A heat wave begins to settle in over the Great Lakes, Ohio Valley andthe Northeast today, continuing through midweek...Significant heavy rain/flash flooding threat for the Texas Gulf Coastlater Tuesday and especially Wednesday associated with Potential T.C.One.Heavy rain and severe thunderstorms possible Tuesday/Wednesday from theUpper Midwest into the Central Plains...Late-season wet snow will persist across the high-elevations of thenorthern Rockies for the next couple of days...An active w...