Avalanche forecast

Snoqualmie 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

This winter storm brought a pretty abrupt change to the snowpack and likely significantly increased the avalanche danger. You may find that avalanches trigger very easily at the base of the new snow. Tread carefully and steer around steep open slopes especially at mid and upper elevations.

Avalanche problems

  • Storm Slabs

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

    Avalanches could occur Monday at the base of the storm snow, on layers within the new snow, and in wind drifted areas. This storm brought a big change in the weather and with it the potential for big problems (avalanches). Even though the lure of the new snow is strong, this will be a day to take a more conservative approach. Prior to this storm plenty of weak surfaces and icy crust were observed (see discussion for more details). Predicting how any particular slope will react may be extremely difficult. At mid and upper elevations, steer around open slopes greater than 30 degrees. If an avalanche failed on persistent weak grains, it could act in surprising ways like triggering very easily, propagating widely, or failing in small openings in the trees. In more exposed locations the wind may create slabs several feet thick that will easily be large enough to bury and kill you. While you can use hand pits and small slopes to test the snow, remember “variable” was the word of choice to describe the surface this past week. Just because ‘this slope’ didn’t fail doesn’t mean ‘that one’ won’t. 

    At lower elevations, freezing rain and rain turning to snow should help decrease the danger slightly. In these locations, possible weak layers were likely destroyed by wet weather on Saturday. However, that doesn’t mean they don’t exist. Avoid steep slopes above terrain traps where even small avalanches may hurt you by pushing you over rocks or into open creeks.

    (1/29/2022)

    Small (1mm) near surface facets found "sandwiched" by a thin crust at the surface and a very strong crust underneath. This set-up was typically seen on NW-NW aspects above 4000'. 

    Photo: Dallas Glass

Avalanche Discussion

This is a tricky storm and it makes for a tricky avalanche forecast. How much snow falls after the cooldown could have a significant impact on just how dangerous conditions become. Fortunately, the highest hazard should be Sunday night during periods of intense precipitation. However, a Puget Sound Convergence Zone could keep the fire hose pointed at Snoqualmie Pass into Monday. During periods of heavy snowfall and blowing snow natural avalanches may occur. We’re expecting 8-12” at pass level with 12-18” possible at mid and upper elevations by Monday afternoon. Keep an eye on the weather. If what you see doesn’t fit with what you expected, the avalanches forecast might also be incorrect. 

Prior to this storm, numerous observations were sent to NWAC highlighting firm icy crusts, near-surface facets, surface hoar, and facet-crust sandwiches. In general, near-surface facets and facet-crust sandwiches were typically found on open slopes, even amongst sparsely spaced trees. On more southerly slopes very firm melt-freeze crusts could also be found. Spotty surface hoar was reported in the “bathtub ring” around the top of the inversion layer often above 3700’ and below 4500’. A light freezing rain event on Sunday may have destroyed weak surfaces below about 4000 feet near and east of the Pass. 

Fortunately, below this new interface, the snowpack is very strong and well settled. We don’t have any layers of concern deeper in the snowpack. So, while plenty of new potential weaklayers exists, it should be fairly easy to make observations within the new snow and at or just below the old surface. 

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