Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Despite the calmer weather, you can still trigger wide avalanches big enough to bury people in this zone. You'll want to give the new snow time to settle out. Continue to seek out sheltered slopes out of the wind that are below 30 degrees. 

Avalanche problems

  • Storm Slabs

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

    The new snow still needs time to settle. Slabs could break within the new snow, at the old snow interface, or even deeper on a number of weaker layers at higher elevations. The new snow recently buried a layer of facets and surface hoar on sheltered, shaded slopes above 5,000ft. If you find one of these areas, slides may fracture widely or be triggered from adjacent slopes. As you travel, look for signs of instability such as cracking in the new snow, test slopes releasing easily, or hear whumphing collapses. Default to less steep terrain if you find more than 6 inches of new snow and notice obvious signs of instability above. 

    Loose snow avalanches: 

    We have a lot of low-density, cohesionless snow. If skies are sunnier than weather models predict, we may see some surficial sun-induced loose snow avalanches. Most avalanches should be relatively small, but some could be large enough to knock you over and carry you where you don't want to go. 

    (2/16/2024)

    An example of a small storm slab in sheltered terrain

    Photo: Mt Hood Meadows Pro Patrol

  • Persistent Slabs

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

    Triggering a 1-3 ft thick avalanche remains likely. Incremental snowfall and significant loading will continue to stress multiple weak layers in the upper snowpack, most notably the Early February Crust. With anywhere from 4-12 inches of new snow across the zone, the forecast team thinks we'll start seeing more activity on this weak snow. So far, forecasters and observers have found this structure to exist on most slopes above 5000 ft. This weak layer was already responsible for a close call in the Teanaway drainage where a group triggered a D2 on a W aspect @ 6200 ft ( Obs here) last week. 

    You'll generally find the largest slabs in wind-loaded terrain, but we're getting to the point that any steep slope, even in sheltered areas, should be considered suspect. Avalanches could break widely across terrain features and easily be large enough to bury or kill you. 

    If your primary goal is to not get caught in an avalanche, staying off of and out from below steep slopes is the most reliable way to reduce your risk.

    (1/6/2021)

    An example of a persistent slab from past years near Mission Ridge. You could trigger similar-sized avalanches on Tuesday, especially adjacent to ridgelines that receive wind loading. 

    Photo:Mission Ridge Pro Patrol

Avalanche Discussion

Monday was a stormy day across the east-south mountains. Observers across the region reported excellent powder riding and gusty winds at higher elevations. The Mission Ridge Pro Patrol reported triggering shallow propagating soft slabs in more sheltered pockets during avalanche mitigation work. They reported these slabs failing on recently buried surface hoar. Weather stations across the zone reported anywhere from 4-10 inches of new snow, with areas near Bumping Lake and west receiving the most.

Tuesday is shaping up to be calm before another potent storm comes crashing into the region in the evening hours. This storm will feature warmer and wetter conditions which will undoubtedly increase avalanche danger during the evening hours and into Wednesday. 

Since February 14th, storms have brought over 20 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).

 Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

 

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