Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 353 AM EDT Fri Jul 28 2017 Valid 12Z Fri Jul 28 2017 - 12Z Sun Jul 30 2017 ...Heavy rain for parts of the East Coast through Saturday, followed by cooler conditions over the weekend... The stage is set for a storm system more typical of autumn to form over the Mid-Atlantic Friday into Saturday. This system is currently at its formative stage across the Ohio Valley as a couple of low pressure waves ride along a cold front. As the cooler air mass behind the cold front continues to filter into the northern U.S., an upper-level trough is forecast to form over the Great Lakes and interact with the low pressure waves along the cold front. This will lead to the intensification of a low pressure system over the mid-Atlantic region late Friday into Saturday, with some similarities to a cool season nor'easter. Rain is expected to become heavy Friday night along with gusty winds, especially along the coast. The potential exists for 2 to 5 inches of rain to fall from the central Appalachians eastward to the northern Mid-Atlantic coast through Saturday, with some flash flooding possible in areas that receive repeated rounds of thunderstorm activity. In the wake of the storm, temperatures will likely be cooler than average for a few days. Parts of the Desert Southwest, Four Corners, central/southern Rockies and into the central High Plains will also have scattered showers and thunderstorms as monsoonal moisture interacts with a weak frontal boundary over the western High Plains. It appears that eastern Colorado and northern New Mexico will get the greatest rainfall totals, with a few instances of flash flooding possible. Across the southern Rockies, much of the initial thunderstorm activity should congregate across the local mountain ranges before migrating toward the valley floors and the central High Plains. Hamrick/Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php