Bollettino valanghe

Mt Hood

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

Shifting and powerful winds will form dangerous slabs you are likely to trigger on a variety of aspects. Avoid slopes steeper than 35 degrees in wind-affected terrain. At lower elevations, navigate away from steep slopes if you encounter sticky, wet snow.

 

Problemi valanghivi

  • Loose Wet

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

    Very shallow wind slabs built Monday and Tuesday, but the majority of the danger arrived with warm front Wednesday afternoon. Dry snow below treeline will become wet or saturated Wednesday night into Thursday as temperatures warm up. We expect there's only about 6" of dry snow above the late December crust, but this snow will destabilize quickly the moment snow changes to rain, triggering a round of shallow rollerballs and loose avalanches on slopes steeper than 35 degrees. Once the warm-up has occurred, you can still trigger a shallow avalanche if you find saturated snow deeper than your ankle. 

    Example: This natural wet loose avalanche occured as snow shed from rocky complex terrain.

    Photo: Public Observation

  • Wind Slabs

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

    Snowfall Monday night (2"), Tuesday night (4") and late Wednesday (3" and counting) has drastically improved riding conditions. However, strong E winds on Wednesday formed sensitive slabs on W aspects near and above treeline.  Under poor visibility conditions, backcountry travelers triggered a large 12-14" hard slab from below, with significant propagation up the slope. Snow continues to arrive in pulses through Thursday while steady moderate to strong winds will continue to transport that snow - at first onto W aspects, and then increasingly onto northerly aspects on Thursday.  Mt Hood Meadows Pro Patrol found reactive 4-6" wind slabs on Wednesday running far on a slick late-December crust. We're not sure how long it will take to form a better crust with the crust, but mid-storm interfaces may also prove reactive. Any of these avalanches could be large and 2 ft deep by Thursday. Sustained and shifting winds aren't the only problem: milder temperatures on Thursday could also give these slabs some characteristics of wind-loaded storm slabs, making it significantly harder to avoid the problem by heading onto windward slopes. Monitor slabs on all aspects for reactivity and depth. Punchy snow layers, reactive interfaces, shooting cracks, or whumphs all serve as reminders to stick to lower angle, wind-sheltered slopes or safer travel along ridgelines on Thursday. Large, overhung cornices and active wind transport continue to highlight areas where the danger will be greatest.

    If snow levels are lower than forecast through Thursday, wind slabs may remain or even grow in exposed below-treeline locations. Constantly evaluate the depth of the snow over the crust as you travel.

Avalanche Discussion

As new snow continues to trickle in - it will be important to track what this new snow is falling on. Some folks have been finding surface hoar living in specific areas, such as sheltered areas from the wind with minimal canopy.  On Tuesday Joe Dellaporta observed weak faceted snow above and below the 12/30 rain crust on a NE aspect at 6000 ft.  This could contribute to more widely propagating avalanches, making it essential that you listen for whumphs or collapses as you travel.

Thanks for all the recent observations! Avalanche forecasting is a community project, so having recent observations from the public is a huge part of the process and helps make for a better forecast.  Keep them coming!

Regioni coperte