Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Thu
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

An Avalanche Watch is in effect until 18:00 this evening. Dangerous avalanche conditions will develop as winds and snowfall increase today and tonight. Fresh slabs will build on leeward terrain, and add stress to a weak layer buried 3-4 feet. Any avalanche today could entrain a large volume of snow, making escape difficult. Wind-sheltered, low-angle terrain will still provide enjoyable conditions. 

The danger may not rise to HIGH until sundown or tonight.

Problemi valanghivi

  • Wind Slabs

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

    Strong southwesterly winds will transport recent snow into fresh slabs on the leeward side of ridgelines, saddles, and in cross-loaded gullies. Up to a foot of expected snow and moderate to high winds will result in obvious dunes and drifts. Cracking in the snow underneath you or your machine is providing bulls-eye data that you’re on top of recently drifted snow and should steer you toward more sheltered terrain. 

    Snow will be actively transported today and reactive slabs of recently drifted snow will form quickly.  Expect the surface to change as the day progresses and plan accordingly. Don’t hem yourself in by only having one egress route out of the terrain you are in. 

    Steep, sheltered terrain that receives 8 inches or more of snow today could present a storm slab problem.  Any sluffing indicates a potential loose snow problem. Maintain awareness of what is below you and steer clear of steep convexities above consequential terrain(like cliffs, trees or gullies).

    Cracking in the surface snow, such as this, is a great indicator of recently transported snow that is forming into a slab.  Steer to more sheltered terrain and give areas undereneath ridglines plenty of room.

    Photo: Jeff Metsky

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Don’t lose sight of the weak faceted snow that sits atop (or several inches above) the early February crust. This layer will be buried 3-4 feet below the surface. An inch of water throughout the day combined with active wind-loading may be enough weight to awaken this weak layer. Shaded, northerly aspects above 6,500’ are the most suspect. Yesterday (Tuesday) I found the weak layer in the northern Swan Range. A fatality associated with these facets just north of the border, near Fernie, implies its presence in all three of our forecast zones. 

    Winds will actively load the same slopes today where this facet/crust combo exists. I would give shaded upper elevation slopes lots of room today as any avalanche that breaks on this weak layer will likely be large to very large and entrain a significant amount of snow. Avalanches on this layer may break further than you expect, run long distances, and be difficult to escape.

    PST 68/100 END.  Tests like this still show instability within the buried facet/crust combo.  

    Photo: guy zoellner

Avalanche Discussion

Storm days are the best. The raw power and artistry of Mother Nature doing her thing are always fun to watch. The sculpting of the wind on recent snow will leave us with a new masterpiece in the mountains. Danger will rise throughout the day.  If the forecast verifies, we will reach HIGH sometime this evening.  We've listed upper elevations at HIGH in all zones in case things come in a little earlier or spicier than anticipated. 

There are several things to remember as we take in the fresh slate over the next few days.

1). There is uncertainty about the timing of the storm today and snowfall amounts.  Keep in mind that the hazard will INCREASE throughout the day.  IF storm totals for wind and snowfall deliver as predicted then the danger rating will rise to HIGH.

2). Don’t forget the buried weak layer. We haven’t received any reports lately of the facet/crust being reactive in stability tests. And we haven’t heard of an avalanche in our forecast area associated with this layer for a week. But people keep finding the structure present, and it is going to get a rapid load over the next 24 hours.  

3). There is plenty of snow available for transport and all three ranges are forecasted to see Southwest winds in the 30’s and an additional 10-20 inches of snowfall. Fresh wind-slabs will be easy to find over the next several days. Give these slabs a few days before venturing across them to find better snow in the sheltered terrain.

4). There is a chance of freezing levels reaching 5,000 feet.  If you start to see rollerballs in the lower elevations or snow falling out of the trees then seek out lower angle terrain.  

Storm days such as this are great times to get wheelies on the snowmobile locked in, or explore low angle old growth spruce powder turns. There is plenty of fun terrain to be had without entering up on slopes that are dealing with fresh loading.

Regioni coperte