Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

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

Expect dangerous conditions with 2ft thick slabs that could be triggered in surprising ways, and run on faceted snow over a crust. A plume of subtropical moisture will bring stormy weather with rapid warming, heavy precipitation, and result in increasing danger as the day progresses. Consider starting early, ending early, and give steep slopes a wide berth. 

Avalanche problems

  • Storm Slabs

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

    At mid and upper elevations you'll find about 2ft of new snow sitting on older weak surfaces. This could be surface hoar or near surface facets on a slick crust. The sensitivity of these slabs have been decreasing slowly since Saturday, but with the incoming storm it may not take long before slabs once again become easier to trigger. Due to the nature of the weak layer, there is potential to trigger avalanches from a distance, from the edges of slopes, or from below. Slides could propagate impressive widths, and any ride could be fatal.

    Despite the stoke for winter and new snow, avoidance of large, steep slopes is still prudent as we head into the last punch of this significant set of storms. It is likely we'll start seeing large natural avalanches at some point overnight Monday and/or on Tuesday. Remain suspicious of small slopes that could push you into buried rocks or creek beds. The shallow coverage beneath the new snow could make for a nasty ride, or deeper burial.

    (12/2/2023)

    Ski triggered avalanche in Orion Chute sent the skier for a short ride. Luckily no injuries resulted. SS-ASu-D1.5-O

  • Loose Wet

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

    Rapid warming and a mix of snow, slush and rain are expected during the day. You'll likely find a surface crust in many areas in the morning, but this may break down during the day. Once you find wet, heavy snow or see fresh rollerballs, then expect potential for wet avalanches. Slides may gain mass on continuous steep slopes and create large, chunky debris piles. 

    The timing of the incoming storm and associated warmup will play a key role in this instability. Look for signs of wet avalanches which are rollerballs and fresh point release slides. These should clue you into dangerous conditions on slopes of lower elevations. If you see these, then steer clear from steep slopes.

    Example wet loose avalanche from last season.

    Photo: Matt Primomo

Avalanche Discussion

The incoming system will probably bring a natural avalanche cycle to many elevations of the zone. Needless to say, if you do head out on Monday, make sure to get back safely as it would be a very stormy night out.

Sunday was fairly quiet from an observation standpoint. An observer at SPMR reported whumphing collapses on lower elevation north facing slopes, but generally less reactivity than Saturday. Light freezing rain and rain created a crust up to mid elevations. On both Friday and Saturday observers found very reactive instabilities. On Saturday many widespread natural avalanches were reported, along with widespread shooting cracks and whumphing. Most of the slides ran on a weak interface including surface hoar and/or facets over a slick crust, and propagated impressive distances across entire features. The whumphing collapses came with reports of notable drops, and may be from the crust failing on weaker snow beneath it. This layering setup adds a large amount of uncertainty, and it's advised to treat each slope as guilty until proven innocent. 

Storm totals are up to 32" with 3.75" of water equivalent. The storm cycle began on Thursday when light, low density snow covered up various weak layers that sat around, rotting for the latter part of November. These include surface hoar sitting directly on a slick rain crust that extents up to at least 6,500ft. The crust itself ranges in thickness and supportability from stout and slick on due south facing slopes, to brittle and decomposed on northerlies. Before this week's storm, snow cover was minimal to nonexistent below 4,500ft, especially on sun-exposed slopes. Depending on where you go, the chance to hit buried rocks, logs and other obstacles may still prove a significant hazard. 

There are many great observations from the weekend to check out on our obs page. You can also add to the forecast! Please let us know what you see in the mountains by submitting an observation.

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