Posted:
Feb 13, 2016 @ 6:31 am

The current avalanche danger is Moderate in the west central Montana backcountry on steep slopes(>35 Degrees).  Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for February 13, 2016. 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

Temperatures are below freezing in all mountain locations.  Winds are 26 mph with gusts of 40 mph out of the WNW.  The advisory area received 1 to 3 new inches of snow in the last 24 hours.

Steve and I toured in the Rattlesnake yesterday.  Brian was in the Bitterroots for the last 3 days.  We all found similar conditions.  The snow surface was wet and we saw many wet loose avalanches.  With the temperatures dropping this morning the snow surface will refreeze.  The snow line is around 4000 ft.  We are currently receiving snow in the mountains and have high winds.  The question to ask today is, how is the new snow bonding to the old snow surface?

The main problem today will be loose dry avalanches.  These are usually not a problem unless they take you into a terrain trap (cliff, gully, or tree).

The second problem are wind slabs.  As the region accumulates more snow look for active transport by the wind on leeward slopes.

 

Weather and Avalanche Outlook

A cold front entered our area and is dropping the snow level to 4000 ft.  This weather pattern will bring with it moderate snow bursts with high winds.  This system will move out of area tonight and be replaced by a more powerful one.  The new system will bring the possibility of heavy snow and strong winds.  By Monday the snow level is expected to rise to 6000 ft.  With these conditions the avalanche danger will increase.  Conditions can change rapidly while in the backcountry, pay attention to red flags (shooting cracks, recent avalanche activity, and sudden collapses).

Ski and ride safe.  I will issue the next advisory on Tuesday.

READ FULL ADVISORY  

Problem 1 - Loose Dry

  • TYPE

    loose-dry

    Loose Dry

    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

    1-2

    < 1 (Small)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-3

    Possible

    The likelihood of an avalanche resulting from this problem.

New snow instabilities on slopes > 35 degrees.

Problem 2 - Wind Slabs

  • 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

    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.

With new snow available for transport look for wind slabs on leeward slopes.

GALLERY

Pt Six Data Plot 2_12_16
Pt Six Data Plot 2_12_16
rattlesnake roller balls
rattlesnake roller balls
rollerballs rattlesnake 02:12:16
rollerballs rattlesnake 02:12:16
rattlesnake 02:12:16
rattlesnake 02:12:16
rattlesnake2
rattlesnake2

Gallery 02/13/2016

FORECAST & OUTLOOK

New snow and high winds through Monday.

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.