Posted:
Mar 2, 2021 @ 6:06 am

The avalanche danger in the west central Montana backcountry is MODERATE. Evaluate snow and terrain carefully.

Good Morning. This is Travis Craft with the West Central Montana Avalanche Center advisory on Tuesday, March 2, 2021. This advisory is sponsored by the Trail Head. This advisory does not apply to operating ski areas and expires at midnight tonight. The USDA Forest Service is solely responsible for its content.

Snowpack and Weather

Temperatures range from 20 to 28 degrees this morning. Today expect gusty winds in the 40’s and potential for light snow accumulations.

On Friday, there was a natural avalanche in Lost Horse 8.5 miles up the drainage on a South facing aspect that slid, depositing mature timber on the road. There were reports of natural wind slab avalanches in the Rattlesnake. Yesterday, we found reactive facets on the Jan 13 crust in shallow snowpacks in the Brushy Fork. The facets were not reactive in the Rattlesnake in pit tests. This shows us that the likelihood of triggering these avalanches is decreasing, but the consequences are high. The type of avalanche you can trigger will likely be unsurvivable. We observed cornice failure with warming temperatures near Lost Trail Pass. Throughout the advisory area, we saw loose wet releases on steep solar exposed slopes. When roller balls start coming out, it is time to head to shady aspects.

Terrain is the way to combat avalanche problems. Choose slopes less than 30 degrees that are simple and not connected to larger terrain. If you choose slopes above 35 degrees, you increase the likelihood of triggering one of the weak layers deeper in our snowpack, and the consequences will be almost unsurvivable.

Bottom Line

Avoid slopes over 30 degrees. Avoid traveling under large cornices and give them a wide berth on ridges. If roller balls show up move to shadier aspects or head home.

Carry a beacon, shovel, and probe. Reassess conditions throughout the day and stay alert for signs of instability. Dig pits. Look for red flags.

Upcoming Education Events

Please visit our education page for an up-to-date list of regional educational events and course offerings. Below are a few select events and opportunities to check out.

Special Announcements

You’ve prayed, hoped, and danced for snow all winter, and it’s finally here! Western Montana’s mountains are busier than ever before, with new and veteran backcountry users enjoying the fresh snow. To celebrate the snowfall and help ensure everyone has the information needed to enjoy the mountains and return home safely, we bring you Loving La Niña! This virtual fundraising event includes two outstanding gear packages and two ways to enter to win. Please click HERE for more information about this exciting event. All proceeds benefit west-central Montana’s avalanche forecasting and education programs. Together, we can save lives and continue creating the most fun, safe, and responsible backcountry community possible. Spread the word, and spread the love for La Niña!

Public Observations

Thank you to everyone who has taken the time to send in a public observation. Please keep sharing what you find and see while out in the backcountry. This online forum is a great resource to glean information about current conditions.

You can now text us your observations to (406) 219-5566 when you don’t have time to fill out the observations page. Texted observations won’t get posted on the website, but will be used in the development of the forecast.

Ski and ride safe.

READ FULL ADVISORY  

Problem 1 - Persistent Weak Layers

  • TYPE

    persistent-slabs

    Persistent Slabs

    Release of a cohesive layer of soft to hard snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks.  Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Persistent, Deep-Slab.

  • SIZE

    5-6

    2-3 (Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-3

    Possible

    The likelihood of an avalanche resulting from this problem.

  • ADDED DANGER

    Increased Slope Danger

    Increased/Added Danger

    There is an increased risk of avalanches on these slopes:

    N - North
    NE - Northeast
    E - East
    SE - Southeast
    S - South
    SW - Southwest
    W - West
    NW - Northwest

While stability has improved in many areas we still are seeing propagation on near surface facets, buried surface hoar, and the January 13 crust/facets combo. It is possible to trigger an avalanche on these surfaces.

Mid elevations and areas that are shallow have weak faceted snow as the base. These have been collapsing under the weight of skiers and we are seeing propagation in tests. It is possible to trigger these deeper layers. Shallower avalanches or cornice fall may step down to these deep persistent layers causing large destructive slides.

Where depth hoar, basal, or near surface facets exist, avoid slopes over 30º and provide wide margins below and adjacent to avalanche slopes.

Problem 2 - Wet Snow

  • TYPE

    loose-wet

    Loose Wet

    Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose-Dry Avalanches,they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose-wet avalanches can trigger slab avalanches that break into deeper snow layers.

  • SIZE

    3-4

    1-2 (Small-Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-3

    Possible

    The likelihood of an avalanche resulting from this problem.

  • ADDED DANGER

    Increased Slope Danger

    Increased/Added Danger

    There is an increased risk of avalanches on these slopes:

    E - East
    SE - Southeast
    S - South
    SW - Southwest

With warming temperatures and if the sun comes out look for loose wet activity on low and mid elevations today.

Cornices are wearing with the warming temperatures and should be given a wide berth.

GALLERY

Lolopass-pit-2021-01-01
Lolopass-pit-2021-01-01
Jenny bowl, 03:01:2021
Jenny bowl, 03:01:2021
Point 6 windslab, 02:26:2021
Point 6 windslab, 02:26:2021
2_24_21_Central_Bitterroot-StJo
2_24_21_Central_Bitterroot-StJo
ECT P S Missions 02/26/021
ECT P S Missions 02/26/021
Shoot-Creek-01-Mar
Shoot-Creek-01-Mar
20210301LostTrailBackcountry
20210301LostTrailBackcountry
Tree Cones
Tree Cones
Brushy Fork
Brushy Fork

Observations March 01 2021

FORECAST & OUTLOOK

Today light snow accumulations above 4000 feet and gusty winds. High pressure enters the area on Wednesday. See the forecast.

This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.