Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Sun Sep 18 2016 Valid 12Z Sun Sep 18 2016 - 12Z Tue Sep 20 2016 ...Heavy rain possible across portions of the Appalachians, Mid-Atlantic, and Northeast... ...Warming temperatures expected across the central and eastern U.S... Showers and thunderstorms will be possible ahead of slow moving cold front today and tonight across much of the Appalachians, Mid-Atlantic, and Northeast. Locally heavy rain will be possible. Showers and thunderstorms may persist along the East Coast into Monday morning before becoming more isolated by Monday afternoon. A second frontal system will move from the northern High Plains into the Upper Midwest today. The system will be relatively starved for moisture, so only scattered showers and thunderstorms will accompany it. On Monday this front will move east across the Great Lakes, with scattered showers and thunderstorms possible for those areas. Areas of showers will affect the higher terrain of the Pacific Northwest and northern Intermountain States today, the result of a surface frontal boundary and upper-level disturbance across the region. Farther south, dry conditions will prevail until Monday and Tuesday, when scattered showers and thunderstorms will be possible across the southwestern U.S. as tropical moisture spreads into the region. A building ridge of high pressure across the southern plains will cause temperatures across the central and eastern U.S. to gradually increase through the next couple days. By Monday and Tuesday, high temperatures are forecast to be 5 to 15 degrees above average across much of the central and eastern U.S. An upper-level low centered along the Mid-Atlantic/Southeast coast may keep temperatures in coastal areas in those regions closer to seasonal averages. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php