Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

The threat of very large and destructive avalanche from the upper mountain peaks Thursday night into early Friday. Don't expose yourself to large avalanche paths originating from the upper mountain until the storm relents.  Storm snow needs more time to settle and can be triggered on or above slopes 35 degrees and steeper.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3.5

    Thursday night will be one of the most intense periods of a massive storm cylce at Mt Hood. As the cycle continues unabated, the potential for even large slabs (up to size 3.5) exists. The likelihood of natural avalanche activity peaks Thursday night into early Friday, then decreases slightly as snowfall and windspeeds ease slightly. This is one of those scenarios when the combination of sustained high winds, heavy snowfall, and a complete lack of observations from the upper mountain outside of weather station data makes us nervous about very large and destructive avalanches releasing from the alpine and running several thousand feet downslope.  Let the ongoing storm cycle run its course and stay out of the canyon runouts at lower and mid-elevations. 

    Winds continue to hammer Mt Hood, transporting snow at all elevations.  Firmer, harder wind slabs have likely formed well below typical start zones, loading the terrain in erratic patterns.  These wind slabs may be harder to trigger but if they release,  a large and consequential avalanche is almost guaranteed. The best advice is simple, stay off of large open steep slopes capable of producing large avalanches.  Visibility is likely to prevent you from using visual cues that would normally help keep you out of trouble in potentially wind-loaded terrain.

    (1/6/2024)

    Hard slab debris from a human triggered avalanche on Pea Gravel Ridge. 

    Photo: Jack Kuenzle

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    We're expecting storm slabs to release within the upper 1-3 ft of storm snow. Snowfall rates have been in the 1-3 inch per hour range and this snow needs to settle a bit before it stabilizes. When in less wind-exposed terrain, seek terrain less than 35 degrees for another day. It's not the day to push your luck on a larger steep slope, or a slope that rolls away beneath you into a terrain trap. Use small steep test slopes to look for signs of instability. Cracking, collapsing, and recent natural avalanches all confirm the problem.

     

Avalanche Discussion

You'll need to wrestle with lingering uncertainty surrounding deeper weaker layers that were reactive before this storm cycle started.  That crust is now 4-5 ft down in the snowpack. These avalanches are increasingly hard for humans to trigger except in shallower areas, but these deeper layers could be tipped over the threshold by active wind loading. Areas of concern include shallower snowpacks to the east of Mt Hood and upper elevations where crusts may not extend. Keep in mind that as recently as last weekend, remotely triggered avalanches and rumbling whumpfs occurred on NW-N-E aspects above 5500'. 

We're up over 10" inches of water/6 ft of snow since January 6th!  This snow has transformed the landscape, especially the snow-starved lower and mid-elevations in less than a week.  Avalanche professionals in the Vista Ridge area found a new melt-freeze crust (1/8) down 1.5 ft. Older crusts 1/4 and 12/30 did not produce propagating test results.  It's important to note, that the snow-line took a detour up to 6000-6500' on Monday, forming a mid-storm cycle crust at lower and mid-elevations.  

On Tuesday, Mt Hood Meadows patrol encountered touchy storm slabs up to 3' deep that were easy to trigger below treeline on N-NE-E aspects.  The slabs broke within the recent snow that's accumulated since the cool-down Monday night.  Extreme winds and storm fluctuations had formed a boot-supportable crust above treeline.  Winds and snowfall limited visibility into the surrounding terrain. 

Travelers last weekend remotely triggered avalanches up to size D2.5 and other groups reported whumpfs. Two prominent potential weak layers exist in the upper snowpack that are suspected in these events. The 1/4 and 12/30 crusts both have potential weak snow above them. If avalanches fail on these layers, they could wrap terrain features. 

As snow totals add up quickly, deep snow immersion is becoming a real concern.  Travel with a partner and beware of falling into tree-wells and open creeks!

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