Bollettino valanghe

Seeley Lake

West Central Montana Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow over the weekend has built back our lost base and is bonding well. New snow and wind today will form fresh wind slabs at upper elevations. These will grow in size and touchiness throughout the day. Avoid wind-loaded slopes greater than 32º.

Problemi valanghivi

  • Wind Slabs

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

    Throughout the day, fresh wind slabs will build. Winds are mostly light, with strong gusts. However, stronger sustained winds are likely at ridgeline. Fresh snowfall today plus low-density snow on the ground means abundant snow is available for transport. Upper elevation slopes, just below ridgelines, are the most likely places to find wind slab. Cross loading is possible as well. Be cautious of steep gully walls. The touchiness of slabs will increase throughout the day and with it the likelihood of triggering wind slab. Avoid slopes greater than 32º. Fat, wide pillows below ridges, and wind lips are indications of wind transport. Avoid these features as you travel today.

     

Avalanche Discussion

The weather has been pretty good to this region over the past few days. We’ve had a total rebuild of the base lost during the warm spell, plus more. Snow totals in the past 72 hours are roughly:

  • 10 inches in the Missions
  • 22 inches in the Rattlesnake
  • 27 inches at Lolo Pass
  • 22 inches in the central Bitterroot
  • 14 inches in the southern Bitterroot

Yesterday, Mt. Fuji at Lolo Pass had 44 inches of snowpack, almost all of it fallen in the past week. Point 6 had between 31 and 35 inches. The snowpack was mostly unconsolidated, right side up, and almost void of layers in both places. There were no concerning test results. The new snow was readily sluffing on steep convex rolls and road cuts.

Below about 7000 feet, the new snow fell on 12 inches of low-density snow and bonded well. Above 7000 feet, old snow left after the 11/26-12/4 thaw forms a base of melt-freeze crusts up to 20 inches thick. Bonding seems to be good at this interface as well.

Early season hazards are still very much in play despite the depth we now have. The lightness of the snow means there is little buffer on top of rocks and stumps. Care is still warranted to avoid injury from unexpected contact.

At upper elevations and below ridgelines, wind slab formed during the storm. However, this was mostly unreactive yesterday. There were likely pockets of more reactive wind slab out there; we just didn’t find them. Mild temperatures and a uniform snowpack are good for bonding, but avoiding steep wind-loaded slopes is wise. 

There is more snow and wind in the forecast today. Up to 7 inches of snow are expected, although more is possible. The wind is westerly and mostly light to moderate. Strong gusts will aid snow transport. Wind slab will build throughout the day on easterly faces. 

Human triggered avalanches are possible today. Dial it back to slopes less than about 32º as the day progresses, and wind slabs build. Loose snow avalanches are likely today. While manageable, gullies, terrain traps, and early season hazards increase the consequences of being knocked off your feet and carried by these.

Please send us your observations if you get out in the field. It benefits not only the forecast but other backcountry users as well. You can submit them here: https://missoulaavalanche.org/submit-an-observation/

Ski and ride safe.

Regioni coperte