Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sun
Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

It’s unlikely that you’ll trigger an avalanche today. It’s not impossible. Want to ride steep, wintry snow on shady, sheltered terrain? Choose planar or concave slopes with clean runouts, and avoid convexities. If you’re looking for corn snow on sunny slopes, look for rollerballs around rocks as a sign that you’ve overstayed your welcome.

Problemi valanghivi

  • Persistent Slabs

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

    I will assess shaded and sheltered slopes without a firm, supportable surface carefully. I'll probably still avoid steep rocky areas, convexities, and complex terrain with soft snow. That's because, on some of those terrain features, you could trigger an avalanche that breaks on buried weak layers. Spotty surface hoar in the southern Whitefish Range and facets in the Flathead Range - where they exist - are the primary layers of concern. While these layers are found across the forecast region, the instability is isolated. The last reported avalanches breaking on these layers ran on the 7th. You can still ride steep dry snow while avoiding the problem. Stick to planar or concave slopes with clean runouts - no gullies, trees, or rocks below.

    (2/11/2022)

    Riders spotted this large Persistent Slab avalanche from earlier in the season.

    Photo: Pete Costain

Avalanche Discussion

Weather stations around 6000 feet showed high temperatures above freezing Friday, with some stations below 5000 feet reaching the 40s. Plenty of sunshine softened the recent melt-freeze crust to almost corn on south aspects in the Whitefish Range. Despite the sun and above-normal temps, observers elsewhere mention that the 1-2 inch thick crust stayed crusty. Frozen rollerballs and wet loose debris from Thursday's balmy warmup made travel challenging. It will be another warm and sunny day. Solar aspects have already been through the melt-freeze cycle. We might have good corn skiing. But if you see rollerballs coming down from rocks as the snow surface thaws, dial back slope angles and avoid confined chutes with wet snow.

The crust goes into the alpine on solar aspects and up to about 6000 feet on north- and east-facing slopes. On those shady slopes, dry winter snow is settling in sheltered terrain. Exposed terrain is wind-affected. Strong winds earlier in the week left old, hard slabs below leeward ridgelines. Well-developed cornices hang over some typically leeward slopes. I'd give them a wide berth as the sun beats down on their precarious roots.

Surface hoar and facets buried six to 18 inches have been gaining strength. The last time snowfall stressed those layers was the 4th. The last time winds built slabs above them was the 7th. The last reported avalanche that failed on buried surface hoar was on the 7th east of Whitefish Mountain Resort. Very large avalanches, which also ran on the 7th, likely failed on weak facets. Days of warm weather and freezes overnight have likely shrunk the distribution of the problem. The holdouts are steep, complex, convex, northerly slopes without the recent melt-freeze crust or supportable wind-scoured snow. Those are the isolated features where I will still think twice before committing.

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