Heavy rainfall and severe thunderstorm chances extend from the southernHigh Plains to the lower Mississippi Valley over the next few days......Wet and cool conditions forecast across the Great Lakes, Mid-Atlantic,and Northeast this weekend......Well above average temperatures expected throughout the West andnorth-central United States...After a brief lull, active weather is anticipated to return to thesouthern Plains tonight before spreading into the central/western GulfCoast and lower Mississippi Valley through early next week. A closedupper-low over the Southwest and lingering frontal boundary extending fromthe Gulf of Mexico to the southern Rockies is expected to be the triggerfor developing thunderstorms this evening. Isolated strong storms mayoccur from southeast New Mexico to West Texas, with the potential forlarge hail, strong wind gusts, and localized flash flooding. Unsettledweather is also forecast to stretch into the central Rockies and centralHigh Plains. By Sunday, the aforementioned upper low is forecast to slideeastward into the central Plains and shift thunderstorm chances eastwardthroughout much of Texas and the lower Mississippi Valley. However, thegreatest threat with these storms are likely to be associated with flashflooding, particularly throughout parts of eastern and north-centralTexas. Saturated ground conditions and additional heavy rain may lead tonumerous instances of flash flooding, with Waco, Texas and points eastwardto near the Louisiana border under a Moderate Risk (level 3/4) ofExcessive Rainfall on Sunday. Showers and thunderstorms are then forecastto shift toward the central/western Gulf Coast and lower MississippiValley, producing additional chances for flash flooding and severeweather. Meanwhile, the northern end of the precipitation shield isforecast to push ahead of a low pressure system swinging from the southernPlains to the mid-Mississippi Valley, with a few inches of rain possibleinto Kansas and Missouri by the end of the weekend.Unsettled weather may also dampen weekend plans from the Great Lakes tothe Mid-Atlantic and Northeast, as well the northern Plains. A lowpressure system tracking from the lower Great Lakes this evening to theMid-Atlantic coastline Sunday afternoon will spread showers across theregion, while also keeping temperatures on the cooler side. Further west,a lingering frontal boundary may spawn scattered thunderstorms across thenorthern Plains on Sunday.A taste of summer is expected to continue for some folks as well aboveaverage temperatures stretch from the West to the Midwest on Mother's Day.Highs in the 70s and 80s will be widespread (90s in the Southwest), withabove average temperatures also impacting southern Texas and Florida intoMonday.