October 24, 2010 in Idaho Voices

We’re overdue for stormy weather

Michelle Boss
 

We knew it couldn’t last forever. The first three weeks of October turned out warmer than average (by about 3.3 degrees F), with some nice long stretches of mild, sunny days. The first widespread freeze occurred about 11 days later than average, giving gardeners a few extra days to harvest those frost sensitive veggies.

However computer forecast models are finally showing a significant change in the weather pattern, from the ridge we’ve been enjoying, to a stormier pattern of cold troughs. Snow levels will be dropping, with a good chance we’ll start seeing some white in the mountains. As far as lower elevations snows, Coeur d’Alene only averages 0.2 inches of snow for the month of October. In Spokane, average October snow is only 0.4 inches.

You’ve probably noticed that along with the cooler temperatures we’re having, that it sure has been getting dark a lot earlier these days. Official sunset times are now well before 6 p.m., and I wanted to give you a heads-up that daylight saving time will be ending the first Sunday of November this year, Nov. 7. Daylight saving time was extended by four weeks starting in 2007, with the hopes of squeezing out more energy savings. There are no statistics on whether that has been realized or not.

This week I want to briefly touch on the subject of high and low pressure systems. While meteorologists use terms like surface low and upper level low pressure all the time, I’m guessing that the general public has no idea why there is a distinction.

When looking at the atmosphere, a meteorologist is not only concerned with what is going on in the horizontal plane near the ground, but also what goes on in the depths of the atmosphere as you rise in elevation. In a typical storm system, we may refer to an area or trough of low pressure and its accompanying warm and cold fronts on the surface. It is along and ahead of these surface fronts that we might see storms and/or general precipitation.

These systems are usually tilted toward the west in the vertical, however, so that the area of low pressure on the surface may be over the Inland Northwest, while the “upper level” low pressure is located over the Cascades. It’s kind of like a one-two punch of a storm. Just because the cold front/surface low has pushed east, doesn’t mean we’re out of the woods yet. The upper level low that comes afterward indicates a pool of colder air aloft. With adequate heating at the surface, an unstable environment is created which can lead to everything from more showers to even funnel clouds.

Michelle can be reached at weatherboss@comcast.net.

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