Avalanche forecast

East Slopes North

Northwest Avalanche Center
View on map

Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Quieter weather has allowed the snowpack to begin to heal since heavy snow and rain fell at the beginning of the week. You may still be able to trigger very large and deadly avalanches on deeply buried weak layers on northerly aspects near and above treeline. Watch for triggering avalanches in wet snow or recently formed storm layers. 

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2.5–3.5

    Continue to put a wide buffer between where you travel and large start zones and avalanche paths that are suspect for this dangerous avalanche problem. If you hit the trigger point for the persistent weak layer, the resulting avalanche could be destructive and unsurvivable. These avalanches may give little warning and may be difficult to trigger on some slopes. You may be able to trigger them easier near Harts Pass and drainages east of the Cascade crest.

    While the late January facets had been dormant, they've remained weak on shaded aspects at middle and upper elevations. A huge load of recent snow has now made it easier to trigger avalanches. A few deep natural crowns in the Hairpin valley and an avalanche triggered near Hart's Pass on March 3rd (see photo and details below) suggest that this layer may have been reactivated during the last storm. You can find this layer about 5ft deep and sandwiched between two crumbly crusts. Sudden or propagating results in snowpack tests can help you identify the layer. Further east it's closer to the surface and not far below the most recent storm interface from Feb 26th. 

    (3/3/2022)

    A very large (D2.5) and widely propagating slab avalanche was triggered by a snowmobile on March 3rd. The crown is estimated at roughly 5ft deep. 6600-6800ft, NE, near Harts Pass

    Photo: Drew Lovell

  • Storm Slabs

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

    Use caution around slopes 35 degrees, especially on leeward sides of ridges. Steer around convex roll-overs and unsupported slopes. Recent storm snow still needs time to bond due to an unusually weak new/old interface. Wind since March 1st drifted shallow slabs at upper elevations.

    Widespread, very large avalanches occurred on Monday in the storm snow. While the natural activity has ended, you could still trigger these avalanches. A weak layer of facets and surface hoar was buried on the 26th and could still be triggered by backcountry travelers. Pay extra attention to sun-exposed southeast through southwest aspects, where the facets may rest on a crust and could be extra reactive. Manage the risk by minimizing your exposure to avalanche terrain. 

    (3/1/2022) A deep crown of a slab avalanche at the base of cliffs. SE, 6500ft near Azurite Pass. Photo: Steph Williams

  • Loose Wet

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

    Shallow accumulations up to 5 inches could slide easily on steep sunny slopes. Rain fell to 6,500ft, leaving a lot of heavy, mushy snow. You can trigger deeper wet avalanches in the recent snow on slopes 35 degrees and steeper where snow is wet and unsupportive. If surface crusts melt and become weak and punchy, move to lower angle or shaded slopes. Rollerballs and wet, unsupportive snow are indicators that you could trigger wet avalanches. 

    (1/26/2022) Example of wet avalanches from Jan 12-22th. SE-NE, Whistler Mtn and Cutthroat Peak Photo: Josh Hirshberg

Avalanche Discussion

Heavy snow, rain, and difficult travel limited access and information. On Thursday, observers reported another 3-5 inches of snow in the past 24 hours. They reported a widespread cycle of avalanches that occurred 2/28-3/1 up to size D3. They also reported tests on the late January facets (about 5 feet below the surface) and the February 26th facets (under the recent storm) indicate the potential for human-triggered avalanches. Near Harts Pass, observers measured 55" of storm snow which settled to about half that height by March 1st. The weather station at Washington Pass recorded an overall gain in height of snow  38" between the 26th and the afternoon of the 28th followed by rain to 6,500. Enough rain fell to create moist to wet snow surfaces and difficult travel. Cooling temperatures should form surface crusts.

The storm brought a widespread cycle of large to very large avalanches across the zone. NWAC Forecaster, Matt Primomo, reported a couple of crowns on steep, unsupported slopes in the Hairpin valley that were deep enough to involve the late January facets. On Thursday, a snowmobile triggered a very wide slab avalanche, at least D2.5, at 6600-6800ft, NE, near Harts Pass. While we don't know for sure, the crown is estimated to be 5ft deep and may have run on the late January facets. On Tuesday, observers reported triggering a small avalanche, about 1 foot deep on an E-SE aspect at 7,000ft near Harts Pass. The slide started as wet loose that then broke into a slab 10-15 feet wide. Near the Silverstar trailhead, I found the February 26th facets preserved under almost 2 feet of recent storm snow and resting on a crust. Snowpack tests produced sudden results (CTM (SP)) on the layer. Numerous avalanches to size D2.5 occurred on S-SE aspects of Delancey ridge. It appeared that some ran in dry snow on Monday with wet avalanches running later in some of the same paths. On Monday, observers near Harts Pass reported widespread natural avalanches in the new snow, even on small, low-angle features and paths that don't frequently avalanche. By the evening of the 28th, they reported 3 feet of accumulated storm snow. 

On Sunday, observers in the Cutthroat creek area found touchy avalanche conditions in the early storm snow and tests that indicated the potential for triggering the late January facets. One large soft slab up to 1.5ft deep was noted from a SE aspect at 6,700ft. On a similar slope, observers reported remotely triggering a slab avalanche, likely on the 2/26 interface. Numerous small (D1-1.5) loose avalanches were also observed from upper elevations. 

Regions covered