Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Very large slabs may release naturally from the upper slopes of Mt. Hood. Stay out of large avalanche paths or large open areas in canyon bottoms where avalanches may start, stop, or run. At lower elevations, slabs will be reactive to human trigger on slopes steeper than 35 degrees.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Winds and fresh snowfall will continue to build denser slabs over low-density snow from earlier in the storm cycle. Expect the risk of wind slabs to increase throughout the day. With an ongoing storm cycle since Thursday, some of these avalanches could be very large. Near treeline, wind slabs may be small-large, but should still be widespread. Give avalanche terrain at upper elevations a wide birth as this storm and avalanche cycle continues.  Avoid large avalanche paths where an avalanche can start, run, or stop. This includes valley bottoms where avalanches may reach from above. Near treeline, stick to smaller terrain features and avoid wind-loaded terrain steeper than 35 degrees.

    (4/10/2019) This very large wind slab avalanche in April 2019 gauged deeply and ran into significantly lower elevation terrain. Note the stunted trees and open terrain in the photo and avoid similar terrain on Monday.

  • Storm Slabs

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

    Storm slabs will be primed for human trigger on Monday. Continued warming combined with heavy snowfall may overload low-density storm snow from earlier in the storm cycle while multiple mid-strom interfaces should be reactive as well. Seek out smaller, lower angled, and treed slopes. Avoid all open slopes steeper than 35 degrees. You can use small unsupported test slopes to confirm the problem in your terrain.

    (2/13/2021) Tree-bomb triggered storm slab indicating very unstable snow.

Avalanche Discussion

As the snow keeps piling up, the very real threat of Snow Immersion and Suffocation (SIS) increases. If you recreate in forested areas, travel with a partner and maintain visual or audio contact. 

Storms have been unrelenting on Mt. Hood with 34" of snowfall since Thursday. The snow was very cold and low-density through Saturday morning, but a very rapid warm-up triggered widespread small natural storm slabs on Saturday as denser slabs began building.  NWAC professionals observed tree-bomb triggered avalanches at unusually low elevations (5000 ft).  A public observation from Bennet Pass documented widespread crowns on steep, convex rollovers. On Sunday, freezing rain created a quarter-inch freezing rain crust on the south side of the mountain. Meanwhile, on the north side of the mountain on a NE aspect at 6000 ft, the freezing rain crust was not present and an observer found reactive snowpack tests on a weak snow interface that pre-dates the storm cycle (2/11). In some areas, the 2/11 interface may involve a thin freezing rain crust.   An observation from Newton Canyon found this surface crust even on NE aspects below 6000 ft. 

Winds in the storm cycle have thus far peaked on Friday with very strong to extreme gusts. Significant wind loading has created the potential for very large avalanches above treeline and above the NWAC forecast bands. Due to limited visibility, we have been lacking observations at higher elevations for several days. 

The stout mid-January crust is considered the new "ground" with a strong snowpack structure in place below this layer. Weak and faceted snow just above the stout rain crust was responsible for a number of avalanches last week, but no new evidence of avalanches on this interface suggests these facets are gaining strength. This weak layer (which is similar in structure to the fatal avalanche in WA)  still exists around Mt Hood and could produce a very large avalanche, but no evidence of recent avalanches on this layer have been reported.

Headed north to recreate?  We have a tricky snowpack with persistent slab problems in all forecast zones across the state line.  Take the time to read about the different snowpacks that have developed further north and adjust your terrain selection accordingly. 

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During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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