A front is the boundary between two air masses. As a cold front passes, colder, drier air arrives: pressure that has been falling turns to rise, and the temperature and dew point drop, often with a gust and a burst of rain. A warm front brings milder, moister air, usually after hours of falling pressure and rain.

These are found automatically from this station's readings alone, by looking for those changes beyond what's usual for the time of day and year. So they're "likely": some fronts will be missed, and now and then a heavy shower may look like one.