Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Be sure to check the bonding of the recently fallen snow to the underlying crust on Thursday. This will give you information about both the depth and reactivity of any potential avalanche. If you see new avalanches or find a poor bond, default to lower-angled slopes.

Problemi valanghivi

  • Wind Slabs

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

    If you’re going to trigger a slab avalanche on Thursday, it will likely be in wind-loaded terrain at upper elevations. Look for textured surfaces or areas that look “fat” compared to the surrounding landscape to identify wind-loaded features. Using test slopes and hand pits as you travel can give you an indication of the snow’s slab potential and how well it is bonded to the old snow surface. Pay close attention near ridgelines, unsupported slopes, or rocky terrain where you’re more likely to trigger one of these small avalanches.

    (4/11/2023)

    A skier-triggered slab in the new storm snow on 4/11. [N 5000']

    Photo: Public Observation

  • Loose Wet

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

    Periods of sunshine or daytime warming could result in Loose Wet avalanches occurring on steep slopes. If the surface is wet and sticky and you notice snow shedding from trees and rocks or new rollerballs, then wet avalanches may soon follow. Although they may start small, they have the ability to entrain snow and grow large as they descend, sometimes triggering slabs in the process. Your best management tool will be to head for lower-angled slopes keeping aware of overhead hazards.

    (4/12/2023)

    New rollerballs started with just a little sunshine on 4/11. These are often the precursor to Loose Wet avalanches.

    Photo: Dallas Glass

Avalanche Discussion

After several days of rain at Snoqualmie Pass earlier this week, upper elevations picked up roughly 6-9 inches of new snow on Tuesday, with considerably less down low. NWAC forecasters visited the Alpental Valley on Tuesday and Commonwealth Basin on Wednesday. In both locations, they found that the new snow was poorly bonded to the underlying surface. In some cases, the storm snow was easy to trigger with ski cuts on test slopes. They also confirmed a widespread natural cycle due to the aforementioned atmospheric river that dropped over 2 inches of precipitation (SWE) on our cold wintertime snowpack. On Wednesday, multiple new wet avalanches were observed due to daytime warming and direct solar input on the recently fallen snow. The 4/11 crust varied in thickness and stoutness across the landscape.

For several days, we have been talking about large and unpredictable shedding avalanches such as Glides shaping your travel plans. Although we have dropped these difficult-to-forecast events from the official problem list for Thursday, keep them in the back of your mind. Don’t linger on slopes where you see crevasse-like cracks or hanging blocks of snow on rocky ledges. At some point, all of that snow has to come down during the spring, we just don’t anticipate widespread enough activity on Thursday for an official problem.

Barring some unforeseen scenario, this is my last forecast for the season. I wanted to take a minute to thank everyone who submitted observations and helped us out. Have a safe and fun spring touring season. See you in the fall!

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