Many pilots tend to focus much of their weather analysis time on surface weather reports and surface forecasts. This includes the surface analysis chart, prog charts, surface observations and even terminal forecasts. But they don't take the time to look at the upper level or constant pressure charts. Much of the energy in the atmosphere is aloft and there are many scenarios that require you to examine the upper-level weather to completely understand what weather to expect along your proposed route of flight.
For example, this morning there was a strong cold front that was slowly moving southeast through the eastern U.S. bringing a solid line of showers and thunderstorms along and head of this cold front shown on this 15Z surface analysis above. There's an area of high pressure moving in behind this front, but would you expect convection in and around the area of Lakes Ontario and Erie well behind the cold front by simply looking at the surface chart?
Actually, this morning there were two convective SIGMETs just downwind of both lakes consisting of an area of showers and thunderstorms as shown above on the EZWxBrief EZMap display. What is causing this convection? Well, in order to understand this better, you need to look aloft at the 500 mb constant pressure chart.