There is one truism that I recall from flying and working with Richard Collins when he was editor in chief of Flying. At least in the eastern half of North America, if the wind is more southerly than forecast, or stronger out of the south than was predicted, the weather is going to be worse than expected. The principle is elegantly simple, and almost always on the money. Warm moist air is a weather maker, and in this part of the world it comes from the Gulf of Mexico. When nature conspires to push more of this warm, moist air northward, it is likely that we're in for what usually happens when hot, wet air meets cooler, dry air. The two air masses will either duke it out in convective activity, or they'll mush together in a warm front that is bound to bring low ceilings and rotten visibility.