Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

You can trigger an avalanche large enough to bury you on shady slopes. Warm temperatures overnight and today may increase the chance of wet snow avalanches. If you are sinking into mushy snow, choose lower-angled terrain to reduce your risk. 

This is the last daily forecast of the season. We will issue snowpack updates Monday, Wednesday, and Friday through April 28. Thank you for supporting the FAC.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Yesterday, a skier unintentionally triggered a Persistent Slab avalanche on a northerly aspect of the Flathead Range (photo above/to the right). Today, It remains possible that you could trigger a 1-2 foot thick avalanche on a layer of weak snow buried beneath last weekend's storm snow. This layer is thickest and best preserved on shady aspects at mid and upper elevations. Since last Sunday's rash of slides, yesterday's was the first reported avalanche on this layer. Over the last few days, we have mentioned that warming temperatures may consolidate the surface snow into a slab in previously unconsolidated areas. This may have played a role in yesterday's incident.

    Warning signs such as collapsing or whumphing was noted by a group Friday but are becoming less common. The chance of remotely triggering one of these slides has decreased substantially. You may not receive a warning sign until the slope you are on avalanches. This problem is near the surface and can be found by digging beneath last weekend's snow and testing this layer. Default to lower-angle terrain for a safer experience.

     

     

    (4/8/2023)

    The crown of an unintentionally triggered Persistent Slab avalanche. The skier was able to ski out of the slide safely.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Today will repeat the past few days as balmy daytime temperatures develop wet snow instabilities. The natural activity is mostly over on slopes that have received substantial warming. However, overnight temperatures around freezing result in a thin surface crust that will break down and allow riders to trigger a slide in the mushy surface snow. In terrain that has not experienced significant warming, today's temperatures might moisten the snow surface and initiate natural avalanches. 

    With the highest temperatures of the season expected today, we anticipate Wet Loose avalanche problems to develop earlier in the day and become more widespread. Resulting slides may travel far on the underlying crust on solar aspects. Surface slides on shady slopes could trigger a larger avalanche on a buried weak layer. Upper-elevation locations exposed to south-southwest winds may remain frozen. 

    Surfaces warming for the first time will develop rollerballs or pinwheels, precursors to a wet slide. Choose lower-angle slopes where you or your machine sink more than a few inches into the surface mush—limit time spent in long-running gullies or above terrain traps where the snow can pile up deep. 

    (4/4/2023)

    Skier trigger roller balls on sunny slopes. Surface snow was getting moist by early afternoon.

    Photo: sw

Avalanche Discussion

Following an unusually cool winter and early spring, temperatures have felt balmy over the past few days. Today will be the fourth day of above-average temperatures and the third night of a poor refreeze. Yesterday, all mid-elevation stations reached the upper 30s to low 40s F, with the Tunnel Ridge snow (5895') topping out at a whopping 48F. Several upper elevation stations climbed above freezing, with Tunnel Ridge wind (6796') hitting 38F. As of 0400 this morning, temperatures remain at or above freezing at many mid-elevation stations with upper elevations at mid to upper 20sF. Today will be partly cloudy, with temperatures five or more degrees warmer than experienced over the past few days.

Temperatures tonight and Monday will be well above average and the warmest of the season. Rain associated with incoming Pacific moisture may occur at the upper elevations. We expect dangerous avalanche conditions to develop with wet snow instabilities on all aspects and elevations. Meltwater percolating into the snowpack may reach a near-surface weak layer and result in wet slab avalanches. 

Warm weather increases the potential for cornice fall and glide avalanches. Forecasting for either of these is difficult and imprecise, and we recommend safe travel protocols to limit getting tangled up with either of these beasts. While traveling ridgelines, give yourself an extra safety margin with what appears to be the edge, as these impressive wind features are often overhanging. Limit your time spent on slopes beneath these, as a cornice fall can trigger a large avalanche on the slope below. Glide cracks can fail catastrophically or melt in place. During periods of extended warming, avoid being on slopes where the seasonal snowpack is gliding downhill.

Have feedback for us? Let us know how we can serve you better. Special thanks to Friends of FAC for creating this survey: link here.

FAC will issue daily snowpack updates Monday, Wednesday, and Friday through April 28. We may update more frequently if we return to a snowier weather pattern. 

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