Lawinenlagebericht

Bitterroot

West Central Montana Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Rising temperatures, clearing skies, and sun will rapidly warm snow surfaces today at all elevations. South and west aspects will be most affected. Wet loose avalanches are likely and could grow large on last week's rain crust. Slab avalanches are possible. Stick to shaded aspects and avoid being on or under slopes with rollerballs and wet snow. Windslab is growing in size today. Avoid easterly upper elevation slopes over 35º.

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    The risk of wet loose avalanches will increase with rising temperatures and sunny skies today. South and west aspects will be the most likely place for wet loose avalanches; however, elevated temperatures could cause the warming of snow surfaces and instability on other aspects. The surface snow sits on a widespread crust that will provide a slick bed surface. Wet loose avalanches could run long distances quickly, entrain considerable snow, and be large enough to bury, injure or kill a person. There is a chance that as the surface snow warms and consolidates, it will release as a slab avalanche on the crust, increasing the size and consequences. Take extra care on sun-warmed aspects today. As the temperature rises and the sun makes an appearance, head to shadier aspects.Rollerballs and trees dropping wet snow signify that things are heating up and the hazard is increasing. Stick to slopes under 35º and avoid being under overhead hazard.Plan your exit from the mountains so that you are not passing under or across south and west facing avalanche terrain late in the day. 

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Wind slab will grow with moderate west winds and strong gusts throughout the day. 

    Rising temperatures will aid the adhesion of wind drifted snow and the growth of wind slab.

    Easterly aspects at upper elevations are where you’ll find wind slab today.

    Watch for wind lips and drifts to indicate wind direction. Hollow sounding snow and shooting cracks are indications of windslab presence and reactivity.

    Avoid wind-loaded start zones over 35º.

    Cornices have grown huge in many areas, today's warming will increase the likelihood of spontaneous cornice fall. Stay well back from the tops of cornices and avoid being below.

     

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    On north slopes above 8000’ in the southern Bitterroot, reactive buried facets could fail with the weight of a skier or rider. These are buried up to 3 feet deep. Southwest winds are adding to the loading. The potential exists for wind slab or cornice fall to step down to this layer. Exercise extra caution in this zone. Avoid slopes over 35º in this zone.

Avalanche Discussion

Since the last forecast, we've had cold temperatures with limited sun. The new snow that arrived on Tuesday has remained light and unconsolidated. Near surface facets grew within the new snow and above the crust that developed during last week's rain, now between five and ten inches deep. Lack of cohesion in the new snow prevented slab avalanches on this slick bed surface and limited windslab formation.

Today the arrival of warmer temperatures and sunny skies will hasten a quick change in the snow. Rising temperatures will consolidate the snow. The sun will rapidly warm surfaces. 

Facets above the crust will provide a weak layer. Wet loose avalanches are likely and could run wider and faster than normally encountered. 

Slab avalanches are possible on the crust and could be triggered by warming, loose wet avalanche, or the weight of a person. 

In the Bitterroot up to ten inches of new snow sits on the crust, which extends up to 8000'. Temperatures will climb higher in this zone today, and it will receive sun earlier. The southern Bitterroot will be warmer than the north. 

As avalanche conditions deteriorate today, so do riding conditions. The areas with the best snow will also be the safest, upper elevation slopes on shaded aspects. 

Sunday brings another change of weather with cooler temperatures, cloudy skies, and the next round of snow. By Monday up to six inches of new snow could fall. Expect deteriorating avalanche conditions with continued snowfall through the week.

Please let us know what you are finding out there. You can submit observations here.

Ski and ride safe.

 

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