Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 354 AM EDT Wed Aug 14 2019 Valid 12Z Wed Aug 14 2019 - 12Z Fri Aug 16 2019 ...Numerous showers and thunderstorms along the Gulf Coast and the Southeast U.S., and building heat across 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 over 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 storms from the central Plains and also near the southeast coast. The central Plains will appear to have the best prospects for strong to severe thunderstorms for the next couple of days. The frontal boundaries are expected to move rather slowly through Thursday as they merge over the eastern U.S. This pattern will promote unsettled weather along the Southeast U.S. and the Florida Peninsula. Gradual improvement in the weather is expected for the Ohio and Tennessee Valleys. 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 through the middle of the week 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. Hamrick/Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php