Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

Triggering a large destructive avalanche on a buried weak layer remains possible. Warm temperatures will keep the threat of wet slides at all elevations. Variable surface conditions could make travel difficult. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Weak layers buried 2-4+ feet lurk in our snowpack. Although we have had less recent reports of direct-action avalanches, the seriousness of triggering a hard slab slide keeps this problem listed. At this time, we are unclear on the distribution of the weak layers, and all slopes should be suspect until proven otherwise. 

    Use conservative terrain management. You may or may not get cracking or collapsing before triggering an avalanche. These slides may be triggered remotely, from gentler terrain below, above, or to the sides of steep slopes. Persistent Slab avalanches can break wider and higher on the slopes than expected. The only way to identify this problem is to dig into the snow. Look for angular “sugar” snow resting above or below a crust formed in late December. On steep cut banks and road cuts below 5500 feet, depth hoar (sugar snow) may exist on isolated, open, unvegetated slopes. These slopes may break near the ground, taking the entire snowpack with the slide.

     

    (1/19/2024) January 19th, 2024: Looking across and down the slope at the debris from the avalanche in Shed 9.

  • Loose Wet

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

    Today’s warming temperature may cause natural wet loose slides at all elevations. The recent rapid temperature change increases the threat of natural and triggered avalanches. Slides can entrain substantial amounts of loose surface snow.

    Rollerballs, trees shedding snow, and observing the surface of the snow turning moist are all precursors to a wet loose problem. Keep an eye out for slopes that are warming for the first time since Wednesday’s storm. Stick to lower-angle slopes without overhead hazards to increase your safety.

    (1/20/2024)

    Rollerballs were observed in the moist surface snow on Saturday in Kimmerly Basin. These are precursors to a wet loose slide.

Avalanche Discussion

Thursday's bitterly cold temperatures preserved Wednesday's 1-2 feet of low-density snow. Unfortunately, temperatures at mid and upper elevations began rising Friday and continued overnight. Saturday, all mid-elevation and a couple of upper-elevation stations climbed above freezing, while valley cold pools limited temperatures to the mid-20s. A freezing rain crust was noted in Essex and Ferndale on Saturday morning, with mixed precipitation continuing through the day. This morning (Sunday), temperatures remain mild at mid and upper-elevation locations, with Noisy Basin above freezing since 0500 Saturday. The valley's cold pool may get mixed out, with temperatures potentially climbing above freezing which would end the freezing rain concerns.

Today (Sunday), expect to find a thin, breakable crust on many surfaces above the valley cold pool, which may be capped with a thin layer of fresh snow. This crust could break down as temperatures warm through the day. Beneath the crust, there remains 1-2 feet of dry snow, which was the cause of yesterday's difficult travel and excessive skin glopping. Natural wet loose activity should be limited to locations where the surface stayed dry. However, with last night's weak freeze, the possibility of a rider-triggered slide remains at all locations. If so, we expect to see rollerballs and wet loose activity on steep slopes at low elevations, such as cutbanks or road cuts.  

A party in the Skyland area experienced multiple audible collapses in sheltered and wind-affected terrain with shooting cracks. The snowpack in this area is thin and possibly the weakest of any location in the Flathead. Below the warm air, several parties noted substantial cracking and collapsing in areas harboring cold, dry snow capped by a freezing rain crust. 

Despite increasing winds today, we have removed wind slab from the problem list. We assume the moist, wet, or frozen surface snow is limiting transport. If you do reach the upper elevations, keep an eye out for thin slabs on typical leeward aspects. 

Observations from Saturday were not inspiring. FAC visited Marion Lake in the Essex area, where we encountered six experienced groups who lamented how bad the riding was. Most turned around early to limit to limit their exposure to injury. Nearby, a veteran observer mentioned that this snow was some of the worst glopping skinning he had ever experienced. Another seasoned user's take-home message from his Essex tour was that the climb and descent were very difficult and the skiing was horrendous.  Four observations from the southern Whitefish Range mentioned warm, moist, and heavy surface snow (Observation 1, Ob 2, Ob 3, Ob 4). Observations like these make you want to stay home and cheer on the Buffalo Bills this afternoon.

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