It feels like summer along the Colorado Front Range today, with high temperatures expected to reach the upper seventies. But, if you open your eyes, you will find that it is still November. The trees and shrubs are mostly leafless and those leaves that still flutter in the breeze have lost their October glory. Most noticeable is the lighting, the effect of the low, seasonal sun angle, which produces long shadows and less intense sunlight.
For those interested enough to notice, the summer songbirds are absent and a mix of winter visitors and permanent residents feed in the thickets and woodlands. Here on our Littleton farm, there are no house wrens buzzing about the brush pile or colorful orioles moving among the mulberries; rather, juncos have arrived to join the chickadees, house finches, flickers, magpies and other regulars. Canada geese, much more common during the colder months, are another sign of the season, their noisy flocks moving about the area from dawn to dusk.
This brief heat wave, a common occurrence along the Front Range, is due to two factors. The current jet stream pattern has produced a high pressure ridge over the western U.S., allowing warm air to move up from the Desert Southwest. Augmenting this effect, the southwest winds descend on the east side of the Continental Divide; as air is forced to descend, it compresses, dries out and heats up. These chinook winds produce periods of mild weather throughout the winter and cause heavy snows to melt rapidly (unlike the persistent snowpack of the Upper Midwest and Northeast). Lest I dwell too much on the fabulous Colorado climate, it is important to note that the ridge is expected to break down within two days; the jet stream will dip and cold, Canadian air will pour south across the region.
