Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

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

Avalanches may increase slightly in size with more new snow over a crust, but Monday should be quite similar to Sunday. Wind slabs may lurk in the fog at upper elevations and could be large above 7000 ft.  Near and below treeline,  you're most likely to encounter shallow wet, heavy, and moist snow that you can push into a small avalanche running on the crust.

Avalanche problems

  • Wind Slabs

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

    Avalanche danger will be most elevated above 7000 ft where you're likely to find colder snow and moderate to occasionally strong winds continuing to drift snow. As you ascend, take note once the snow becomes drier. At these elevations, expect to find active wind transport alerting you to potential problem areas. However, as winds shift from S to WSW over the next 24 hours, wind-loaded slopes may cover a variety of aspects. Recent sharp cornices can help you identify the recently wind-loaded slopes and also freshly forming ones. Look for firm slabs sitting above less dense snow and test out the slab reactivity on small test slopes before engaging with larger features. You can trigger a potentially large avalanche on any wind-loaded slope steeper than 35 degrees at upper elevations. Shooting cracks or cracking snow surfaces can also help you identify the problem. Given the likelihood of poor visibility and heavy precipitation punctuating the danger at times, give yourself some extra margin for error, and simple retreat options. 

    We're not sure whether you will find true wind slabs at middle elevations, but it's possible if temperatures end up cooling off a bit.  Note the snow character. Sticky snowball snow could run on top of a crust on a very steep slope, but it's unlikely to form deeper, larger, and more dangerous drifts. 

    (1/11/2024)

    Small shooting crack in wind drifted snow. 

    Photo: Joseph Dellaporta

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Snow levels should hover around 5500 ft over the next 24 hours with the freezing line around 6000 ft. Observers reported wet snow that pushes easily on a slope cut and releases on the 1/20 crust. This was most prevalent below 6300 ft on Sunday and were less than size 1. Monday should be a rinse and repeat of Sunday, but with just enough snow atop the crust that you can trigger a real size one avalanche. While these can knock you off your feet and into terrain obstacles, they could easily bury you in a terrain trap. Consider what's below you as you traverse or ride on slopes steeper than 35 degrees. Take advantage of small test slopes to evaluate the bond between the recent snow/slush and the 1/20 crust. At lower elevations where rain may fall on dry snow for the first time, rollerballs and traditional wet loose avalanches may form.  During periods of active rainfall, reduce your exposure to slopes 35 degrees and steeper. And if you find saturated surface snow that lets your boots plunge in 6" or deeper, you could trigger a small wet avalanche.

    Even a small wet loose avalanche could do damage, particularly when paired with a terrain trap. 

    Photo: Mt Hood Meadows Patrol (4/11/23)

Avalanche Discussion

Rain and snow picked up in a major way, with over an inch of water equivalent above the 1/20 crust. This translated to 4-6" of dense wind-blown"snowball" snow from 6000-6600 ft, with 2-3" of slushy snow above the below 6000 ft. With another inch of snow water equivalent expected tomorrow with similar snow levels, expect the amounts of snow above the crust to double. This adds size and more consequence to any avalanche relative to Sunday. The silver lining is that the mild temperatures are helping instabilities heal quickly, so expect the highest avalanche danger during periods of heavier snow.  Manage the overlapping problems at the middle elevations by noting when the snow becomes drier and starts to move with the wind. Above this elevation, wind slabs are your concern, while at lower elevations, focus on the wet loose hazard.

Here's a short primer on the upper snowpack. A major storm cycle last week ended with a freezing rain event that mostly affected elevations between 4200-4500 and 6500 ft. A skiff of snowfall buried this 1/20 crust on Saturday with the additional snow load on top of it as described above. Reports indicate that drier snow may have broken down the crust below 6000 ft. A layer of consolidating cold dry snow (perhaps 5-10" thick now) sits between the 1/20 crust and a more broadly distributed 1/16 crust extending from 4500 to around 8500 ft. Most avalanche activity will involve or remain above the 1/16 crust (storm snow). Once the 1/20 crust fades away at upper elevations, a larger avalanche could involve the 1/16 interface. You can read more about these crusts in this observation from Saturday at Tilly Jane (photos in Gallery).  The crusts are broadly similar on all sides of Mt Hood. 

Inversions on Mt Hood have meant that mid-elevations have warmed more in recent days than lower elevations. Therefore, lower elevations are more susceptible to a warm-up than middle elevations where crusts already exist. This warm-up should continue over the next 24 hours with temperatures east of the mountain finally rising above freezing. 

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