Although temperatures are warming up as May and June progress, colder weather systems in Canada are still quite active. These often move into the Great Lakes region and the Northeast United States and trigger lines of showers and thunderstorms. This activity makes these systems quite important, especially as moisture flows northward from warmer tropical regions. Not only will we see how these systems appear on the surface chart, but we'll also be taking a close look at the polar front jet to understand how the two interact.
TIM VASQUEZ is a former Air Force forecaster and author of Digital Atmosphere, a weather forecasting software program. He lives near Norman, Oklahoma, where he keeps busy as a weather consultant and software developer.