Posted:
Dec 24, 2018 @ 5:28 am

The current avalanche danger is HIGH in the west central Montana backcountry on wind loaded slopes. Travel on wind loaded slopes or in runout zones is not recommended today. All other slopes are CONSIDERABLE.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for December 24, 2018.  This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 20 F to 28 F in the region.  In the Bitterroot winds are 3 mph with gusts of 4 out of the SE.  In the northern part of the advisory area, winds are reading 2 mph with gusts of 6 mph out of the East.  The forecast area received 6 to 14  inches of new snow in the last 24 hours.  The SWE totals range from .4 to .9 inches.

The primary concern today is wind slabs. Look for snowdrifts and smooth, rounded deposits of snow on ridgelines. Avoid traveling on wind drifted terrain. Do not travel in runout zones below wind loaded terrain.

The second avalanche problem is persistent slabs. Look for red flags such as whumpfing, collapsing and shooting cracks. Dig a pit to the ground and look for our buried layers and see how reactive they are in stability tests. Avoid traveling under runout zones and think of what terrain is above and below you. The layers in the snowpack are reactive to human triggers and are widespread throughout our forecast area. Travel and recreate on slopes less than 25 degrees.

Bottom line: The snowpack needs time to adjust to the new snow. Travel and recreate on slopes less than 25 degrees. Do not travel in runout zones.

 

Avalanche and Weather Outlook

More snow throughout the day. See the forecast here.

If you do make it out into the hills feel free to share what you see on our public observations page. They are not only helpful to your community but extremely helpful to us.

Ski and ride safe.

READ FULL ADVISORY  

Problem 1 - Wind Drifted Snow

  • TYPE

    wind-slabs

    Wind Slabs

    Release of a cohesive layer of snow (a slab) formed by the wind.  Wind typically erodes snow from the upwind sides of terrain features and deposits snow on the downwind side.  Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

  • SIZE

    5-6

    2-3 (Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-7

    Very Likely

    The likelihood of an avalanche resulting from this problem.

  • IMAGE

Look for snowdrifts and smooth, rounded deposits of snow on ridgelines. Avoid traveling on wind drifted terrain. Do not travel in runout zones below wind loaded terrain.

 

Problem 2 - Persistent Slabs

  • 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

    4-5

    2 (Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-5

    Likely

    The likelihood of an avalanche resulting from this problem.

  • IMAGE

Look for red flags such as whumpfing, collapsing and shooting cracks. Dig a pit to the ground and look for our buried layers and see how reactive they are in stability tests. Avoid traveling under runout zones and think of what terrain is above and below you. The layers in the snowpack are reactive to human triggers and are widespread throughout our forecast area. Travel and recreate on slopes less than 25 degrees.

 

FORECAST & OUTLOOK

  • Danger Trend

    increasing

    Increasing Danger

  • Area Forecast

    New Snow

See the forecast here. Look for the avalanche danger to increase with additional loading from new snow.

If you do make it out into the hills feel free to share what you see on our public observations page. They are not only helpful to your community but extremely helpful to us.

Ski and ride safe.

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.