Note: This was written on battery, in the dark, during the obligatory post-snowfall power outage at Chaos Central.
The folks who live on the Great Plains and along the Great Lakes snicker a bit at news reports on the mass closures in Seattle when snow comes to the the Puget Sound region. Of course, the standard excuse is, “It doesn’t snow that much here, so we don’t have enough snow removal equipment.” But, wait, there’s more…
Most of us live in the Pacific Northwest because of the geography and the climate. The climate is temperate, with few days below freezing in the winter and few days in the 90s in the summer. Most of us live within 20 miles of either salt water or a fresh-water lake. If you want snow, you can find it in the nearby Olympic or Cascade mountain ranges, 12 months out of the year. The rest of the year, the lush green mountains invite backpackers, the flat river valleys attract bicyclists, lakes and estuaries fill with kayakers and canoeists, rivers with rafters, and the larger lakes and the Salish Sea (the accepted name for the inland sea that stretches from Olympia, Washington to Prince Rupert, BC, bounded by the Olympic Peninsula and Vancouver Island) fills with sailboats and motor craft of all sizes.
For all of this, we are willing to put up with the moisture that is a natural consequence of air warmed by the Pacific ocean currents flowing up the coast from the south. Rainwear is a fashion statement, and umbrellas are considered a mostly ineffective and cumbersome nuisance in a land where the average day ranges between swirling mist that clings to everything and fire-hose-like sideways blasts with downpours so heavy that motorists have to brake for migrating salmon. And, for a few days every odd year or so, cold and wet coincide in a heavy snowfall like those that come in waves winter-long in places like Minneapolis and Chicago. But, this is not the midwest.
First, because of the geography: the region is characterized by foothills of the mountain ranges that frame the inland sea. The foothills give way to steep bluffs of glacial till that fall off sharply into the river valleys and sea, up which rise city grids on double-digit grades more suited to Olympic ski jump ramps than walking, driving, or pedaling. And second, because of the climate: the temperate nature of the climate dictates that, when the temperature does dip to the low end of the range, it hovers back and forth across the freezing line. The mass of the inland sea also helps moderate the temperature: when the wind is calm, the snow level is measured in not less than a couple hundred feet above sea level. But, the wind is never that calm, which means the rain that falls on the lower elevations, itself barely melted snow, falls on frozen snow, and therein lies the root of the problem.
Steep slopes plus ice plus a preponderance of evergreen foilage combine for interesting times. The foilage includes firs, pine, and cedar, which are better-adapted to snowy conditions but less so to strong winds, since the wet climate promotes shallow root structures. Other temperate evergreens include broad-leaf plants like the native rhododendron, holly, and other ornamental shrubs found in cities. Deciduous trees in cities tend to become infested with English ivy and other climbing evergreen vines, which make them vulnerable to wind and snowload as well.
So, in the aftermath of one of these snow episodes, the snow plowing efforts, inadequate to begin with, leave many streets unplowed and packed down by adventuresome traffic. Trees are heavy with snow. And then, it rains. At first, since snow is an insulator, the rain simply combines with the snow to form a heavy crust of ice on top of a fluffy layer of loosely-packed flakes. This results in two different effects: first, the leaves and needles of the trees hold the snowballs in place until they become ice balls, at which point the tree either breaks apart or falls over, usually on a power line. Buildings designed for “normal” snow loads may collapse as well as the ice builds up. Second, on steep slopes where there are no trees (because this happens often enough to discourage their growth), the weight of the ice overcomes the integrity of the fluff beneath, and the whole mass heads downhill, picking up speed and mass as it goes, sweeping everything and everyone before it, often ending up in a solid mass of lumpy ice and boulders across a major highway.
While major power transmission lines have usually been built well clear of historic avalanche zones, the metropolitan and rural power grids are not so fortunate, being in the midst of so many snow and ice-laden trees: power outages soon follow, lasting anywhere from several hours to several days, depending on the distance from the substation to the consumer. Getting to the site of the outage to repair the damage or getting to a location where there is power is also problematic. Where the roads have been plowed and walkways shoveled, the rain freezes directly on the surface, creating a virtually frictionless surface not suitable for either walking or driving. New power outages crop up where cars skid off icy roads into power poles or trees.
Meanwhile, the temperature continues to rise, and the snow level moves higher, leaving behind a slushy mixture that begins to be more water than ice. The water moves downhill: the ice holds it back. Water backs up into basements and garages and fills dips in streets and roadways. Then, it all ends up suddenly in streams and rivers, which quickly overflow onto low-lying areas that may have been spared the heavy snow and ice loads but now find themselves underwater.
If the snow load was large enough and the rains continue, the clay bluffs continue to absorb water until they, too, become too heavy and slippery, and the hillsides collapse into the bays, taking trees, houses, and roads with them. Fortunately, the combination of wet and cold winters happen only once a decade or two in this area, so people rebuild and forget the troubles by the next sunny day when the “mountains are out” and they head for the beaches, marinas, backroads, or trails.
