Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Points saillants

The conditions for wet avalanches may develop on certain aspects and elevations on Friday, and it will be your job to notice the clues that indicate conditions are ripe. Remain alert for a poor overnight refreeze and areas where you sink into wet, mushy snow past your ankle. These conditions, especially on shaded aspects, are more likely to produce generally small wet avalanches. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1–1.5

    Small wet loose avalanche activity could develop in isolated areas once again on Friday. Expect a poor overnight refreeze thanks to increasing cloud cover. Once thin surface crusts break down, the resulting wet, mushy snow conditions are areas where an isolated natural or human triggered wet avalanche might occur. Thanks to a week of above-freezing temperatures on Mt Hood, we expect the majority of wet avalanche activity has already run its course, but wet avalanche activity might redevelop during periods of strong sunshine or if a band of rain showers moves through, destabilizing the surface snow. Note signs of fresh avalanche activity, wet or sloppy snow you can sink into past your ankle, or rollerballs. If you observe any of these, transition to shaded aspects or out from under steep slopes where a wet avalanche could entrain enough surface snow to get you into trouble. 

    Example: Small wet loose avalanches. These could occur on slopes in the sunshine or if wet snow conditions push onto shaded aspects.

    Photo: Joe Dellaporta

Avalanche Discussion

Snow surface conditions are likely to hang in the balance on Friday, thanks to a tricky cloud forecast, a chance for isolated rain (and highest elevation snow showers) late in the day, continued mild temperatures, and light SE winds. We're not sure how much refreeze you will experience in your terrain due to overnight cooling. If more cloud cover exists on Thursday night, expect a worse overnight surface refreeze. But the cloud cover continues to increase during the day on Friday, so it is also possible that many aspects may remain frozen or that thin, breakable crusts will persist much of the day. Given the variety of snow conditions you might encounter, Friday is less likely to follow the typical melt-freeze playbook than recent days. Nevertheless, we expect that firm surfaces may be your primary hazard on some portions of the mountain, particularly early in the day.

It has been a very mild start to April. Since April 3rd, freezing levels have been flirting with the summit of Mt. Hood at nearly 10-11,000 ft. Since that date, the snow depth at Mt Hood Meadows has decreased by nearly 1 ft due to consolidation and melting. The first warm days came as a shock to the dry, upper snowpack, with easily triggered wet loose and even a couple of naturals reported. As high freezing levels persisted, natural wet loose mainly ran their course, while human-triggered wet loose could still be pushed in very steep terrain. On Monday, the Mt. Hood Climbing Rangers reported deeper water percolation and more stubborn wet loose than on previous days. They also found a supportable crust capping dry snow at higher elevations that broke down with daytime warming (observation here).

Thankfully, winds on Tuesday and Wednesday, along with clear skies overnight, allowed snow surfaces to refreeze, especially in more wind-exposed terrain despite mild temperatures. A solid overnight refreeze was reported on Wednesday night, thanks to clear skies. During the day on Thursday, areas experiencing strong April sunshine saw the 3/31 crust break down, aided by minimal wind and temperatures rising into the 40s and 50s. A few small human-triggered wet avalanches were reported on S and SE aspects during the afternoon hours on Thursday, suggesting that in some areas the upper snowpack is still adjusting to the heat. This activity was isolated. At NWAC upper elevations on the south side of Mt. Hood, riders reported excellent melt-freeze riding conditions, with ankle-deep boot penetration by 11 AM. Riders ascending above NWAC forecast elevations found firm, frozen surfaces in the morning hours.

It's that time of year when you should keep other mountain hazards on your radar. Expect mornings to be firm with long, sliding falls being your primary concern. Pack the appropriate traction and self-arrest tools for your objective. Also, consider rock or icefall as the day heats up. The Mt. Hood Climbing Ranger page is a great resource for upper mountain planning. 

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

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