Posted:
Mar 19, 2016 @ 6:29 am

The current avalanche danger is MODERATE in the west central Montana backcountry. Human triggered avalanches are possible. Heightened avalanche conditions exist in isolated terrain. Evaluate snow and terrain carefully and identify features of concern.

Good morning,  this is Travis Craft with the West Central Montana Avalanche Center’s avalanche advisory for March 19, 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

Mountain temperatures range from 11 F to 21 F in the region. Winds are 13 mph with gusts of 16 mph out of the SE in the Bitterroot and Point Six in the northern part of the advisory area is 06 mph with gusts of 11 mph out of the S.  The forecast area received no new snow overnight.

Steve and I toured in the Rattlesnake yesterday.  Ed was in the southern Bitterroot.  We observed small natural loose dry avalanches on steep terrain(>40 degrees).  The main avalanche problem today is loose dry avalanches turing to loose wet avalanches on sun exposed slopes in the afternoon.  These loose avalanches can entrain a lot of snow and could knock you off your feet so, be aware of terrain traps on the slopes you are recreating on.

The second avalanche problem are wind slabs.  These are located on leeward terrain.  Look for scoured snow and hollow sounding snow to identify these slabs.

There are persistent weak layers in the top meter of snow (crusts with facets above and below).  Dig a pit before committing to any steep slope to see if any of these layers are reactive.

Weather and Avalanche Outlook

For the weekend we will be under a ridge of high pressure.  This will cause temperatures to above normal.  With temperatures rising in the day and throughout the weekend, we make the shift back to spring conditions.  If the slope you are recreating on starts to feel saturated or wet it is time to move to a different slope.  The avalanche danger will remain the same with these conditions.

Ski and ride safe.  Logan 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

    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.

Loose Dry avalanches can be triggered on steep slopes.  As the day warms these will turn to loose wet on sun exposed slopes.  There is lot of new snow and these loose wet avalanches could entrain a lot of snow.  These could be a problem if they take you into a terrain trap(cliff, gully, or tree).

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

    3-4

    1-2 (Small-Large)

    The potential size of avalanche resulting from this problem.

  • LIKELIHOOD

    Likelihood-2

    Unlikely/Possible

    The likelihood of an avalanche resulting from this problem.

There are wind slabs on leeward terrain.  We have had winds that were able to transport snow.  Look for scoured slopes and hollow sounding snow.

GALLERY

Steve skinning with surface hoar
Steve skinning with surface hoar
loose snow
loose snow
Steve in the pit
Steve in the pit
03182016LostTrailPass 2
03182016LostTrailPass 2
03_18_16Rattelsnake
03_18_16Rattelsnake

03/19/2016 gallery

FORECAST & OUTLOOK

  • Danger Trend

    same

    Same Danger

  • Area Forecast

    Sunny

High pressure dominates the weekend.  This will bring spring conditions back to the mountains.

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.