Avalanche forecast

Presidential Range

Mount Washington Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
Treeline
2 · Moderate
Below
No rating
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Highlights

You could trigger an avalanche in new, wind drifted snow on steep east and south-facing slopes today. Watch out for areas of deeper snow, shooting cracks under your feet, or blowing snow from ridgelines as these are signs of the avalanche problem. Traveling on the icy, old snow surface will help to limit your exposure to this hazard. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Expect to find variable conditions across terrain today. With falling temperatures, the saturated snow is now refreezing which will create a slick and icy surface. Today, new snow and increasing northwest winds could begin to build small wind slabs across south and east-facing terrain features at middle elevations that could be sensitive to the weight of a person. These will be easy to identify as the new snow will appear bright white and in contrast to the textured and icy old snow surface. 

    Lookout for accumulations of deeper drifts today and signs of instabilities like shooting cracks. Look to see if snow is moving and blowing from ridgelines and beginning to build wind slabs as this is a sign that the hazard is increasing. Careful evaluation from visual clues, paying attention to changing snow depths, and using hand shears and column tests to assess sensitivity will be helpful decision makers today. You can also reduce your exposure to the wind slab hazard by traveling on the icy, old snow surface where you are unlikely to trigger an avalanche.

Avalanche Discussion

Subfreezing temperatures for the first time in 4 days will begin to freeze yesterday’s wet and saturated snowpack, which will stop additional melting. The concerning strong-over-weak structure that was observed earlier this week is no longer a concern and this freeze will help to stabilize any remaining instability. Because of this, today’s avalanche concerns are a surface snow issue and nothing deeper in the snowpack. 

Recent models have this storm system tracking further east, which will limit total snow accumulations from this storm. The good news, however, is that temperatures are trending cooler in ravines so most if not all the precipitation will fall as snow.

The composition of today’s wind slabs will be driven by ramping winds, so they will likely have a strong-over-weak structure on a firm and refreezing surface. The icy conditions will require mountaineering tools and the skills to use them. This could also create slick conditions that could result in a slide-for-life fall in steep terrain. This slick and icy surface will also act as an effective bed surface as newly wind drifted snow will struggle to bond to it.

Today we have only listed the avalanche problem at middle elevations and this accounts for significant snowpack loss at upper elevations and high wind speeds. MWOBS reported 16 inches of snow at 7:00 AM on the 27th, and by 7:00 AM on the 28th only listed 2 inches. This was mostly due to fog eating away at the snowpack, and compounded by rain and sustained warm temperatures over the week. Rocks are clearly visible and upper elevations and even start zones of steep skiing in ravines are thinner and rockier. With limited snow to fall on, there is not much of an avalanche problem at upper elevations. 

The other component is the strong to extreme wind speeds accompanying this storm system. Northwest winds are forecast to ramp and rage throughout the day with wind speeds increasing to 85-100 mph and gusts up to 110 mph and this will work to scour upper elevations. Middle elevations could develop smaller and less sensitive wind slabs as well because of the high wind speeds.

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