National Weather Service Chicago/Romeoville IL
8:48 PM Friday August 18.
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the wave, along with the average height of the highest 10% of the waves which will occasionally be encountered. synopsis, low pressure of 29.5 inches moving into southern quebec will lift east of james bay saturday and continue across northern quebec sunday. a ridge averaging 30.0 inches stretches along the mississippi valley will spread across much of the midwest saturday. low pressure of 29.8 inches will form over the central great plains this weekend and remain there through tuesday while another low of 29.5 inches moves from northern manitoba saturday to quebec tuesday as a trailing cold front sweeps south across lake michigan.