Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Wed May 16 2018 Valid 00Z Thu May 17 2018 - 00Z Sat May 19 2018 ...A wet and stormy pattern will continue over much of the eastern U.S., with flash flooding and strong thunderstorms possible over southern New England and the northern Mid-Atlantic states... ...An active pattern is expected over the northwestern quarter of the Nation the next few days... ...Shower and thunderstorm activity will be possible for portions of the Great Plains, with severe thunderstorms possible Thursday and Friday... Parts of the Eastern U.S. from the Deep South to the Mid-Atlantic will stay in a persistent wet and stormy pattern through the rest of the week as tropical moisture out of the Gulf of Mexico interacts with a nearly stationary frontal boundary. The best chance for heavy to excessive rainfall will be across parts of the central Appalachians and the Mid-Atlantic region near a weak disturbance lifting northward across the central Gulf Coast states and into the Tennessee Valley. WPC has highlighted this region in a slight risk for excessive rainfall from tonight through early Friday. Scattered to widespread showers and thunderstorms will likely develop across the central/northern High Plains by Thursday afternoon as upper level energy slides through aloft. Conditions may be favorable for severe thunderstorms to develop, and the Storm Prediction Center has this region in a slight risk for severe weather on Thursday and Friday.Also, heavy rainfall will also be likely within this area of convection. WPC has broad area of marginal risk across the Plains with slight risks focusing over southern North Dakota and western Nebraska. An active pattern is expected over the northwestern quarter of the Nation the next few days as a weakening upper low lifts northeastward of the central Great Basin and an upstream upper low begins to edge inland over California. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php