Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Wed Aug 16 2017 Valid 00Z Thu Aug 17 2017 - 00Z Sat Aug 19 2017 ...A storm system will bring showers and thunderstorms across the eastern U.S.... A low pressure system currently developing over the central Plains is forecast to intensify as it heads northeastward into the Great Lakes by Thursday night. Showers and thunderstorms will be focused near and just ahead of the associated frontal systems. The best dynamics associated with the storm are expected to move eastward across the central Plains ahead of the cold front, and across the upper Midwest ahead of the low pressure center through tonight. Some of these thunderstorms are forecast to reach severe levels with heavy downpours, which could lead to the possibility of flash flooding through night. The bulk of the rain should move into Canada on Thursday as the storm center moves into Ontario. However, showers and thunderstorms associated with the trailing cold front will move into the Ohio Valley before reaching the Appalachians on Thursday. Farther east, return flow from the south will bring tropical moisture northward into the Mid-Atlantic region on Friday. The possibility of strong thunderstorms with heavy rain will be further increased as the cold front approaches from the west by Friday afternoon across the entire Mid-Atlantic. Meanwhile, showers and thunderstorms will spread northeastward into New England during the day on Friday. Behind this storm, cooler and drier air will filter into the northern Plains on Thursday, reaching the Midwest and Ohio Valley on Friday. A weak frontal system will help trigger showers and thunderstorms over the central High Plains Thursday night into Friday where some locally heavy downpours are possible. Out West, some scattered thunderstorms can be expected from the Great Basin eastward into the central Rockies as a weak upper-level disturbance moves across. Otherwise, much of the rest of the western U.S. should remain rain-free through Friday with temperatures 5 to 10 degrees above normal in the Pacific Northwest and northern Rockies. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php