Bollettino valanghe

Mt Hood

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Thu
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
Open full map
Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very dangerous conditions remain at upper elevations due to continued snowfall and strong winds.   Upper elevation natural avalanche potential creates risk for large avalanche runouts, particularly as the storm intensifies during the afternoon.  Below 3000 ft, warming snow may produce natural loose wet avalanches or roofalanches. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    Mt. Hood won't get the break it needs for wind slabs to strengthen as back-to-back storms bring moderate snowfall and strong winds reload lee slopes. As the incoming storm ramps up, natural avalanches remain very likely at upper elevations. Every day without a real break increases our uncertainty at upper elevations where natural very large avalanches (D3 or larger) may run from upper elevations down to valley flats well below treeline. Near treeline travel will be dangerous, but can be managed by diligently avoiding lee slopes steeper than 35 degrees and large avalanche paths / runouts.  Visibility and ground blizzard potential will create challenging route-finding and travel conditions near and above treeline.

    Example: Easily triggered wind slab in the lee of a ridgeline. Slabs such as this will range greatly in size and depend on the scale of the feature on Wednesday.

    Photo: Matt Lubar- Baker Mtn Guides

  • Storm Slabs

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

    Snowfall rates will increase throughout the day on Wednesday.  Pay attention to the changing character of the storm slab. Warming temperatures and increasing snowfall rates may make slabs increasingly touchy during the afternoon even if slabs start the day less reactive. Simple shovel shear tests can help you identify layers of concern in the upper snowpack. Look for signs of instability like cracking in the new snow and recent avalanches as an indicator to stay off of similar slopes. Choose supported slopes less than 35 degrees as the storm intensifies. 

    (1/4/2022)

    Example from the West South zone: Simple tests can help you identify potential points of failure in the recent storm snow. Be sure you take a hard look at all of the snow above the 1/2 interface before stepping into consequential terrain. There were plenty of points of failure found on 1/4 at White Pass.

    Photo: Dallas Glass

Avalanche Discussion

Remember that very large avalanches can release from the upper mountain and run thousands of feet down the main canyons during or after multi-day storm cycles. Keep this on your mind when choosing where to travel even at lower elevations, and don't be lulled into complacency during short lulls in the action.  A very large natural avalanche occurred on 12/23 on the Newton Clark Headwall. Find out more information in this REPORT in the NWAC Avalanche Occurrence Database.  It's a great reminder of the higher uncertainty surrounding deeper layers in the alpine snowpack. 

Over the next 36-48 hours, the last hurrah in a lengthy storm cycle will bring a warming trend and a changeover to rain. At most elevations, this changeover to rain will hold off until after dark on Wednesday; but ultimately the warm air will win out, creating the potential for widespread very dangerous avalanche conditions Wednesday night.  Below 3000 ft, a changeover to rain during daylight hours may produce roofalanches that can be large or even fatal - so don't linger around the sides of a snow-loaded house or shed. The warm-up can also produce wet loose avalanches on steep slopes approaching 40 degrees. 

Mt. Hood remains in the midst of a massive storm cycle that has dropped 3 ft since 01/02. Ski area closures and access challenges continued on Tuesday. NWAC forecaster Andrew Kiefer traveled the Mitchell Creek area where he found variable snowfall rates and poor visibility. Given 1" per hour snowfall rates, the below treeline snowpack was healing faster than expected. Multiple planar interfaces did not propagate in snowpack tests. The solstice crust is down approximately 7 ft and remains a slight concern as a failure plane for very large upper-elevation avalanches.

Monday was an even wilder day on Mt Hood and the surrounding area with heavy snow down low and whiteout conditions/strong winds. Mt Hood Meadows Patrol had the upper mountain/lifts closed and on the lower mountain reported widespread touchy storm slab avalanches during avalanche mitigation.  The avalanches broke within the new storm snow and were sometimes triggered while approaching steeper terrain.  Despite the extensive and ongoing wind transport, at least below treeline, the slabs were soft and had not yet become denser wind slabs.  There were no observations from the upper mountain. 

Prior to this system,  very enjoyable and plentiful cold low density snow could be found on much of the mountain.  An active storm track over the next several days will likely keep the avalanche danger elevated.  

Regioni coperte