Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Increasing winds will build varying layers of dense snow over stubborn drifts. Monitor density changes within the surface snow, especially as you climb in elevation.  Keep in mind that even brief periods of sunshine will increase avalanche hazards.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Recent light snowfall and southwest winds formed thin slabs which may be reactive to the weight of a rider. Rob and Cam were outside Swan Lake and found touchy pockets of wind-drifted snow and blowing snow yesterday at upper elevations. Wind speeds at the Aeneas Ridge weather station included 15 hours of winds strong enough to drift snow throughout the day yesterday. 

    Expect wind slabs to be thickest, widest, and most common at upper elevations. To identify places within the terrain that may hold wind-loaded drifts, look for pillows or dune-shaped features near ridgelines, cross-loaded gullies, or around the sides of chutes. While choosing terrain, think of the consequences of being knocked off your feet, dragged into a tree, or pushed over rocks. You can avoid the problem by choosing terrain where the snow is sheltered or being scoured by the wind.

    (1/1/2023)

    A well-developed cornice line from southwest winds cross-loading mid-elevations.

    Photo: Mark Dundas

Avalanche Discussion

The wind is the primary driver of our avalanche problems today. The extreme southwest winds recorded on Tuesday morning, followed by increasing northwesterly winds today will warrant your attention. Anticipating conditions to change as you climb in elevation is a good start. Yesterday, observers reported stubborn drifts on typical leeward aspects. Today these drifts will be covered with building wind slabs from shifting west and north winds. Expect freshly formed wind slabs to be more sensitive to human triggering.

In addition to the listed avalanche problems, the potential for the sun to make an appearance is uncertain. Behind the scenes of writing this forecast, Cam and I have been pouring over weather models in the early morning hours, in the hopes of predicting this afternoon's mix of clouds and sun. It can be a challenge to accurately predict the timing and amount of cloud cover. More specifically, the angle of the sun in March has increased and solar radiation is far more intense today, as compared to mid-winter. Even short periods of sunshine pack a punch on warming the surface of recent snow. If we do see brief periods of strong solar input, be aware that avalanche activity may include loose wet slides and cornice falls. If you start to see roller balls on the slopes you are riding, get ahead of this instability and move to shady aspects.

Fireside/Snowpack Wednesday, March 15. Join us for a virtual evening combining two favorite community ed workshops. FAC Forecaster Cam Johnson will kick things off with a State of the Snowpack presentation to help you digest the current conditions and plan your next trip. Then we'll shift to Fireside Chats for open dialogue about human and avalanche factors. A recreationist, forecaster, and avalanche educator all experienced a near miss in the first three weeks of February. Together, Kat, Cam, and Meg will explore the tough decisions, tricky snow, and lessons learned from their experiences. No registration is needed; click here for Zoom. The event will begin at 6 p.m. 

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