Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 PM EDT Sun Jun 21 2015 Valid 00Z Mon Jun 22 2015 - 00Z Wed Jun 24 2015 ...Severe thunderstorms and flash flooding possible across portions of the northern and central plains, Midwest, Ohio River valley, and central Appalachians... ...Above average temperatures expected to continue across much of the contiguous U.S... High pressure at the mid/upper-levels of the atmosphere will expand across the southern tier of the U.S. over the next couple days, keeping the more active weather generally across the northern and central portions of the country. A cold front will cross the northeastern U.S. tonight, bringing scattered showers and thunderstorms. This frontal boundary extends westward across the central Appalachians and into the Ohio valley and middle Mississippi valley, and is forecast to stall tonight before beginning to move northward as a warm front on Monday. This boundary will keep chances of showers and thunderstorms in the forecast for the Ohio valley and central Appalachians this evening into tonight before shifting northward toward the Great Lakes on Monday. The Storm Prediction Center indicates there is a chance for some storms to become severe along this front through tonight. Please refer to the Convective Outlooks from SPC for the latest details on the threat of severe weather. In addition, heavy rain from thunderstorms may lead to localized flash flooding. A stronger low pressure system is developing across the northern High Plains this afternoon and the surface low is forecast to move across the northern plains toward the Midwest tonight into Monday morning. An area of widespread showers and thunderstorms is forecast to develop across portions of the northern plains this evening, which will then move eastward across the Midwest and into the Great Lakes on Monday. Severe thunderstorms are also possible in association with this system tonight into Monday over a large area from the northern plains to the Midwest and Great Lakes. Heavy rain and flash flooding are also possibilities in these areas as well. The ridge of high pressure aloft building across the southern tier of the country will result in above average temperatures for many areas. Afternoon high temperatures on Monday and Tuesday will range from 5 to 15 degrees above average across much of the interior western U.S., central plains, and much of the eastern U.S. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php