Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Sunshine and late-spring temperatures will go to work to destabilize steep slopes maintaining cold recent snow.  Reduce your exposure to mountain hazards such as cornices and precarious chunks of snow. Slabs will be stubborn, but their size warrants caution around very steep, heavily loaded terrain features.

Avalanche problems

  • Loose Wet

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

    Temperatures continue to climb on Mt Hood and recent dry snow remains susceptible to strong April sunshine as freezing levels approach the top of the volcano. The risk of wet loose avalanches may expand on shaded aspects and into upper elevation terrain. The nature of the wet avalanche activity likely differs with altitude. At the highest elevations, chunks of snow falling off steep, cliffy terrain represent a hazard in their own right, but can also entrain moist snow on the slopes below. Exposed ridgelines likely developed large cornices during the last storm cycle that could fail without warning. At lower and middle elevations, a thin crust likely formed on the snow surface by Saturday above around a foot of recent dry snow. As the crusts break down, the snow in more sheltered terrain may become moist and heavy. Expect the potential for rollerballs, and generally small wet loose avalanches  on slopes steeper than 35 degrees. NW and NE aspects that were recently shaded are starting to experience sunshine as we head later into the spring. Don't discount the potential for these aspects to start producing avalanches if previously dry snow becomes sticky and gloppy.

    Reduce your exposure to steep slopes which may be above you during this time of rapid transition. Avalanches are likely to slide efficiently atop the 3/31 crust. Although they may start slowly, they can gain steam and mass quickly as they head down the slope.

    Example: Wet loose activity on steep, rocky features shedding precariously perched snow.

    Photo: Joe Dellaporta

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–2.5

    Mt Hood Meadows Pro Patrol triggered wind slabs each of the last 3 days with the largest slab (size 2.5) triggered early Friday, following the most intense winds of the storm cycle on Thursday. The most recent slab development is less than 2 days old, but we expect these  hard slabs will be very stubborn to trigger by Saturday. Most of the slab reactivity was in the 6000-7000 ft range and failed on a hand hardness change on top of the 4/1 interface (a few inches above the 3/31 crust). Extreme winds rendering the highest elevation snow mostly unreactive while sunshine and warm temperatures have likely accomplished a similar task at lower elevations and on sun-affected slopes. Given the potential size of the avalanches, you're well served to steer around steep, heavily wind loaded terrain at middle and upper elevations on shaded or E aspects. Slabs could exist well below ridgelines. With many slopes scoured back to the 3/31 crust, it should be possible to identify areas of wind drifted snow. Steer around the edges of these wind deposits. In some cases, you may find intensely mottled sastrugi (wind scour), which should be unreactive to human trigger, but may not make for good riding. If you choose to engage with more consequential terrain on wind loaded aspects, it's worth evaluating the 4/1 interface and the firm slab it supports on a test slope before committing. It's worth noting that although these slabs are unlikely to be triggered by humans, a large cornice fall could be the impetus for one to wake up.

     

    Example: Expect a variety of wind sculpted and and wind loaded surface textures on Saturday.

    Photo: Ryan Matz

Avalanche Discussion

Saturday will be much warmer than average and a sharp temperature departure to the cold, snowy conditions in recent days. The silver lining is that we're expecting a decent overnight refreeze thanks to clearing skies. Expect wet avalanche activity to be minimal to start the day, but will ramp up as the sun hits slopes, with reactive snow surfaces shifting around the mountain throughout the day. You may be tempted to forget about the recent slabs, but they still lurk on shaded and E aspects. 

Tuesday through Thursday brought 1.6" of water equivalent to the mountain and increased the base depth from 51" to 60" at Mt Hood Meadows with the most significant snowfall Wednesday night. Moderate snow shower activity continued at times through Thursday morning, decreasing during the afternoon hours as winds ramped up to a sustained 40-50 mph range. These winds transported intense plumes of snow into the evening hours. The winds relented in the late evening hours. Friday brought mostly sunny skies with temperatures rising above freezing at most NWAC forecast elevations. The Mt Hood Meadows ski area experienced 2" of snowpack settlement in the past 24 hours. A D1 natural wet loose avalanche in Accordion at Mt Hood Meadows illustrates the impact of the warmth and sunshine. Expect further settlement of the upper snowpack and the potential for more, mostly small wet loose avalanche activity on Saturday.

Although the snow conditions should be someewhat improved after the recent snowfall, expect a variety of snow surfaces including breakable crusts, firm crusts, and sastrugi. Windward aspects and ridgelines remain stripped to the 3/31 crust or ground. The 3/31 crust was notably slick prior to the recent storm cycle at upper elevations, so make sure you have the tools and the skills to arrest a fall on steep, icy slopes. Travel hazards abound at lower and middle elevations due to historically low snow with the incoming heat wave rapidly erasing the recent snowpack gains.

Are you heading out?  Let us know what you see by submitting an observation here or on the AvyApp.

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