Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous conditions exist at mid and upper elevations. Saturday, there was a string of close calls and one incident where a rider was caught, carried, and partially buried. Weak layers buried up to four feet deep cannot be trusted. Additionally, winds today will thicken existing slabs, so the danger will rise through the day. Stick to terrain that is sheltered from the wind and keep slope angles less than 30 degrees.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4

    On Saturday, a group of riders in the Flathead Range observed a very large avalanche that broke several hundred feet wide and ran almost 2000 vertical feet. A rider in the Swan Range was caught, carried, and partially buried in a slab that broke several feet deep. Another rider had a close call on a southerly aspect in the Whitefish Range. Apply the lessons from these events to your travels today. Stay off of slopes steeper than 30 degrees above roughly 5500’ where this layer is proving more reactive. Avalanches triggered on layers buried deep within the snowpack will be difficult to survive.

    (2/20/2021) Looking across the bed surface from a corner of a very large avalanche remotely triggered by a party on the Flathead Range. The slide broke below them and took out their track from an earlier run.

  • Wind Slabs

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

    Winds picked up to speeds capable of transporting snow overnight and will continue throughout the day. Saturday, Clancy observed shooting cracks and noted that cornices were easy to trigger. This is only the beginning. Light snow showers will add additional fuel to winds that will gust up to 50 mph. Avoid leeward facing slopes below ridgelines and watch for drifted snow further downslope. Seek out terrain that is sheltered from the wind and give yourself a wide margin for error since a small wind slab is capable of stepping down to a much larger hard slab avalanche.

    (2/14/2021) null

Avalanche Discussion

The weak layer that formed during the late January dry spell is DANGEROUS. Yesterday (Saturday) in the Flathead Range, a group of experienced riders performed a variety of snowpit tests on a slope adjacent slope to one that later avalanched. What is spooky about the avalanche is that the group had no signs of instability on their way up. It also occurred on a west-facing aspect. Although it has been clear that the weak layer exists, this is the first reported avalanche on a west aspect. The hot spots for avalanche activity have been north and east-facing slopes above roughly 5700’.

Another incident occurred in the Swan Range where a group of riders triggered a slab avalanche that deposited debris up to an estimated 20 feet deep. The slope failed under the second rider. Thankfully, this rider ended up on top of the debris and was partially buried with his head and arm out of the snow. The party reported that this avalanche stepped down to weak layers buried near the ground. These weak layers were the ones responsible for widespread avalanche activity earlier in the year. There is a higher degree of uncertainty if this is the beginning of a new trend or an outlier. For now, it is best to view it as a possibility and give yourself a wider margin for error by staying further away from runouts of large north and east-facing avalanche paths.

A driver in today’s forecast is the impressive wind speeds out of the west and southwest. Winds are expected to exceed 50 mph at the highest ridgelines. Expect these winds to transport any loose snow that is available onto easterly and northerly facing slopes. I’d also expect to find slabs in cross-loaded terrain features and in odd places as winds get churned around at middle elevations. This will be an obvious hazard today. Actively drifting snow and pillowy-looking surfaces are your signs to take shelter from the wind. This additional snow is going to get transported onto aspects that face north and east where buried weak layers are proving most reactive. Dial back slope angles like you have hopefully done so already.

Pro tip: How do you measure steepness? An inclinometer is the tool. Personally, my trusted compass with an inclinometer now remains buried in my pack and got replaced last week with the app Theodolite. It took me a while since I have an “old school” mentality, but this app is easy to use. It allows for the quickest and easiest way to field-proof slopes around you to ensure that you aren’t playing the guessing game on slope angles. Now more than ever is a time to double-check yourself.

We thank everyone for submitting observations and reporting their close calls. This information is incredibly valuable to accurate forecasts and to the entire community. We can only publish observations for public viewing if you add contact information. We encourage you to do so and know that your contact info remains anonymous to the public. Thank you. 

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