Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Continued warm temperatures mean you can trigger wet snow avalanches on very steep slopes below roughly 7000 feet. These could injure or burry you if they carry you into a terrain trap, like a gully, dense brush, trees or rocks. Move off of - and out from under - steep slopes if you trigger, or notice, recent roller balls and pinwheels.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    You can trigger sluffs of dense, wet snow on slopes steeper than about 38 degrees. These can be dangerous on slopes above terrain traps and will run farther slopes without low-angle benches that can slow moving debris. Rollerballs that fan out from your machine or boards are a clear sign that the surface snow is wet. Step back to lower-angled terrain if you see these conditions. This hazard may be more widespread on shaded slopes where the surface snow is getting wet for the first time. 

    Natural roller balls were running in steep treed or rocky terrain below 6000'.

Avalanche Discussion

We’re on a hot streak. Or a warm streak at least. The temperature at Noisy Basin in the Swan Range hasn’t dropped below freezing since Monday, December 18th at 0700. Temperatures will remain mild until late today, making it a full work week of warm. Most mid-elevation weather stations have faired similarly. Meanwhile, temperatures at upper elevations have hovered just below freezing this week.

With extended mild temperatures at middle elevations, it’s likely that many steep slopes in this elevation band have already been worked over by rollerball or loose wet activity. Shaded aspects and upper elevations, however, still harbor dry snow that is transitioning to wet and will be ripe for sluffing. If you climb above 7000 feet in your search for dry snow, recall that these highest reaches of the advisory area are where buried weak layers are most likely to have survived previous warm-ups. Dig down and verify that there is a stout 12/7 crust capping early-season snow. In its absence, dig a little deeper to identify any buried weak layers, like the 12/1 surface hoar. This weak layer is identifiable by a grey stripe in the wall of a snowpit. If you find this poor snowpack structure (i.e. thin breakable crust and a layer of buried surface hoar), move to a different slope or aspect. Thankfully, this poor structure is proving hard to find.

Fortunately, warm temperatures will clock out for the weekend as a cold front arrives this evening. This system will deliver 2 to 5 inches of snow and enough wind to blow it around. If you’re the nocturnal type you might encounter some new snow problems, otherwise the incoming precipitation shouldn’t be a factor during today’s travel.

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