COLUMBIA, S.C. — A viral video on TikTok has many people questioning whether they really know what a 50% chance of rain means. The answer may be more complicated than you think!
The chance of rain is also known as the probability of precipitation, or pops for short. There is an equation that meteorologists use to calculate the probability of precipitation for a certain day. The probability of precipitation is equal to the confidence that it will rain multiplied by the area that will get rain.
It's also important to note that when we say "get rain", it means any accumulations of of at least 0.01".
So what does that look like? Let's take the Midlands of South Carolina, which is the area that we forecast for at WLTX. If I am 80% confidence that 50%, or half, of the viewing area will receive rain on a given day then the pop for that day would be 40%!
On the other hand, If I am 100% confident that tomorrow only 20% of the area will see rain, then that would be a pop of 20%.
It's important to note how this looks on a 7 day forecast! In the short term, say the next 1 or 2 days, our confidence in the forecast is usually pretty high and near 100%. That would mean that the pop you see on the forecast is more representative of the percent of the area that will see rain.
However, looking more long range in the forecast, for example over the 5-7 day range, confidence is usually a bit lower. This would mean that the pop is more representative of a confidence forecast rather than an areal forecast.
So overall the chance for rain can be a bit subjective and can require some more context with it! it's also important to note that a pop or chance of rain does not tell you how long it will rain or how much will fall. For that, you'll need to tune into the forecast!