Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

New snow and strong winds will make both natural and human triggered avalanches likely. Avalanche danger will increase through the day as the storm progresses. Some of these avalanches could fail 3-6 feet deep on buried weak layers and produce large and potentially unsurvivable avalanches. 

If you are involved in an accident today, rescue could be delayed or extremely difficult with the gale force winds. In short, today is not the day to mess with avalanche terrain!

There will be excellent skiing and riding on wind sheltered/low angle slopes. Avoid the avalanche problem today by sticking to slopes under 30 degrees without avalanche terrain above them.

The Considerable danger at low elevation is specific to Lolo Pass. Elsewhere at low elevation where the new snow is falling on dirt, avalanche danger is Moderate with the primary concern being larger avalanches running from above into low elevation terrain. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    With a foot or more of new snow already on the ground and another 2+ feet expected today, there is no shortage of snow available for wind transport. Today, a major wind event is impacting the area with steady ridgetop winds of 50mph and gusts to the 70s. Expect snow to be blowing around today and forming very reactive wind slabs in the new snow. 

    With wind speeds this strong, be alert for unusual wind loading locations. Expect to see wind slab lower on the slope than you normally would, or to see usually sheltered terrain develop wind slab as the strong wind reaches into sheltered terrain. 

    Observations are already showing sensitive wind slabs ahead of the new snow and current storm. On Tuesday, WCMAC staff found reactive windslab in the Brushy Fork of the northern Bitterroot. In the southern Bitterroot, multiple observations showed wind transport and fresh wind slabs earlier in the week.  By the end of the day today, expect wind slabs larger and more dangerous than anything we have seen in observations this week. 

    Slope angle will be the only way to avoid this problem. Avalanches are unlikely on slopes under 30 degrees in slope angle. Avoid low angle terrain with steeper avalanche terrain above as avalanches could be remotely triggered or fail naturally. 

    Lolo Pass falls within the low elevation band. Although this band is not shaded in the location infographic, expect reactive wind slabs above Lolo Pass! 

    Photo: Cam Mackenzie

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    Keep it simple... multiple weak layers of buried surface hoar, buried near surface facets, and crust/facet layers were buried 1-3 feet deep at the start of this storm. By now, these layers are buried 2-4 feet deep with potential to be buried by a 4-6 feet slab of snow by the end of the day today. This is a serious load that will stress buried weak layers and likely fail naturally. 

    Coupled with the wind and connected slab across multiple start zones, we could see some of these persistent slab avalanches reach D3+ in size. 

    Like the wind slab problem, low angle slopes free from overhead hazard are the only way to avoid this problem today. Today is not the day to tempt fate or mess with this avalanche problem. If you are caught in one of these avalanches, it could be unsurvivable. 

    (3/7/2026)

    Tracks and crown of a large skier-triggered avalanche in the backcountry terrain adjacent to Lost Trail that was triggered on March 6th. The avalanche failed around two feet down on a layer of surface hoar that was buried in mid-February.

    Photo: Ben VandenBos

Avalanche Discussion

There is a lot going on with this storm, but in some ways it is very simple. If this storm delivers as promised, avalanches will be likely… stay out of avalanche terrain… end of discussion! 

Overnight snow totals are difficult to tell right now with SNOTEL sites showing a SWE (snow water equivalent) of between .2 to 1.7 inches of water and new snow totals that do not line up with in field observations. Either way, expect to see a foot or more of new snow at upper elevation this morning in all areas except the Rattlesnake which may have less. Today, the main snow event arrives with some  impressive totals. From north to south: 

Rattlesnake: 14-15 inches expected today

Northern Bitterroot: 13-15 inches expected today

Central Bitterroot: 19-23 inches expected today

Southern Bitterroot: 18-24 inches expected today

Where today becomes weird is the wind. Remember, weird weather makes weird avalanches. 2 feet of fresh snow and 70mph wind definitely falls in the weird or unusual category. Expect to see avalanches in unusual areas today. 

As the wind event dies down, we will likely transition to a storm slab problem as well. Another round of heavy snow arrives this evening. If you are out in the mountains later this afternoon into evening and the wind isn’t blowing, don’t let your guard down and be alert for fresh storm slabs. 

What happens if the storm under performs and we don't see over a foot of new snow today? In that case, expect avalanches to still be reactive to the weight of a human. There is enough snow already on the ground to form reactive wind slabs. Avalanche size may decrease, but chances of triggering remains likely. 

Please submit an observation to let us know what you see in the mountains today. It can be as simple as letting us know how much new snow fell in your area. Every bit of information helps, especially during large storm events.

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