Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 332 AM EDT Fri Jun 26 2015 Valid 12Z Fri Jun 26 2015 - 12Z Sun Jun 28 2015 ...Severe thunderstorms and flash flooding possible for portions of the central and eastern U.S... ...Hot temperatures expected for much of the western U.S... A major pattern change is in store for much of the central and eastern U.S. over the next few days as a deep upper-level low digs into the Great Lakes. A quasi-stationary surface frontal boundary is in place early this morning from the Mid-Atlantic across the Ohio valley and into the central plains. Weak waves of low pressure moving along the front will continue to result in areas of showers and thunderstorms through today. By late today into tonight -- as the upper-level low deepens over the Great Lakes -- a much stronger wave of low pressure will begin to develop along the surface front across the Ohio valley. Numerous showers and thunderstorms are expected from the Ohio valley and central Appalachians west into the middle Mississippi valley today in association with this system. On Saturday the low pressure system will cross the Appalachians and move into the Mid-Atlantic region. Numerous showers and thunderstorms are again expected on Saturday for much of the eastern U.S. Severe thunderstorms are possible from the central plains eastward across the Ohio valley and into potions of the Mid-Atlantic region. Please refer to products issued by the Storm Prediction Center for further information on the threat of severe weather. In addition to severe weather, heavy rainfall will be associated with thunderstorms, and flash flooding is possible in some areas. As a result of cooler temperatures associated with the upper-level low, temperatures will be 5 to 15 degrees below average across the Great Lakes and Northeast. A strong ridge of high pressure at the mid and upper-levels of the atmosphere will expand across the western U.S. over the next couple days. Sinking air in association with this ridge will result in well above average temperatures for much of the west, with little in the way of rainfall. Afternoon high temperatures are forecast to rise well into the 90s across much of the interior West, with temperatures in the 100s forecast for some areas. These high temperatures will be 15-25 degrees above average in some areas of the Northwest. Scattered showers and thunderstorms will be possible across the Desert Southwest Saturday afternoon as some moisture from the Gulf of Mexico moves into the area. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php