Typically, when a low pressure front is coming (and they do, all the time) it signals not only a change in the weather, but a drop in the barometric pressure, which is pressure against the Earth's atmosphere. She actually knew this because of what happens to our bodies when the barometric pressure changes.
Similarly, what does it mean when the barometer is low?
A barometer measures air pressure: A "rising" barometer indicates increasing air pressure; a "falling" barometer indicates decreasing air pressure. Therefore, on any given day you would expect the air over a desert to have a lower pressure than the air over an ice cap.
What happens when there is a drop in barometric pressure?
Weather. Weather patterns are a common cause in barometric pressure drops. When low-pressure weather systems move in over a certain area, not only is pressure in the atmosphere shifted, but it causes the barometric pressure reading to drop. A low-pressure system indicates that low-pressure air rises and begins to cool.
Why does the barometric pressure drop when there is a storm?
Because hot air is less dense than cold air, and when hot and cold air collide, the hot air is forced to rise over the colder air. When the warm air is forced up, it causes surface air pressure to drop, sort of like having a small vacuum develop at the earth's surface at the boundary between the two air masses.