rocky terrain with a shallower snowpack.  

Expect a very thin snowpack at lower elevations and on some steep southerly slopes. Slick crusts, exposed obstacles, open creeks, and bare ground continue to make travel more adventurous. 

 

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