If you've ever tuned in to hear your local weatherman, checked the Internet or watched the skies before shoving-off–and every boater should–you've heard about weather fronts.

That's because fronts–defined in layman's terms as a transition between two air masses–produce the kind of unsettled skies and rocky seas that can make life difficult for boaters.

Understanding how these weather fronts work, and their impact on clouds, rain and wind, is perhaps the best way to stay ahead of the weather. While nobody can predict Mother Nature's whims all of the time, understanding how fronts interact will give you some indication of the weather heading your way and how to prepare. At a minimum, you will know when to break out the foul weather gear–or when to head for port.

COLD FRONTS

The air that surrounds the Earth is always changing. Air masses of differing temperature and humidity are in constant motion, and not all of them readily mix with one another.

When two dissimilar air masses meet, hot air rises above cold air causing the formation of a storm front. This front, while represented by a single line on a weather map, is actually a transition zone that can stretch from five to 60 miles. Inside the front, heavy cold air masses advance at speeds ranging from 10 to 50 knots–faster in winter and slower in summer–while warm air masses advance more slowly at speeds of 12 to 15 knots.

When a cold air mass pushes against a warm air mass, it's called a cold front. The cold air forces the warm air skyward, where it cools and produces rain. Cold fronts are most likely to produce thunderstorms, including dangerous squalls that can appear from 100 to 300 miles ahead of the front itself. (For a story on thunderstorms, see link below.)

While no one can predict the weather with 100 percent accuracy, there are patterns that are useful to know. Normal air circulation in the northern hemisphere travels clockwise, so the wind on the western side of the warm air mass moves south or south-east. On the eastern side of the cold air mass, the wind will generally move north or north-west. Weathermen call this "anti-cyclonic" movement.

When a cold front strikes, it's marked by a series of events that evolve over a 24-hour period. They begin as wind picks up from the south or southwest. As barometric pressure begins to fall, clouds will sink lower in the sky, thunderheads will form and wind and rain will intensify.