Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Winds will redistribute recent snow to form shallow slabs you can easily trigger. Older stubborn large slabs may retain more reactivity at upper elevations and you could trigger them farther down on the slope. Treat lee slopes near ridgelines with suspicion and give wind loaded alpine start zones a margin for safety.

Avalanche problems

  • Wind Slabs

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

    At all elevations, W winds picking up Thursday night may transport snow through the morning hours on Friday. There is plenty of low density snow to transport. This process makes the transported snow dense and slab-like compared to the unconsolidated snow it sits on top of.  If you find active blowing snow or fresh, sharp wind lips, start paying attention to the degree of potential deposition. Test these surface deposits for reactivity and steer around steep slopes with active deposition or where lens-shaped deposits have formed below ridgelines.

    A relatively calm day on Thursday gave Wendesday's slabs more time to heal, but an explosive triggered avalanche with a 2 ft crown in A-zone suggests that these large slabs still have some legs left. By Thursday, they might retain reactivity in isolated locations such as unsupported, heavily wind-loaded features at upper elevations. If you head into committing terrain up high, use a small test slope to evaluate firm, cohesive snow over less consolidated layers. You may have to dig down a foot or two to find them. It is possible that these slabs have lost reactivity.

    The best and safest riding conditions can be found in wind sheltered terrain. Here, you might still be able to get a small dry/moist loose avalanche running in steep terrain, so consider what terrain you could get pushed into if one were to knock you off your feet.

Avalanche Discussion

4-6" of snow low-density snow has accumulated nearly every day this week, but the snowfall mostly tapered off after 6 AM on Thursday. Accumlations are in the 2 ft range at ski area bases since Valentine's Day. There have been 3 rounds of wind slab formation since 2/15. The most recent wind event on Wednesday formed above a layer of less wind affected snow, potentially prolonging its life. The same possibility may occur again on Friday. And both wind slabs could be in play in similar terrain as these slabs are forming on typical aspects with W winds.

Below the patchwork of wind slabs, you'll likely encounter a thin 2/16 rain crust at lower elevations. An observer at the upper elevations of Ski Bowl (~5000 ft) noted a poor bond to the crust, so it is worth monitoring this interface as snow continues to accumulate and gradually settle into a slab. Ascending into middle elevations, the 2/16 rain crust dissipates and your next crust is likely to be the 2/13 or 2/7 rain crust.

On Wednesday, Mt Hood Climbing Rangers encountered touchy, subtle soft slabs at middle elevations and firmer slabs at upper elevations, initiating slabs up to size 1. In both cases, the slab reactivity could be partially attributed to the layer of less wind affected snow from Tuesday. You can read the observation here. The same day, in more sheltered terrain around Vista Ridge, observers were able to initiate cracking and suggested that low-density snow totals on Wednesday might be more in the 4-5" range than the 2-4" range that appears on the weather stations. In the Mt Hood Meadows area, winds were pushing into more exposed terrain around the Canyon where Mt Hood Meadows Pro Patrol initiated isolated 8-10" slabs. By Thursday, Patrol only initiated shallow dry loose avalanches within the fresh 4-6" of surface snow in this same terrain. There was minimal wind loading.

Avalanche professionals across the region continue to find weak layers in the upper 1-3 ft of the snowpack from our recent high pressure. As our snowpack becomes increasingly layered, it will be important to take note of any critical observations. Over the last several days we haven't had any reported instabilities involving these older interfaces, but isolated pockets of surface hoar could lurk and a layer of preserved stellars was reactive in some areas over the Presidents' Day weekend. Please let us know if you find any of these layers.

We could use the observations as winter finally makes a return. Let us know what you see by submitting an observation here or on the AvyApp.

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