Karen Rentz snowshoeing through a forest of trees coated with rime ice
Avalanche danger was in the orange to red zone–a high probability of snowy terror and a warning to watch for unattended snowpacks and to be prepared to take action if there were suddenly loud sounds. Terror indeed!
Still, it had been a long winter, with a lot of dangerous weekends in the mountains. We had the special kind of cabin fever that comes only from months of rainy winter Puget Sound weather, when we either turn into lethargic slugs or go screaming madly into the rain.
Weather forecasters back in early autumn predicted a La Niña winter, which would bring colder and wetter conditions to the Pacific Northwest. Nature obliged. Our rain gauge for 2011, so far, was over 20 inches and the snowpack in the mountains was getting thicker by the day. The problem was that there had been alternate patterns of sun, rain, and extreme cold in the mountains, which caused the layers of the snowpack to be unstable (think of a layer cake with the top layer, lubricated by a thin layer of Cool Whip and Jello, avalanching onto the floor in a ’60s sitcom). The avalanche danger everywhere in the mountains was extremely high, weekend after weekend.
We finally decided to head for Hurricane Ridge in Olympic National Park, avalanche danger be damned! Hurricane Ridge is known for treacherous weather and deep snow, so we checked out the forecast, the webcam, and the avalanche danger web sites, and decided that we would be OK if we were careful. The drive to the ridge is about 140 miles from our home, so we left early in the morning, carrying tire chains and extra food and warm clothing.
There was no snow in Port Angeles, gateway to the Olympics, but as we headed up the road, we encountered the first snowbanks and it gradually got thicker as we rose in elevation. Finally, we turned the corner onto Hurricane
Rime ice on the subalpine trees, viewed through icicles on the Hurricane Ridge Visitor Center
Ridge, and saw what we had specifically hoped to see: rime ice coating all the conifer trees, making each tree look like it had been created in a fantasy workshop.
Our northwestern conifers are adapted to winters where the accumulated snow seemingly gets as hard and heavy as concrete. The shape of our subalpine firs and spruces, for example, is tall and slender. Longer branches would break off in the heavy snow, so these species have short branches.
Rime ice is a special kind of ice that forms at windy, high elevations. Water droplets in the atmosphere, at temperatures between -4 and +14°F, become supercooled, staying in liquid form until hurtled against an object. Upon striking that object, the supercooled water suddenly freezes solid. The result? Danger, in the case of an airplane. Beauty, in the case of a subalpine forest.
Rime ice on a weather and radio station; note how the ice crystals grow in straight lines out from the metal of the structure and into the prevailing winds
We had never examined rime ice close up before, and we found that it has a distinct pattern. It grows outward from say, a branch, in a long structure that resembles an opaque crystal (I’m not sure if it technically would be considered a crystal). These linear structures can be over a foot long, and face into the wind. As long as the wind carries supercooled water and as long as the wind comes from the same direction, the formations grow outward in a straight line.
Yet rime ice is not soft like snow, despite its fantasyland appearance. It is hard to the touch; when we tapped it with ski poles, it made a rapping sound rather than collapsing like snow would do. And rime ice only occurred at the places along the ridge where wind would funnel. In the forest just below the open ridge, there was no rime ice (and little snow) on the trees. Interesting stuff indeed!
Looking downslope from Hurricane Ridge: the higher trees are entirely coated with rime ice, while the slightly lower trees have much less ice
Karen and I snowshoed through the rime ice forest along the ridge, taking care to avoid cornices at the tops of cliffs and to avoid steep, avalanche-prone slopes. All the alpine skiers, cross-country skiers, snowshoers, and even a woman in high heels were having a good time on Hurricane Ridge. Well, except, perhaps, for the woman coming down off the slope borne by a snowmobile, whose leg was in a splint. Perhaps she later sought help from Dr. Gouge, an orthopaedic surgeon from Port Angeles who had a sign advertising his services on the side of a van parked at Hurricane Ridge.
The snow depth gauge on Hurricane Ridge measured 14 feet of snow
Olympic National Park is among the few national parks with an alpine ski area; a rope tow leads to the ridge
Note the record snowfall and the accumulated snow this winter (much more has fallen since)
Snow level rising on the windows of the Visitor Center
Tall, thin conifers are the rule here; a tree with a lot of wide branches would pick up too heavy a snow load, and branches would break
Karen Rentz snowshoeing into the rime ice forest
Rime ice coated the structure of this walkway window outside the Visitor Center
Another view showing thick accumulation of rime ice
Young men marveling at and photographing the rime ice
Looking north from Hurricane Ridge toward the Strait of Juan de Fuca and Vancouver Island in the distance
Wave shape of a cornice atop a cliff on Hurricane Ridge
A pair of conifers covered with ice
Lone tree coated with ice; with a view of the Olympic Range
For more information about Olympic National Park, go to: http://www.nps.gov/Olym/index.htm
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