Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

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

It will be easiest to trigger avalanches in the new snow above treeline. There's still a chance that you may be able to trigger large avalanches on older weak layers at middle and upper elevation. With the uncertainty, put a extra space between where you travel and large, unsupported terrain features.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Winds may have been strong enough to form subtle drifts and thicker slabs on leeward slopes. Wind transport may drop off after morning. Look for stiffer, dry snow surfaces or hard-over-soft layering in the recent snow. Avalanches may be bigger and more likely above treeline. steer around pillowed or wind-sculpted features. Watch for shooting cracks and test slopes that slide easily. If you see these clues, stick to slopes under 35 degrees. In wind-sheltered terrain, you can trigger small loose avalanches in the new snow. If the sun comes out, expect loose avalanches on steep, southerly slopes.

    (1/5/2023)

    An example of a triggered wind slab avalanche from last week. Liberty Bowl, SW, 7,450ft.

    Photo: NWAC Public obs

  • Persistent Slabs

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

    Put plenty of space between where you travel and large unsupported start zones and shallow areas near rocks and cliffs. While these avalanches are harder to trigger, a weak layer of buried surface hoar still lurks 2 feet below the surface. You're most likely to find it in wind-sheltered terrain and sparse trees. Watch for long shooting cracks and audible collapses as you travel. 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 the past week, four avalanches have involved older weak layers: 1/8- a skier was caught in a slab avalanche near Varden Creek. 1/10- a skier triggered slab avalanche N, 4,800ft near Silverstar Creek. 1/12- A snowboarder triggered slab avalanche on SE, 6,180ft, Cutthroat Creek (see photo). 1/15- A snowmobile triggered slab avalanche on facets near the ground. While there's much uncertainty, all of these avalanches appear to have run on older layers of snow. The most likely weak layer in the western half of the zone is buried around January 5th, potentially surface hoar. While less likely, there's also weak snow around the Christmas crust as well as on the ground in the eastern mountains. These avalanches are red flag clues to use caution and assess the snowpack.

    (1/12/2023)

    Avalanche crown. Triggered while traversing a ridge and experiencing a whumphing collapse. ~2ft deep by 100ft wide. SE, 6,180ft.

    Photo: Ben Starkey

Avalanche Discussion

On Monday, observers at 6,200ft, NW in the Hairpin valley reported sudden and propagating test results on the Jan 5th surface hoar, 2 feet (70cm) below the surface. The results were very hard (beyond the limits of standard tests) and the surface hoar was small and rounding (0.5mm). They also reported moist snow, but no crust in in the upper layers. On Sunday, observers in the Highway 20 corridor near Washington Pass reported blowing snow above treeline along with loose dry avalanches in steep terrain. At least one of these triggered a small slab avalanche. 

A significant cycle of wet avalanches occurred on Friday into Saturday in the lowland hills. Large wet avalanches gouged to the ground on a west aspect around 4,000ft of Pole Pick Mountain, east of Twisp. On Saturday, an observer near Driveway Butte reported hearing avalanches running and saw very large wet avalanche debris. Friday morning, I saw a couple of small wet avalanches that ran to the ground on a steep bank north of Methow (see below). WSDOT forecaster reported a wide avalanche (~600ft) in the SR 153 corridor near Carlton. An observer reported that a large avalanche put debris on Twisp River rd near the intersection of Poorman's Creek rd. Observations in the higher into the mountains are still limited. If you see avalanches, please submit an observation.

On Thursday, I went to the Twisp River drainage to look for persistent weak layers. While we didn't find anything that obviously pointed to the danger, we trigger surface instabilities and saw the beginning of the warm up. At 4,900ft, north aspect, we found tilt tests failing down 10" on an interface from around January 5th. This layer could harbor surface hoar in other locations. We found sudden planar tests and propagating results within the Christmas crust matrix (CTM (SP), ECTP 31).

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