Today: Excessive rainfall will be likely across portions of the West Coast of the United States. Elsewhere, an area of high pressure located across the eastern United States will begin to move offshore as a low continues to move eastward and take its place. The low will bring the threat for light to moderate rainfall and possibly some isolated thunderstorms across much of the Great Lakes region, Northeast, and Mid-Atlantic states throughout the day today. Further north, snowfall will be possible behind the system in Canada and across the northern Great Lakes region. Further west, high pressure will build in behind this low, which will bring fair conditions over much of the Plains states.