Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Dangerous avalanche conditions will continue on Friday.  You can trigger a wind slab avalanche on steep wind-loaded terrain at any elevation, with deeper and more consequential slides likely at mid and upper elevations.  Mitigiate the threat of very large avalanches releasing from the upper mountain by limiting your exposure to canyon runouts even near forested terrain. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    While snowfall rates will back off compared to earlier in the week, strong winds at mid/upper elevations and extreme winds in the alpine will continue to load the same lee slopes that have been pounded for several days.  We are firmly in the window (see photo or discussion) where a very large and unsurvivable avalanche can release from up high.  Don't become complacent. You need to give yourself an extra margin of safety and limit your exposure to canyon runouts even at lower elevations.  

    It shouldn't be a struggle to find wind-affected snow at all elevations on Friday with strong W-SW winds showing no signs of backing down.  Continue to avoid steep wind loaded slopes where you could trigger a large wind slab avalanche or a small avalanche in a terrain trap like steep trees or in a gully where you could be more easily buried. 

    Look for clues like blowing snow, textured snow surfaces and fresh cornices to help you discern which slopes have been recently loaded.  Red flags like shooting cracks in wind-drifted snow are signs you'll likely trigger an avalanche on nearby steep slopes.  Avalanches may break within storm layers or to older crusts (now several feet down) and run far distances at mid and upper elevations.   To enjoy the new snow safely, choose simpler, less wind-affected terrain without overhead hazard. 

    (2/29/2024)

    Deep debris from another huge avalanche (est D4) in Clark Canyon. The avalanche originated in Heather Canyon and ran several thousand feet to lower elevations on Thursday morning. Due to storm conditions and poor visibility, it's unknown whether or not the avalanche was a natural avalanche or caused by artillery during avalanche mitigation. 

    Photo: Dave Watson - MHMSP

Avalanche Discussion

We've received over 5" of water since Sunday with several feet of new snow accumulating at mid and upper elevations and periods of rain mixing in at lower elevations.  Average winds speeds since this storm cycle started have averaged 25-30mph out of the SW or WSW with much higher gusts.   We're in a much cooler and showery pattern for the short term, and we can expect showers to bring low density snow and graupel along with continued moderate to strong winds. 

Visibility has been limited but on both Wednesday AND Thursday, MHM pro-patrol found debris from very large avalanches in Clark Canyon that likely released Tuesday night and again on Wednesday morning from Heather Canyon.  It's unknown whether or not one or both slides occurred during avalanche mitigation. The debris from both slides is now as deep as 50' (!) in some places.  It's a stark reminder of the massive avalanches that can happen on Mt Hood during or following a multi-day storm cycle and often during periods of poor visibility.  Professionals over at Pea Gravel ridge found strong winds and wind affected snow, touchy wind slabs on test slopes, and new cornices as soon as they pushed near treeline.   All of the new snow has not settled and deep snow immersion/tree wells are a real concern.  Ride with a partner and keep one another within sight. 

All of the storm snow rests on the 2/24 interface.  Going deeper in the snowpack, a series of crusts and pockets of weak snow existed above the stout Early February Crust (EFC). These layers produced inconsistent snowpack test results and showed signs of gaining strength before this storm cycle and are now buried several feet deep.  

Régions couvertes