Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Widespread wind slabs are gradually becoming less reactive due to warming temperatures, but you could still trigger one.  Identify and avoid wind-loaded slopes steeper than 35 degrees,  particularly above treeline. With warm temperatures and sunshine in the forecast, avoid aspects where wet snow  and roller ball activity may lead to loose wet avalanches.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    A recent storm brought 6-14" of snow to the Mt. Hood area with moderate winds from Tuesday through Wednesdsay evening building reactive wind slabs. These slabs are larger and more widespread as you ascend. With relenting weather on Thursday and milder temperatures, wind slabs are still large and dangerous, but are becoming stubborn to trigger.  This means that you are most likely to trigger one on terrain approaching 40 degrees that are heavily wind-loaded. Descend from ridge-tops cautiously, observing signs of wind-loading such as chalky or pillowy-textured snow. When in doubt, choose wind-scoured or lower-angle terrain and navigate away from features such as cornices and convex rolls.

Avalanche Discussion

Under the influence of a ridge of high pressure, the freezing levels will rise above 10,000 ft on Friday, with mostly sunny skies through early afternoon before clouds increase.

Warm temperatures mean that you can expect isolated loose wet avalanches where direct (but weak) November sunshine softens recent unconsolidated snowfall (primarily below treeline). Look for signs of of roller ball activity or wet snow that you can sink in deeper than your ankle. If you encounter these conditions, adjust your aspect to find cold snow surfaces. Keep in mind that while Thanksgiving day brought above-freezing temperatures up to 6500 ft at Mt. Hood Meadows, and this may have triggered some loose wet activity, Friday will be warmer, so wet snow will be more prevalent. Despite the great start to our winter snowpack, keep early season conditions in mind. Rocks, stumps, and vegetation may be barely covered and many creeks are open. Remember that even a small loose wet avalanche can cause significant trauma around shallowly submerged terrain obstacles.

With 45-50" of snow depth at mid elevation, the Mt Hood snowpack is far above average for this time of year.  After our initial snowfall, a rain event and warm period built a supportable rain crust on November 16th. This has served to lock in the base of the snowpack and batter down vegetation creating surprisingly good travel conditions and snow coverage for November.  Snow that fell last week is generally well bonded to the 11/16 rain crust and no significant avalanche activity was observed in the recent snow.  Friday and Saturday (11/20-21) brought sunny, calm, and warm conditions. The snow surface stabilized as a crust formed on solar aspects and lower elevations. Higher elevation and shaded slopes largely escaped the melt cycle and good travel conditions were found on these slopes throughout the weekend. The recent 6-14" of snow and wind slabs sit on top of these crusts and higher elevation old snow surfaces. 

Now is a great time to run through your safety equipment and make sure everything is in good working order. CLICK HERE for more information on early-season equipment checks. What did you see out in the field? SHARE YOUR OBSERVATIONS with NWAC and the backcountry community. Check out this BLOG POST and VIDEO TUTORIAL to find out more about why observations are so important and how you can view and share information on NWAC’s new public observations platform.

The Covid19 pandemic continues to be a major health and safety concern. Avoid unnecessary risks that could result in a rescue or stress medical resources. Follow local and state guidelines and wear a mask when appropriate. Maintain social distance and recreate responsibly and closer to home. 

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