Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A winter storm will bring dangerous avalanche conditions across the East Central Mountains. Avalanches would break 1-3 ft deep and wrap around terrain features if they fail on weak snow above a crust. This stormy pattern will be a good reason to stick to sheltered slopes below 30 degrees. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–2.5

    New snow will continue to stress multiple weak layers in the upper snowpack, most notably the Early February Crust. With 1-2 ft of new snow (.5-1.00 SWE), the forecast team thinks we'll start seeing more activity on this weak snow now buried 1-3 ft below the surface. So far, forecasters and observers have found this structure to exist on most slopes above 5000 ft. It was also responsible for a close call in the Teanaway drainage where a group triggered a D2 on a W aspect @ 6200 ft ( Obs here). 

    Heavy snowfall and significant loading will certainly not help matters. 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. Monday is shaping up to be a dangerous day for mountain travel across the zone, so stick to well-supported, sheltered slopes below 30 degrees. 

    (2/22/2024)

    You could trigger similar avalanches on Monday, they'll likely just be bigger and more destructive. 

    The crown of a skier triggered avalanche, size D2, 4"-1.5' deep. It was triggered from below on a 30-degree terrain, and ran on facets above the early February crust. Longs Pass, W, 6,200ft

  • Storm Slabs

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

    New snow will stack up, likely creating instabilities within the new snow and wind drifted areas. The heaviest precipitation rates will come during the early morning hours, so you may find the most reactive conditions during the first half of the day. As you travel through the new snow, be on the lookout for signs of instability, like cracking or small slabs on test slopes, to help you gauge the reactivity of the new snow. With a complicated snowpack with multiple weak layers present, consider sticking to simple terrain out of the wind. 

    (2/16/2024)

    An example of a storm slab in sheltered terrain. 

    Photo: Mt Hood Meadows Pro Patrol

Avalanche Discussion

The East Central mountains will join the storm party Sunday night into Monday. As usual, we're looking at a wide range of precipitation totals across the zone. The western edges are forecast to receive over 1 inch of SWE, while the Wenatchee's may only see .25 SWE. Regardless of location, the new snow will fall on a cooling trend and should improve travel conditions significantly. It will also start testing weak layers in the upper snowpack. Beyond slab avalanches, keep loose snow avalanches in mind as well, especially if the sun pokes out. 

Our snowpack has become complicated throughout intermittent dry spells in February. There are multiple potential weak layers in the snowpack, all the way down to the early February Crust. This crust may be up to 2ft deep in some areas, and it'll be getting buried deeper on Sunday. There are also potential layers of surface hoar and faceted grains from the 11th, 14th, 18th, and the 24th. The upcoming storm and stormy week should begin to test all of these weak layers.

On February 22nd, a party of skiers in the Teanaway drainage triggered a slab avalanche on a layer of 1-2mm facets just above the early February crust. The large (D2) avalanche occurred near Longs Pass, on a W aspect at 6,200ft. It 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. This is a good example of the types of slides we're likely to see more of this week.

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