Posted:
Mar 21, 2017 @ 6:21 am

The current avalanche danger is LOW for the west central Montana backcountry.  Human triggered avalanches are still possible in isolated terrain.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 21, 2017.  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 29 F to 34 F in the region. Winds are 16 mph with gusts of 23 mph out of the SE in the Bitterroot. Point Six, in the northern part of the advisory area, winds are 12 mph with gusts of 16 mph out of the ESE.  The area received 0 to 1 new inches of snow. The new snow had SWE’s ranging from .1 to .2 inches of water.

Logan and I took the sleds to Granite Pass in the northern Bitterroot yesterday.  Josh is at Yurtski in the southern Swan.  We all found a snowpack that was locked up due to the freezing temperatures in the mountains.  With very little sun and high winds, the snowpack did not warm above freezing yesterday. Temperatures are rising this morning and most snotel sites got below freezing last night again locking up the snowpack.

The primary avalanche problem is loose wet releases in the afternoon.  With warming temperatures and intermittent showers, today look for roller balls and pinwheels.  These are clues to surface instability, and it is time to change aspects.

The secondary avalanche concern is cornices.  Warming temperatures are weakening cornices. Give them a wide berth.

Avalanche and Weather Outlook

Warming temperatures today and possible showers with light accumulations.  Temperatures should drop below freezing tonight above 6000 feet.  With wind and cloud cover the avalanche danger should stay the same.  If the sun does come out, look for the avalanche danger to rise on sun-exposed slopes in the afternoon.

If you are out in the backcountry, please send us your observations, these are very helpful in producing the advisory.  I will issue the next advisory on March 23, 2017.

Ski and ride safe.

 

READ FULL ADVISORY  

Problem 1 - Loose Wet

  • 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

    2-3

    1 (Small)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-2

    Unlikely/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
    W - West

When you start to see roller balls or pinwheels it is time to change aspects.

Problem 2 - Cornices

  • TYPE

    cornices

    Cornices / Cornice Fall

    Release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the down-wind side. They range from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (~10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice fall can entrain loose surface snow or trigger slab avalanches.

  • SIZE

    4-5

    2 (Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-1

    Unlikely

    The likelihood of an avalanche resulting from this problem.

With warming temperatures cornices will weaken.  Give them a wide berth and cornices have a tendency to break farther back than anticipated.

VIDEO

Northern Bitterroot 03/20/2017

GALLERY

Northern Bitterroot
Northern Bitterroot
Cloud Cover
Cloud Cover
N Bitterroot
N Bitterroot
Wind and Cloudcover
Wind and Cloudcover
Clouds
Clouds

Observations 03/20/2017

FORECAST & OUTLOOK

Warming temperatures today and possible showers with light accumulations. Temperatures should drop below freezing tonight above 6000 feet. With wind and cloud cover the avalanche danger should stay the same. If the sun does come out look for the avalanche danger to rise on sun exposed slopes in the afternoon.

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.