Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Wed Aug 14 2019 Valid 00Z Thu Aug 15 2019 - 00Z Sat Aug 17 2019 ...Numerous showers and thunderstorms along the Gulf Coast, the Southeast U.S, and into the Mid-Atlantic... ...Scattered strong to severe thunderstorms are expected to spread eastward across the central Plains... ...Excessive heat expected to continue for a couple more days over the Desert Southwest... A general zonal type upper air pattern is expected to prevail across the U.S. for the next few days, with more upper level ridging over the Southwest and a broad trough across the Great Lakes. This will keep temperatures generally below normal across the northern tier states while above normal temperatures will continue across much of the South, Southeast, as well as the western U.S. A couple of frontal boundaries separating the relatively cooler weather across the northern U.S. and the hot and humid conditions across the South will provide a focusing mechanism for organized showers and thunderstorms across the central Plains for the next couple of days. A low pressure center is forecast to form near the front over the central High Plains tonight and move toward the northeast on Thursday. This will enhance the chance of strong to severe thunderstorms over the central High Plains tonight, spreading eastward toward the Midwest by Friday. The rain could be heavy enough to result in localized flash flooding in parts of the area. Farther east, the frontal boundaries are expected to move rather slowly as they merge along the Eastern Seaboard. This pattern will promote unsettled weather from the Gulf Coast to the Southeast U.S. and up into the Mid-Atlantic. Gradual improvement in the weather is expected for the Ohio and Tennessee Valleys behind the frontal boundaries. While the heat will be abating some from the south central to southeast U.S. this week compared to recent days, it will be building across the Southwest for the next couple of days as the upper level ridge builds westward. An excessive heat warning is in effect for the lower elevations of southern Arizona to central California for afternoon high temperatures in the 105 to 115 degree range, and overnight lows only in the middle 80s to near 90 degrees for the warmest locations. Heat advisories are in effect for locations closer to the coast for central and southern California. The hot temperatures across the Southwest are expected to continue through the remainder of this week. Kong/Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php