Avalanche forecast

Hatcher Pass

Hatcher Pass Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The avalanche danger is MODERATE  for  WIND SLABS at upper elevations. Above 2500', there is still a chance you could trigger a large PERSISTENT SLAB avalanche on old weak snow near the ground. Low elevations have improved coverage and limited hazard.

Today, mostly dry northwest flow will bring increasing winds and falling temperatures. Snowfall is possible, but accumulations look to remain minimal. 

Look for drifting snow, fresh pillows, lenses, and smooth slabs formed by strong winds. Cracking, collapsing, and drifting snow are indications of this problem. When in doubt, choose lower-angle slopes or sheltered terrain. 

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Avalanche problems

  • Wind Slabs

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

    Yesterday's storm arrived with moderate to strong southwest winds. These were enough to easily transport recent light-density snow and create fresh drifts and wind slabs before the freezing drizzle began in earnest. What this means is that between yesterday's southerly winds and today's northerlies, it's possible to encounter fresh drifts and wind slabs up to 2' deep on all aspects in upper elevation terrain. While a cooling trend today will help lock things in place and improve stability, remember that most avalanches happen within 48 hours of a storm. 

    Today, increasing northwesterly winds will work to transport any available snow. Yesterday's freezing drizzle likely formed a thin zipper crust that could help keep this problem at bay by generally limiting snow available for transport. 

    • Expect wind slabs to increase in size, likelihood, density, and distribution as you climb in elevation.
    • The freezing drizzle will have capped most dry-loose potential with a thin crust at mid and lower elevations, but it's possible some upper elevations remain protected and saw only snow throughout the day yesterday. 
    • Look out for cornices, fresh drifts, and round lenses of snow at ridgelines, on cross-loaded gullies, and steep convex rolls.

    Pole probing and hand pits can help identify dense over light snow and help locate this problem. Smooth, hollow-sounding slopes, cracking, and collapsing are all indications that you're on a slope with strong over weak snow. Select lower-angle slopes that are less loaded or more protected. Ski one at a time and choose terrain with open runouts free of rocks and cliffs. 

  • Persistent Slabs

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

    Over the last week, Hatcher Pass has picked up about 16'' of snow and nearly 2'' of snow water equivalent. All this new snow is adding weight and stressing old, buried weak layers near the ground. While we have observed no natural or human-triggered avalanches on these layers in over two weeks, the snowpack structure remains fair at best, and this problem remains possible.

    While trending more unlikely, it remains possible for a skier or rider to still trigger an avalanche over 3' deep on weak snow near the ground.

    • This problem is most pronounced on steep, open, rocky, upper-elevation slopes where the snowpack remains thin and shallow.
    • Mid-elevation terrain harboring old weak snow on the ground could produce the same problem. Steep gullies are where you'd find it. 
    • Small natural or human-triggered avalanches could accumulate weight and step down into these deeper weak layers, increasing the size and consequence of smaller avalanches. 

    The easiest way to manage this problem is to select terrain with a steepness of less than about 30 degrees. If you do choose to get into avalanche terrain (slopes steeper than 30 degrees), select slopes with a uniformly deep snow pack greater than about 3' deep—although be aware that you could trigger a slide from the edges or the middle of a slope where the snowpack is shallow and variable. 

    Photo: Hatcher Pass Avalanche Center

    Snowpack profile from Eldorado earlier this month shows weak snow persisting near the ground. 

Avalanche Discussion

Yesterday, our favored southwest flow brought low clouds and freezing drizzle. 6-8'' of forecasted snow proofed out to about 3'' @ .5'' H20 and a new thin crust on last week's light powder. Settlement generally outpaced accumulation, and any gains were tough to quantify. While this wasn't the Valentine's gift we'd hoped for, a generally active week has left Hatcher Pass with more than a foot of new snow and nearly 2'' of SWE. 

What this means is overall improved coverage and conditions. While yesterday's freezing grizzle will have created a weak zipper crust near the snow surface, and today's wind will work to transport any available snow, expect a clearing and cooling trend to lock things in place and rapidly improve stability. Cold temperatures this week will work to decompose crusts and loosen the snow surface, further improving conditions. As skies clear and you start to venture into more exposed terrain, there are a few things to keep in mind:

  • Within and just under our last week's snow, there are several crusts, old facets, some surface hoar, and density changes that produced mid-storm instabilities. So far, these have not translated into lingering instabilities, but if you're jumping into steep, upper-elevation terrain, be ready for small pieces of snow to start moving. 
  • Weak snow near the ground is still a concern and we just added 2'' of SWE to the scales. Things are trending in the right direction and it's been over two weeks since our last human-triggered persistent slab avalanche, and longer since any natural activity. Skier and riders are only starting to scratch the surface of our plethora of steep, upper elevation terrain. In shallow and rocky areas, it remains a possibility to trigger a large avalanche on weak snow near the ground. Kicking off a small piece of snow could lead to accumulating weight on the slope, and even a small avalanche could step down into these buried weak layers. 
  • While depth and structure are improving, the snowpack remains generally thin. As you move into steep terrain, watch your speed and look out for rocks and other hazards. 

RECENT AVALANCHES: 

Yesterday, visibility was obscured, and no new activity was observed or reported. Thursday, a party triggered a D1.5 soft slab on the southwest aspect of Marmot at about 4,300'. On Friday, a skier triggered a similar slide on a similar aspect on Marmot. Between Wednesday and Friday, forecasters observed several dry, loose avalanches in steep, craggy terrain and small wind slabs on steep, wind-loaded slopes. These were all small D1s that likely ran naturally during a bump in winds on 2/10-11. See all recent observations here.

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