Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Sep 28 2016 Valid 12Z Wed Sep 28 2016 - 12Z Fri Sep 30 2016 ...Heavy rain expected across the Mid-Atlantic region and central Appalachians... ...Scattered showers and thunderstorms will be possible over the Southwest and southern Rockies... The biggest weather story across the continental U.S. through the end of the week will be a large upper level low that is forecast to track slowly across the Great Lakes and then the Ohio Valley. Cool conditions and numerous showers are expected in the vicinity of this low with an unstable atmosphere in place. It will certainly feel like fall across these areas. Things get more interesting east of this upper low across the central Appalachians and the Mid-Atlantic region. By Wednesday night, increasing amounts of Atlantic moisture wrapping northwestward ahead of this system will lead to a heavy rain event from Virginia to Pennsylvania as it interacts with a surface boundary lingering over the region. Rainfall totals within this moisture plume could be on the order of 3 to 6 inches for some areas, especially where heavy showers and thunderstorm activity develop repeatedly over the same areas, and this could lead to flooding issues. Elsewhere across the nation, conditions will be mostly sunny and pleasant across much of the central U.S. and extending westward towards the northern Rocky Mountains with surface high pressure governing the weather pattern. Across the western U.S., modest moisture combined with weak shortwave energy aloft should support the development of afternoon showers and thunderstorms over portions of the Southwest and southern Rockies through Friday. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php