Weather forecast for tonight: dark. Continued dark overnight, with widely scattered light by morning.

~ George Carlin

If all weather forecasting was so simple. Such information – from TV, radio or online – is kept basic. Going much beyond this point would leave most of us lay persons in the dust. One meteorological term often used is also the least understood: barometric pressure. Is it high or low? For that matter, what in the heck is it?

Look up at the sky and try to imagine the weight of the atmosphere: the huge amount of gas surrounding our planet and pulled to its surface by gravity. All that gas might look like a vast, empty cloud of nothing, but it still has weight. It might feel like nothing to you and me, but it is considerably heavy – about 14.7 pounds pressing on every inch of our body. We don’t notice it because we are used to it.

Some areas have more pressure than their surroundings and some areas have less. Those that have less pressure are called low-pressure systems. Low-pressure systems “suck” air into them. A difference in pressure areas generally creates winds and undesirable weather. High pressure systems, on the other hand, have more air pressure than their surroundings. That means they are constantly pushing air away from them into the areas that have lower pressure. They are often associated with clear blue skies.

Mother Nature likes everything to be fair and equal; this pertains to air pressure as well. Weather is created in her attempt to do so.

The difference between high pressure and low pressure is experienced in the air surrounding; i.e., the weather. In low pressure, there is a rise in the air and it cools down. The moisture condenses, which causes clouds. Whereas in high pressure the air starts to sink and it warms up. High equals good weather. Low equals bad weather. Now, that’s a matter of opinion!

Some of nature’s signs cannot be understood simply by observing them but require tools to measure. Evangelista Torricelli invented such a tool: the barometer. He made the first barometer in Florence, Italy in 1644. With the atmospheric pressure can be measured, which can provide information pertaining to current weather and weather that is just around the corner.

Summertime winter heat for now. Come Monday a significant cooling trend settles in as a fairly cold low drops through Nevada and the Colorado River Valley. High temperatures are predicted to drop by at least 10-15 degrees for the valleys. A marine-based light rain is possible on Tuesday. Be on the safe side; keep both a bathing suit and umbrella close at hand!