Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

A storm is bringing over 6 inches of snow to the zone by the end of the day Wednesday. Combined with strong to extreme winds and warming temperatures, avalanches will be very likely, especially at higher elevations. Everywhere you travel, avoid steep slopes, but as you work your way towards upper elevations, avoid all avalanche terrain, including flat and lower-angle terrain beneath steep slopes as well. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    Snowfall will start Tuesday night and continue through the following night.  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.

    Stay off all avalanche terrain including low-angle surfaces beneath steep slopes as you make your way towards higher elevations and new snow depths increase. In all areas, avoid steep terrain on Wednesday. Winds will reach extreme, so most areas you travel will likely be wind-affected. Wind-loaded slopes will likely break easier than non-wind-loaded slopes. 

    Eample photo: A storm slab avalanche like one you might see or trigger on Wednesday. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2.5

    Triggering a 1-3 ft thick avalanche is 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 6-14 inches of new snow across the zone, the forecast team and strong winds, we expect that you'll see 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 persistent slab avalanche on a west 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.

    (2/22/2024)

    A skier triggered avalanche (D2) on facets above the early February crust in the neighboring East Central zone. The crown was 100' wide x 4"-1.5' deep and it was triggered from below on a 30-degree terrain. It ran to either side of the low-angle slope. Longs Pass, W, 6,200ft

Avalanche Discussion

We've had a lull for the last day in the East South zone before the next storm enters on Tuesday night. This storm will feature warmer and wetter conditions which will undoubtedly increase avalanche danger during the evening hours and into Wednesday.  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.

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).

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