Boletín de aludes

Boletín de aludes

Payette Avalanche Center
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Peligro de aludes

Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger will rise to CONSIDERABLE by this afternoon. 5-10" of snowfall, along with SW winds will create soft, sensitive wind slabs 1-2 feet thick, above 7000', especially on N and E-facing terrain. Dry loose avalanches (sluff) will increase in size today in terrain steeper than 35 degrees. Pay attention to how the new snow is bonding, especially on solar aspects that may have a thin crust.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    5-10" of new snowfall (Thursday AM-Thursday PM), coupled with SW winds gusting 20+ MPH will create sensitive wind slabs this afternoon. Before the storm, there was 4-8" of soft, light snow at the surface available for transport. Wind slabs could become 1-2 feet thick later today. You're most likely to find sensitive wind slabs on N, NE, and E-facing terrain above 7000'. Stay attentive to crossloading and changing wind direction loading slopes across the compass. Watch for visual clues like shooting cracks from your skis, board, or sled. If you notice a change from soft and powdery to stiff and "slabby", be heads up for wind slabs. Look for drifts, dunes, or pillows to indicate the presence of a wind slab.

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    In areas of terrain that have not been impacted by the wind, pay attention to dry loose avalanches (sluff). New snowfall is coming in on the lighter side (for West Central Idaho). 5-10" of soft, light snow combined with 4-8" of soft snow near the surface yesterday, means dry loose avalanches could be 12" deep. Be especially heads up for dry loose on wind-sheltered aspects that saw strong solar input yesterday (E, SE, S, SW, W). Some of these aspects could have a thin, melt-freeze crust from yesterday afternoon. Dry loose avalanches may seem benign and manageable, but they can often catch experienced professionals off guard. Be prepared to manage sluff in sustained terrain over 35 degrees, especially near terrain traps like gullies and above big rocks/cliffs. 

Avalanche Discussion

What a week it's been! After nearly two weeks of high and dry to start the month of March, storms began rolling in last Wednesday. Small storms brought 12-18" (1.5-2"SWE) Wednesday through Friday. An atmospheric river opened up the floodgates Saturday through Monday dumping over 3 feet of snow (3.5-4"SWE). Sunday was especially impressive, with over 2 feet of snow and 2-3"SWE over a 24-hour period. Evidence of a widespread, large natural avalanche cycle has been observed since Monday. Crowns spanning hundreds of feet of terrain were observed yesterday. These likely occurred sometime Sunday afternoon/evening. Most of these avalanches occurred on steep, upper elevation slopes, facing N, NE, and E, especially under big cliff bands. Warming temperatures toward the tail end of the storm helped to settle and strengthen the storm snow rather quickly. 

Moving into the end of this week, we are looking at another stormy period of weather. The mountains could pick up another 1-2 feet (1-2"SWE) by Sunday. This will create another round of new snow problems (i.e. wind slab, loose snow, and maybe storm slab). Yesterday, up Lick Creek, I observed a stable, right-side up snowpack of 3-4 feet in depth, overlying the melt-freeze crust buried last week. I did not observe any signs of instability in my tests nor were there any PWLs or notable layers of concern. You can read this observation here. Recent observations have noted some instabilities in the upper snowpack. Some were on density changes from last weekend's storm, another was adjacent to the melt-freeze crust buried last week (this was outside of our forecast zone). You can view these observations here and here. Both observations noted propagation within extended column tests (ECT) between 20-30 hits. These results of instability are varied and have not been consistently observed across our forecast zone. Varied results of instability warrant further investigation. If you're out in the mountains, spend a few minutes to dig down and look at how the recent storm snow has set up. Questions to ask are: how is the new snow bonding to the recent interface; and are you finding obvious facets (weak snow) near a crust?

Want to support your local avalanche forecast? Submit an observation. Submitting an observation on our website is a great way to help forecasters gather more information and improve avalanche forecasts.

Come out and celebrate the beginning of Spring (yes, that's what the calendar says) with the Friends of the Payette Avalanche Center (FPAC) Friday, March 21st at Salmon River Brewery. They'll be at the taphouse starting at 530 PM.