Yesterday, I wrote about a ski trip in Stehekin Valley’s ample snow. Since I took that trip a few days ago, more snow has fallen. A lot more.
This was the scene I woke to yesterday.
And, snow was slowly enveloping the neighbor’s house.
This is nothing abnormal for the region, and in many way’s it is expected. In winter, the jet stream over Alaska and Canada shifts south over the Pacific Ocean. Air masses traveling across the Pacific at this time of the year are “immodestly moistened,” as Daniel Matthews describes in Cascade-Olympic Natural History, bringing heavy precipitation to Washington, Oregon and California. The Cascade Mountains and Sierra Nevada are effective moisture traps for these storms. When storms encounter the mountains, the air rises and cools causing it to precipitate its moisture. The Stehekin Valley in Lake Chelan National Recreation lies east of the Cascade Crest, so the area experiences drier weather than the wetter Skagit River valley to the west. However, the valley is not far enough east to experience the Cascades’ full rain shadow, hence the ample snowfall recently.
In my estimation, at least three feet (approximately 50-100 cm) of snow has accumulated over the past five days, much of it falling in the last 24 hours. Higher elevations certainly gained more. I was curious to know the exact snow depth near my house, which lies at a modest 1100 feet (335 meters). After the snowfall abated yesterday afternoon I got out the snow shovel prepared to dig in.
I chose to measure the snow out in a small meadow away from the influence of trees, but getting there took some effort. The first few feet of snow was very soft. The base to stand on, if you could call it that, was well under the surface.
After floundering my way into the meadow, I started digging…
…and digging and digging until I reached the soil.
The pit was over 65 inches (166 cm) deep!
Long time residents describe winters with lots of snow and occasional rain too. Rain compacts the snow, increasing its density but decreasing its depth. This winter, I’m told, is a bit of an exception with lots of snow, but without temperatures warm enough for the occasional rain storm.
Winter snowfall is essential to the well being of millions of people across the West, especially farmers who cannot depend on summer rain to sustain crops. Snowmelt in rivers quenches the thirst of residents in Los Angeles, Las Vegas, Phoenix, Salt Lake City, and many, many other places. It’s a reservoir, slowly releasing its water in spring and summer when it is needed most.
Climate models indicate changing weather patterns will come to the West as temperatures rise. The North Cascades region won’t be without snow, but changes will be felt, and in a lot of ways the region is already experiencing them. More rain will fall and less snow will collect on the mountains. At first this may seem insignificant. However, this will change the timing and duration of peak stream flows. Currently, stream discharges peak in the spring and early summer when snowmelt is heaviest. The pattern seems to be shifting toward more frequent peak flows in spring and fall. Rain on snow events can cause heavy flooding, damaging roads and homes. (Stehekin River has experienced three 100 year floods since 1995.) Warmer springs temperatures melt snow faster, affecting sensitive habitats like montane wetlands, places that harbor sensitive species like the Cascades frog. Soils dry faster without snow too, increasing the risk of wildfire.
Snow is often viewed as an annoyance or danger, delaying and restricting travel, but it is a key component of ecosystems where it occurs. Snow on mountains is a water tower, one we can’t afford to lose. (It’s also a lot of fun to play in.)