Avalanche forecast

Hatcher Pass

Hatcher Pass Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 7 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

The National Weather Service has issued a Winter Weather Advisory for our region through Friday.  

The avalanche danger is CONSIDERABLE above 3500' and MODERATE above 2,500', where intense winds have built Wind Slabs of new snow in specific terrain features. It remains possible to trigger a deeper Persistent Slab avalanche at mid and upper elevations. The danger is LOW at low elevations. 

Today, accumulating snow and strong gusting extreme winds could produce shallow instabilities, but the warm system could more dramatically test buried weak layers and create larger avalanches. 

Look for signs of cracking and collapsing, as well as recent avalanches, as these indicate increased avalanche activity. Travel one at a time and choose slopes with open runouts. Before committing to steep slopes, assess the snowpack for buried weak layers. You can simplify your decision-making by seeking lower-angle slopes or slopes free of terrain traps and exposed rocks. 

SPECIAL ANNOUNCEMENTS:

Thanks for joining us at Blue & Gold Boardshop last night for the State of the Snowpack! 

Winter is here! Come and celebrate with us at the 8th Annual HPAC Cabin Fever Reliever on Saturday, February 7th! More info and tickets here. 

Avalanche problems

  • Wind Slabs

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

    Yesterday, intense winds transported snow at mid and upper elevations, building new drifts. Today, winds have already been gusting strong to extreme out of the Southeast. As you climb in elevation or into wind-drifted terrain, these slides could become larger and easier to trigger.

    • At low elevations and in sheltered terrain, there will be less snow, and it will be less reactive, but in steep terrain such as gully sidewalls, you could still trigger small loose snow avalanches or sloughs.
    • As you climb in elevation into more wind-exposed terrain, stiffer, more sensitive slabs will be likely. These areas are where you might trigger an avalanche that could injure or bury a skier or rider—especially on slopes with gullies, concavities, or cliffs. Cracking and collapsing within the new snow is a red flag and means instabilities exist and avalanches are more likely.

    Look for signs of wind transport such as blowing snow, freshly formed cornices or smooth pillows, lenses or drifts of snow. Pole tests and hand pits are good indicators of slabs. Collapsing ("whumphing") or shooting cracks are indicators of unstable snowpack structure. 

    Shooting cracks were easy to make in areas where intense winds on Wednesday 14 blew snow from S/SW. 

    Photo: Hatcher Pass Avalanche Center

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    We remain in a holding pattern with our persistent slab avalanche problem--we know it exists but it has been stubborn to trigger the last week. Incremental trickles of snowfall following the 1/5-1/6 storm has given our weak snowpack structure time to adjust to new loads. There is some uncertainty about how much new snow water weight our snowpack can handle and how this will translate into sensitivity to trigger. 

    Triggering a deeper avalanche up to 3' feet deep remains possible. 

    • Avalanches will be more likely on slopes steeper than about 30 degrees. 
    • New snow avalanches could step down into old buried weak layers, increasing avalanche size and consequence. 
    • Whumphing and collapsing of the snowpack are indications that there is weak snow failing near the ground. 
    • You may be able to trigger slides in gullies, alpine bowls, or on convex rolls where December's wind formed smooth, firm slabs over weak snow below.

    Before committing to steep slopes, take the time to dig down and assess for these weak layers. You can decrease your risk by riding slopes one at a time and choosing slopes free of exposed rocks, cliffs, or gullies. 

    Large facets at the bottom of our snowpack. With incremental loading, it is not certain that avalanches will be easy to trigger today, but we continue to have an "upside down" structure over loose, angular snow. 

    Photo: Hatcher Pass Avalanche Center

Avalanche Discussion

An extreme weather event is headed into our region today. Warmer temps with rising snow levels and potentially 2"+ of SWE in the next 24-hour period will test our snowpack structure. See the attached weather product for more information. 

Recent Avalanches:

Forecasters in the field yesterday observed several small, natural soft slab avalanches (D1) from the last storm cycle. It has been a week since the last human-triggered persistent slab avalanche. See Thursday 1/8 Microdot avalanche and Pro Observer observation here. 

Regions covered