Avalanche forecast

Avalanche forecast

Payette Avalanche Center
View on map

Avalanche danger

Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

10-20" of snowfall along with strong SW winds will create dangerous avalanche conditions today. Wind slab avalanches will become very likely above 7000'. Persistent weak layers buried deeper near the ground may become overloaded and fail.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Triggering a persistent slab on weak facets from November has been unlikely. As new snow adds weight and stress to the existing snowpack, we can expect the likelihood to increase from unlikely to possible later today into tomorrow. The old November facets have continued to show signs of strengthening. When will this weak snow near the ground beome overloaded and fail? This is the question to ask yourself if you're out in the mountains this week. As more weight is added, the likelihood of triggering a deeper avalanche on weak snow near the ground increases. In areas where the snowpack is shallow, wind slab avalanches could step down to the November facets. Avalanches this size would be large and destructive. Where are you most likely to trigger a persistent slab avalanche?  Steep, north-facing terrain above 7000', especially where wind is actively loading slopes.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2

    10-20" of snowfall is forecasted during the day today, with more tonight. Strong southwest winds will easily be gusting over 50 MPH at upper elevations. Lower elevations are expected to see gusts 30-40MPH. Dense wind slabs will form quickly today since there was already moderate amounts of snow available for transport before this storm arrived. Wind slabs will become widespread across all aspects and elevations throughout the day. Slabs will be deepest and most reactive above 7000' on north and east-facing slopes. Instabilities within the new storm snow will become increasingly reactive as more snow stacks up. Signs of instability will not be hard to come by today. Days like today, the best advice is to avoid slopes steeper than 30 degrees. Pay attention to the slopes you are adjacent to and underneath. Avalanches will be increasing in size and sensitivity as the day progresses.

    ADDITIONAL DISCUSSION

    New snow is falling on a variety of weak snow. There is 4-6" of very light snow that was on the surface yesterday. On solar aspects, there are crust/facet combinations buried 4-8" down. On shaded aspects, there could be a layer of surface hoar buried 4-8". The new storm snow today will likely not bond well to these existing surfaces and instabilities. In wind-protected areas (if that does exist today), you can expect dry loose snow to be unstable. This dry loose snow (or sluff) will create small avalanches that will be growing in size throughout the day.

Avalanche Discussion

A series of significant winter storms will be impacting our region all week. Today through tomorrow is round 1 of 3 storms that will be bringing large snow totals and strong winds. If you've been reading the forecast or watching our videos (fingers crossed!), then you should be well aware of the poor snowpack structure we've been talking about for weeks now. For the most part, this weak snowpack was lacking a significant slab on top to become a real problem. Well, today that slab is building and it will be continuing to build all week. Snow totals in the mountains could be 2-3 feet by the weekend. Temperatures are forecasted to remain slightly below average for the week. Southwest winds will be moving that light snow around and depositing it into dense slabs at all aspects and elevations.

Avalanche danger will be rising rapidly today. The weather will make mountain travel extremely difficult today. Avalanche conditions will make that travel dangerous. Be alert to changing conditions and remain aware of terrain above you and adjacent to you.

The best way for us to know what's happening as more people are out in the mountains is to submit an observation. Submitting an observation improves your skills, informs other users, and benefits avalanche forecasts. Simple photos highlighting conditions are very helpful.

Did you know there several avalanche classes this month specifically for motorized users? Check out our classes and events page to learn more.