Sun may make appearance but it’ll still be cold

In the last couple of weeks we’ve had to endure some long stretches of dreary weather with little to no sun. Many times the weather map showed high pressure in place, and you might have wondered why conditions stayed so gray. High pressure equals sunny weather right?

High pressure is usually an indicator of sinking air, which doesn’t lend itself to stormy weather because air has to be rising for storms to occur. High pressure doesn’t always guarantee sunny skies, though. If the lower atmosphere is moist due to the evaporation of snowmelt, we often get socked in with low clouds and fog. It won’t rain or snow, though drizzle/flurries are not out of the question. Winds will be light to calm, and unfortunately the sun can be kept at bay for days.

The best clearing in the wintertime comes when dry, northerly winds spread across the Inland Northwest behind a strong cold-front, … usually an arctic front. The air stays chilly, but an influx of dry air keeps the fog and low clouds from forming.

Of course in the middle of winter, I can never seem to get my kids to understand how it can be sunny outside and not warm. It would seem like a perfectly logical conclusion. The sun heats the Earth, the sun is shining, therefore we can go outside in our swimsuits.

If I really wanted to confuse them, I could also tell them that the Earth is actually closer to the sun (by about 3 million miles) during the Northern Hemisphere’s winter. The fact that you can have “lots” of sun and still feel bone-chilling temperatures must mean that something more than the mere presence of sunshine dictates the air temperature.

In Anchorage, Alaska, which is in the south-central part of the state, they receive 19.5 hours of sunlight on the summer solstice. Average summertime highs are only in the mid-60s, though. The angle of the sun’s rays must be the key to how much warming occurs at any given location.

Remember from early science classes that the Earth is tilted on its axis. This is the reason we experience different seasons. In the Northern Hemisphere, we are tilted toward the sun in the summer and away from the sun in the winter. Even on a winter day full of sunshine, the sun remains relatively low on the horizon when compared with summer. Because of that, the sun’s rays are not as direct and must pass through a thicker layer of our atmosphere before reaching the ground.

You can replicate this effect by shining a flashlight against the wall straight on, and then again at an angle. The light is much more intense when shined straight on. In the wintertime when the ground is snow covered, we lose even more of the sun’s heat because the snow does a good job reflecting the light. We say that the snow has a high albedo, or reflectivity.

To further the cooling effect, heat energy from the sun is also lost when it is used to melt the snow rather than warm the ground. The bottom line is, you’re probably going to need that winter coat no matter how much sun you see outside. The record high for Coeur d’Alene for the entire month of February is only 62 degrees, which occurred on Feb. 24, 1981. In the middle of winter it would be more likely that a warm wind, not just a bright sky, would be needed to make that happen again.