Why colder air doesn’t just mean a change in temperature
Central Missouri has been dealing with abnormally warm weather for January, as areas like Columbia are off to the 3rd warmest start on average in recorded history. This is set to change soon, though, as a cold front bringing significantly cooler air is set to pass through the region tonight into Wednesday. With this, not only is there a change in the air temperature, but there is also a change in the weight or density of the air.
During the summer or in situations like the abnormally warm air that has been in place over the past couple of days, air molecules are more energetic and have more space to move around, meaning they aren't as tightly packed together. During colder scenarios, such as the one about to take over Central Missouri, the air is not nearly as energetic. This means that the air molecules are more tightly packed together and have less space to move around. This can be thought of as more of a "wall" of air that makes it harder for objects to move through it.
This is why when a cold front moves through, the warm and less dense air is forced over the "wall" of colder air. The warmer air molecules are moved easily compared to the more stubborn cold air, so the cold air often wins out in these scenarios. This will be the case as the cold front from the north enters the area overnight and forces the mild temperatures out of the area along with it.
An example of this dense air creating issues in objects moving through it is golf. On a warmer day like today, a golf ball that is hit is traveling through less dense air that is more freely moving overall. Once colder air takes over, that same drive might end up losing distance. This is because the air molecules are more tightly packed together and are acting like a "wall" that the golf ball has to in turn exert more force on to travel. As the ball fights through a denser crowd of air molecules, drag from the friction of the air itself can lead to shorter drives. This is because it is physically harder to move through the atmosphere in these situations.
Another problem that might arise when this colder, denser air takes over is the loss of pressure in the tires of your car. This is because in warm air situations, the less dense air can take up more space in the tires since it has more energy and freedom to move. When cold air takes over, the air molecules condense and take up less space in the tires, leading to a loss of pressure and eventually your tire pressure lights coming on. This is also why your car might feel peppier but use more gas. Your engine is breathing in that dense, oxygen-rich air, but is also facing more air resistance from the colder air once higher speeds are reached.
